PL/SQL Functions



What is a Function in PL/SQL?

A function is a named PL/SQL Block which is similar to a procedure. The major difference between a procedure and a function is, a function must always return a value, but a procedure may or may not return a value.

General Syntax to create a function is

CREATE [OR REPLACE] FUNCTION function_name [parameters]
RETURN return_datatype;
IS
Declaration_section
BEGIN
Execution_section
Return return_variable;
EXCEPTION
exception section
Return return_variable;
END;
1) Return Type: The header section defines the return type of the function. The return datatype can be any of the oracle datatype like varchar, number etc.
2) The execution and exception section both should return a value which is of the datatype defined in the header section.

For example, let’s create a frunction called ''employer_details_func' similar to the one created in stored proc

1> CREATE OR REPLACE FUNCTION employer_details_func
2> RETURN VARCHAR(20);
3> IS
5> emp_name VARCHAR(20);
6> BEGIN
7> SELECT first_name INTO emp_name
8> FROM emp_tbl WHERE empID = '100';
9> RETURN emp_name;
10> END;
11> /

In the example we are retrieving the ‘first_name’ of employee with empID 100 to variable ‘emp_name’.
The return type of the function is VARCHAR which is declared in line no 2.
The function returns the 'emp_name' which is of type VARCHAR as the return value in line no 9.
How to execute a PL/SQL Function?

A function can be executed in the following ways.

1) Since a function returns a value we can assign it to a 

variable.employee_name := employer_details_func;

If ‘employee_name’ is of datatype varchar we can store the name of the employee by assigning the return type of the function to it.

2) As a part of a SELECT statement

SELECT employer_details_func FROM dual;

3) In a PL/SQL Statements like,

dbms_output.put_line(employer_details_func);

This line displays the value returned by the function.

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PLSQL Stored Procedures

Stored Procedures

What is a Stored Procedure?

A stored procedure or in simple a proc is a named PL/SQL block which performs one or more specific task. This is similar to a procedure in other programming languages.

A procedure has a header and a body. The header consists of the name of the procedure and the parameters or variables passed to the procedure. The body consists or declaration section, execution section and exception section similar to a general PL/SQL Block.

A procedure is similar to an anonymous PL/SQL Block but it is named for repeated usage.

We can pass parameters to procedures in three ways.
1) IN-parameters
2) OUT-parameters
3) IN OUT-parameters

A procedure may or may not return any value.

General Syntax to create a procedure is:

CREATE [OR REPLACE] PROCEDURE proc_name [list of parameters]
IS
Declaration section
BEGIN
Execution section
EXCEPTION
Exception section
END;
IS - marks the beginning of the body of the procedure and is similar to DECLARE in anonymous PL/SQL Blocks. The code between IS and BEGIN forms the Declaration section.

The syntax within the brackets [ ] indicate they are optional. By using CREATE OR REPLACE together the procedure is created if no other procedure with the same name exists or the existing procedure is replaced with the current code.

The below example creates a procedure ‘employer_details’ which gives the details of the employee.

1> CREATE OR REPLACE PROCEDURE employer_details
2> IS
3> CURSOR emp_cur IS
4> SELECT first_name, last_name, salary FROM emp_tbl;
5> emp_rec emp_cur%rowtype;
6> BEGIN
7> FOR emp_rec in sales_cur
8> LOOP
9> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name
10> || ' ' ||emp_cur.salary);
11> END LOOP;
12>END;
13> /

How to execute a Stored Procedure?

There are two ways to execute a procedure.

1) From the SQL prompt.
EXECUTE [or EXEC] procedure_name;

2) Within another procedure – simply use the procedure name.
procedure_name;


NOTE: In the examples given above, we are using backward slash ‘/’ at the end of the program. This indicates the oracle engine that the PL/SQL program has ended and it can begin processing the statements.

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Explicit Cursors

Explicit Cursors

An explicit cursor is defined in the declaration section of the PL/SQL Block. It is created on a SELECT Statement which returns more than one row. We can provide a suitable name for the cursor.General Syntax for creating a cursor is as given below:

CURSOR cursor_name IS select_statement;

cursor_name – A suitable name for the cursor.
select_statement – A select query which returns multiple rows.

How to use Explicit Cursor?
There are four steps in using an Explicit Cursor.
DECLARE the cursor in the declaration section.
OPEN the cursor in the Execution Section.
FETCH the data from cursor into PL/SQL variables or records in the Execution Section.
CLOSE the cursor in the Execution Section before you end the PL/SQL Block.

1) Declaring a Cursor in the Declaration Section:
DECLARE
CURSOR emp_cur IS
SELECT *
FROM emp_tbl
WHERE salary > 5000;

In the above example we are creating a cursor ‘emp_cur’ on a query which returns the records of all the
employees with salary greater than 5000. Here ‘emp_tbl’ in the table which contains records of all the
employees.

2) Accessing the records in the cursor:
Once the cursor is created in the declaration section we can access the cursor in the execution
section of the PL/SQL program.
How to access an Explicit Cursor?

These are the three steps in accessing the cursor.
1) Open the cursor.
2) Fetch the records in the cursor one at a time.
3) Close the cursor.

General Syntax to open a cursor is:OPEN cursor_name;

General Syntax to fetch records from a cursor is:FETCH cursor_name INTO record_name;

OR
FETCH cursor_name INTO variable_list;

General Syntax to close a cursor is:

CLOSE cursor_name;

When a cursor is opened, the first row becomes the current row. When the data is fetched it is copied to the record or variables and the logical pointer moves to the next row and it becomes the current row. On every fetch statement, the pointer moves to the next row. If you want to fetch after the last row, the program will throw an error. When there is more than one row in a cursor we can use loops along with explicit cursor attributes to fetch all the records.

Points to remember while fetching a row:

· We can fetch the rows in a cursor to a PL/SQL Record or a list of variables created in the PL/SQL Block.
· If you are fetching a cursor to a PL/SQL Record, the record should have the same structure as the cursor.
· If you are fetching a cursor to a list of variables, the variables should be listed in the same order in the fetch statement as the columns are present in the cursor.

General Form of using an explicit cursor is:
DECLARE
variables;
records;
create a cursor;
BEGIN
OPEN cursor;
FETCH cursor;
process the records;
CLOSE cursor;
END;
Explicit Cursor, Lets Look at the example below

Example 1:

1> DECLARE
2> emp_rec emp_tbl%rowtype;
3> CURSOR emp_cur IS
4> SELECT *
5> FROM
6> WHERE salary > 10;
7> BEGIN
8> OPEN emp_cur;
9> FETCH emp_cur INTO emp_rec;
10> dbms_output.put_line (emp_rec.first_name || ' ' || emp_rec.last_name);
11> CLOSE emp_cur;
12> END;

In the above example, first we are creating a record ‘emp_rec’ of the same structure as of table ‘emp_tbl’ in line no 2. We can also create a record with a cursor by replacing the table name with the cursor name. Second, we are declaring a cursor ‘emp_cur’ from a select query in line no 3 - 6. Third, we are opening the cursor in the execution section in line no 8. Fourth, we are fetching the cursor to the record in line no 9. Fifth, we are displaying the first_name and last_name of the employee in the record emp_rec in line no 10. Sixth, we are closing the cursor in line no 11.
What are Explicit Cursor Attributes?

Oracle provides some attributes known as Explicit Cursor Attributes to control the data processing while using cursors. We use these attributes to avoid errors while accessing cursors through OPEN, FETCH and CLOSE Statements.
When does an error occur while accessing an explicit cursor?

a) When we try to open a cursor which is not closed in the previous operation.
b) When we try to fetch a cursor after the last operation.

These are the attributes available to check the status of an explicit cursor.

Attributes	Return values	Example
%FOUND	TRUE, if fetch statement returns at least one row.	Cursor_name%FOUND
	FALSE, if fetch statement doesn’t return a row.
%NOTFOUND	TRUE, , if fetch statement doesn’t return a row.	Cursor_name%NOTFOUND
	FALSE, if fetch statement returns at least one row.
%ROWCOUNT	The number of rows fetched by the fetch statement	Cursor_name%ROWCOUNT
	If no row is returned, the PL/SQL statement returns an error.
%ISOPEN	TRUE, if the cursor is already open in the program	Cursor_name%ISNAME
	FALSE, if the cursor is not opened in the program.

Using Loops with Explicit Cursors:

Oracle provides three types of cursors namely SIMPLE LOOP, WHILE LOOP and FOR LOOP. These loops can be used to process multiple rows in the cursor. Here I will modify the same example for each loops to explain how to use loops with cursors.

Cursor with a Simple Loop:

1> DECLARE
2> CURSOR emp_cur IS
3> SELECT first_name, last_name, salary FROM emp_tbl;
4> emp_rec emp_cur%rowtype;
5> BEGIN
6> IF NOT sales_cur%ISOPEN THEN
7> OPEN sales_cur;
8> END IF;
9> LOOP
10> FETCH emp_cur INTO emp_rec;
11> EXIT WHEN emp_cur%NOTFOUND;
12> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name
13> || ' ' ||emp_cur.salary);
14> END LOOP;
15> END;
16> /

In the above example we are using two cursor attributes %ISOPEN and %NOTFOUND.
In line no 6, we are using the cursor attribute %ISOPEN to check if the cursor is open, if the condition is true the program does not open the cursor again, it directly moves to line no 9.
In line no 11, we are using the cursor attribute %NOTFOUND to check whether the fetch returned any row. If there is no rows found the program would exit, a condition which exists when you fetch the cursor after the last row, if there is a row found the program continues.

We can use %FOUND in place of %NOTFOUND and vice versa. If we do so, we need to reverse the logic of the program. So use these attributes in appropriate instances.
Cursor with a While Loop:

Lets modify the above program to use while loop.

1> DECLARE 

2> CURSOR emp_cur IS
3> SELECT first_name, last_name, salary FROM emp_tbl;
4> emp_rec emp_cur%rowtype;
5> BEGIN
6> IF NOT sales_cur%ISOPEN THEN
7> OPEN sales_cur;
8> END IF;
9> FETCH sales_cur INTO sales_rec;
10> WHILE sales_cur%FOUND THEN
11> LOOP
12> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name
13> || ' ' ||emp_cur.salary);
15> FETCH sales_cur INTO sales_rec;
16> END LOOP;
17> END;
18> /
In the above example, in line no 10 we are using %FOUND to evaluate if the first fetch statement in line no 9 returned a row, if true the program moves into the while loop. In the loop we use fetch statement again (line no 15) to process the next row. If the fetch statement is not executed once before the while loop the while condition will return false in the first instance and the while loop is skipped. In the loop, before fetching the record again, always process the record retrieved by the first fetch statement, else you will skip the first row.
Cursor with a FOR Loop:

When using FOR LOOP you need not declare a record or variables to store the cursor values, need not open, fetch and close the cursor. These functions are accomplished by the FOR LOOP automatically.

General Syntax for using FOR LOOP:FOR record_name IN cusror_name
LOOP
process the row...
END LOOP;

Let’s use the above example to learn how to use for loops in cursors.

1> DECLARE
2> CURSOR emp_cur IS
3> SELECT first_name, last_name, salary FROM emp_tbl;
4> emp_rec emp_cur%rowtype;
5> BEGIN
6> FOR emp_rec in sales_cur
7> LOOP
8> dbms_output.put_line(emp_cur.first_name || ' ' ||emp_cur.last_name
9> || ' ' ||emp_cur.salary);
10> END LOOP;
11>END;
12> /

In the above example, when the FOR loop is processed a record ‘emp_rec’of structure ‘emp_cur’ gets created, the cursor is opened, the rows are fetched to the record ‘emp_rec’ and the cursor is closed after the last row is processed. By using FOR Loop in your program, you can reduce the number of lines in the program.

NOTE: In the examples given above, we are using backward slash ‘/’ at the end of the program. This indicates the oracle engine that the PL/SQL program has ended and it can begin processing the statements.

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Cursors In Pl/Sql

Cursors In Pl/Sql What are Cursors? A cursor is a temporary work area created in the system memory when a SQL statement is executed. A cursor contains information on a select statement and the rows of data accessed by it. This temporary work area is used to store the data retrieved from the database, and manipulate this data. A cursor can hold more than one row, but can process only one row at a time. The set of rows the cursor holds is called the active set. There are two types of cursors in PL/SQL: Implicit cursors These are created by default when DML statements like, INSERT, UPDATE, and DELETE statements are executed. They are also created when a SELECT statement that returns just one row is executed.  Explicit cursors They must be created when you are executing a SELECT statement that returns more than one row. Even though the cursor stores multiple records, only one record can be processed at a time, which is called as current row. When you fetch a row the current row position moves to next row. Both implicit and explicit cursors have the same functionality, but they differ in the way they are accessed.

Implicit Cursors: Application

When you execute DML statements like DELETE, INSERT, UPDATE and SELECT statements, implicit statements are created to process these statements.

Oracle provides few attributes called as implicit cursor attributes to check the status of DML operations. The cursor attributes available are %FOUND, %NOTFOUND, %ROWCOUNT, and %ISOPEN. 

For example, When you execute INSERT, UPDATE, or DELETE statements the cursor attributes tell us whether any rows are affected and how many have been affected.
When a SELECT... INTO statement is executed in a PL/SQL Block, implicit cursor attributes can be used to find out whether any row has been returned by the SELECT statement. PL/SQL returns an error when no data is selected.

The status of the cursor for each of these attributes are defined in the below table. 

Attributes	Return Value	Example
%FOUND	The return value is TRUE, if the DML statements like INSERT, DELETE and UPDATE affect at least one row and if SELECT ….INTO statement return at least one row.	SQL%FOUND
	The return value is FALSE, if DML statements like INSERT, DELETE and UPDATE do not affect row and if SELECT….INTO statement do not return a row.
%NOTFOUND	The return value is FALSE, if DML statements like INSERT, DELETE and UPDATE at least one row and if SELECT ….INTO statement return at least one row.	SQL%NOTFOUND
	The return value is TRUE, if a DML statement like INSERT, DELETE and UPDATE do not affect even one row and if SELECT ….INTO statement does not return a row.
%ROWCOUNT	Return the number of rows affected by the DML operations INSERT, DELETE, UPDATE, SELECT	SQL%ROWCOUNT

For Example: Consider the PL/SQL Block that uses implicit cursor attributes as shown below:

DECLARE  var_rows number(5);

BEGIN

  UPDATE employee 

  SET salary = salary + 1000;

  IF SQL%NOTFOUND THEN

    dbms_output.put_line('None of the salaries where updated');

  ELSIF SQL%FOUND THEN

    var_rows := SQL%ROWCOUNT;

    dbms_output.put_line('Salaries for ' || var_rows || 'employees are updated');

  END IF; 

END; 

In the above PL/SQL Block, the salaries of all the employees in the ‘employee’ table are updated. If none of the employee’s salary are updated we get a message 'None of the salaries where updated'. Else we get a message like for example, 'Salaries for 1000 employees are updated' if there are 1000 rows in ‘employee’ table. 

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Iterative Statements in PL/SQL

Iterative Statements in PL/SQL

Iterative control Statements are used when we want to repeat the execution of one or more statements for specified number of times.

There are three types of loops in PL/SQL:

• Simple Loop
• While Loop
• For Loop


1) Simple Loop

A Simple Loop is used when a set of statements is to be executed at least once before the loop terminates. An EXIT condition must be specified in the loop, otherwise the loop will get into an infinite number of iterations. When the EXIT condition is satisfied the process exits from the loop.

General Syntax to write a Simple Loop is

:LOOP
statements;
EXIT;
{or EXIT WHEN condition;}
END LOOP;


These are the important steps to be followed while using Simple Loop.

1) Initialise a variable before the loop body.
2) Increment the variable in the loop.
3) Use a EXIT WHEN statement to exit from the Loop. If you use a EXIT statement without WHEN condition, the statements in the loop is executed only once.

2) While Loop

A WHILE LOOP is used when a set of statements has to be executed as long as a condition is true. The condition is evaluated at the beginning of each iteration. The iteration continues until the condition becomes false.

The General Syntax to write a WHILE LOOP is:

WHILE <condition>
LOOP statements;
END LOOP;


Important steps to follow when executing a while loop:

1) Initialise a variable before the loop body.
2) Increment the variable in the loop.
3) EXIT WHEN statement and EXIT statements can be used in while loops but it's not done oftenly.

3) FOR Loop

A FOR LOOP is used to execute a set of statements for a predetermined number of times. Iteration occurs between the start and end integer values given. The counter is always incremented by 1. The loop exits when the counter reachs the value of the end integer.

The General Syntax to write a FOR LOOP is:
FOR counter IN val1..val2
LOOP statements;
END LOOP;
val1 - Start integer value.
val2 - End integer value.

Important steps to follow when executing a while loop:

1) The counter variable is implicitly declared in the declaration section, so it's not necessary to declare it explicity.
2) The counter variable is incremented by 1 and does not need to be incremented explicitly.
3) EXIT WHEN statement and EXIT statements can be used in FOR loops but it's not done oftenly.

NOTE: The above Loops are explained with a example when dealing with Explicit Cursors.

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Conditional Statements in PL/SQL

Conditional Statements in PL/SQL

As the name implies, PL/SQL supports programming language features like conditional statements, iterative statements.

The programming constructs are similar to how you use in programming languages like Java and C++.

In this section I will provide you syntax of how to use conditional statements in PL/SQL programming.
Conditional Statements in PL/SQL

IF THEN ELSE STATEMENT
1)
IF condition
THEN
statement 1;
ELSE
statement 2;
END IF;

2)
IF condition 1
THEN
statement 1;
statement 2;
ELSIF condtion2 THEN
statement 3;
ELSE
statement 4;
END IF


3)
IF condition 1
THEN
statement 1;
statement 2;
ELSIF condtion2 THEN
statement 3;
ELSE
statement 4;
END IF;

4)
IF condition1 THEN
ELSE
IF condition2 THEN
statement1;
END IF;
ELSIF condition3 THEN
statement2;
END IF;

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PL/SQL Records

PL/SQL Records

What are records?

Records are another type of datatypes which oracle allows to be defined as a placeholder. Records are composite datatypes, which means it is a combination of different scalar datatypes like char, varchar, number etc. Each scalar data types in the record holds a value. A record can be visualized as a row of data. It can contain all the contents of a row.

Declaring a record:

To declare a record, you must first define a composite datatype; then declare a record for that type.

The General Syntax to define a composite datatype is:
TYPE record_type_name IS RECORD
(first_col_name column_datatype,
second_col_name column_datatype, ...);

• record_type_name – it is the name of the composite type you want to define.
• first_col_name, second_col_name, etc.,- it is the names the fields/columns within the record.
• column_datatype defines the scalar datatype of the fields.
• There are different ways you can declare the datatype of the fields. 

1) You can declare the field in the same way as you declare the fieds while creating the table.
2) If a field is based on a column from database table, you can define the field_type as follows:

col_name table_name.column_name%type;

By declaring the field datatype in the above method, the datatype of the column is dynamically applied to the field. This method is useful when you are altering the column specification of the table, because you do not need to change the code again.

NOTE: You can use also %type to declare variables and constants.

The General Syntax to declare a record of a uer-defined datatype is:
record_name record_type_name;

The following code shows how to declare a record called employee_rec based on a user-defined type.

1. DECLARE 
2. TYPE employee_type IS RECORD 
3. (employee_id number(5), 
4. employee_first_name varchar2(25), 
5. employee_last_name employee.last_name%type, 
6. employee_dept employee.dept%type); 
7. employee_salary employee.salary%type;
8. employee_rec employee_type; 

If all the fields of a record are based on the columns of a table, we can declare the record as follows:
record_name table_name%ROWTYPE;

For example, the above declaration of employee_rec can as follows:
DECLARE
employee_rec employee%ROWTYPE;
The advantages of declaring the record as a ROWTYPE are:
1) You do not need to explicitly declare variables for all the columns in a table.
2) If you alter the column specification in the database table, you do not need to update the code.

The disadvantage of declaring the record as a ROWTYPE is:
1) When u create a record as a ROWTYPE, fields will be created for all the columns in the table and memory will be used to create the datatype for all the fields. So use ROWTYPE only when you are using all the columns of the table in the program.

NOTE: When you are creating a record, you are just creating a datatype, similar to creating a variable. You need to assign values to the record to use them.

The following table consolidates the different ways in which you can define and declare a pl/sql record.

Passing Values To and From a Record

When you assign values to a record, you actually assign values to the fields within it.
The General Syntax to assign a value to a column within a record direclty is:
record_name.col_name := value;

If you used %ROWTYPE to declare a record, you can assign values as shown:
record_name.column_name := value;

We can assign values to records using SELECT Statements as shown:
SELECT col1, col2
INTO record_name.col_name1, record_name.col_name2
FROM table_name
[WHERE clause];

If %ROWTYPE is used to declare a record then you can directly assign values to the whole record instead of each columns separately. In this case, you must SELECT all the columns from the table into the record as shown:
SELECT * INTO record_name
FROM table_name
[WHERE clause];
Lets see how we can get values from a record.
The General Syntax to retrieve a value from a specific field into another variable is:
var_name := record_name.col_name;

The following table consolidates the different ways you can assign values to and from a record:

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PL/SQL Constants

PL/SQL Constants

As the name implies a constant is a value used in a PL/SQL Block that remains unchanged throughout the program. A constant is a user-defined literal value. You can declare a constant and use it instead of actual value.

For example: If you want to write a program which will increase the salary of the employees by 25%, you can declare a constant and use it throughout the program. Next time when you want to increase the salary again you can change the value of the constant which will be easier than changing the actual value throughout the program.

General Syntax to declare a constant is:

constant_name CONSTANT datatype := VALUE;

• constant_name is the name of the constant i.e. similar to a variable name.
• The word CONSTANT is a reserved word and ensures that the value does not change.
• VALUE - It is a value which must be assigned to a constant when it is declared. You cannot assign a value later.

For example, to declare salary_increase, you can write code as follows:

DECLARE
salary_increase CONSTANT number (3) := 10; 

You must assign a value to a constant at the time you declare it. If you do not assign a value to a constant while declaring it and try to assign a value in the execution section, you will get a error. If you execute the below Pl/SQL block you will get error.

1. DECLARE 
2. salary_increase CONSTANT number(3); 
3. BEGIN 
4. salary_increase := 100; 
5. dbms_output.put_line (salary_increase); 
6. END;

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PL/SQL Variables

                       

PL/SQL Variables

PL/SQL Placeholders

Placeholders are temporary storage area. Placeholders can be any of Variables, Constants and Records. Oracle defines placeholders to store data temporarily, which are used to manipulate data during the execution of a PL SQL block.

Depending on the kind of data you want to store, you can define placeholders with a name and a datatype. Few of the datatypes used to define placeholders are as given below.

Number (n,m) , Char (n) , Varchar2 (n) , Date , Long , Long raw, Raw, Blob, Clob, Nclob, Bfile

PL/SQL Variables

These are placeholders that store the values that can change through the PL/SQL Block.

General Syntax to declare a variable is

variable_name datatype [NOT NULL := value ];

• variable_name is the name of the variable.
• 
  
• datatype is a valid PL/SQL datatype.
• 
  
• NOT NULL is an optional specification on the variable.
• 
  
• value or DEFAULT valueis also an optional specification, where you can initialize a variable.
• 
  
• Each variable declaration is a separate statement and must be terminated by a semicolon.

For example, if you want to store the current salary of an employee, you can use a variable.

DECLARE
salary number (6);

* “salary” is a variable of datatype number and of length 6.

When a variable is specified as NOT NULL, you must initialize the variable when it is declared.

For example: The below example declares two variables, one of which is a not null.

DECLARE
salary number(4);
dept varchar2(10) NOT NULL := “HR Dept”;
The value of a variable can change in the execution or exception section of the PL/SQL Block. We can assign values to variables in the two ways given below.

1) We can directly assign values to variables.

The General Syntax is:
variable_name:= value;

2) We can assign values to variables directly from the database columns by using a SELECT.. INTO statement. The General Syntax is:

SELECT column_name INTO variable_name
FROM table_name
[WHERE condition];

Example: The below program will get the salary of an employee with id '1116' and display it on the screen.

1. DECLARE 
2. var_salary number(6); 
3. var_emp_id number(6) = 1116; 
4. BEGIN
5. SELECT salary INTO var_salary 
6. FROM employee 
7. WHERE emp_id = var_emp_id; 
8. dbms_output.put_line(var_salary); 
9. dbms_output.put_line('The employee ' || var_emp_id || ' has salary ' || var_salary); 
10. END; 

/

NOTE: The backward slash '/' in the above program indicates to execute the above PL/SQL Block.

Scope of PS/SQL Variables

PL/SQL allows the nesting of Blocks within Blocks i.e, the Execution section of an outer block can contain inner blocks. Therefore, a variable which is accessible to an outer Block is also accessible to all nested inner Blocks. The variables declared in the inner blocks are not accessible to outer blocks. Based on their declaration we can classify variables into two types.

Local variables - These are declared in a inner block and cannot be referenced by outside Blocks.

Global variables - These are declared in a outer block and can be referenced by its itself and by its inner blocks.

For Example: In the below example we are creating two variables in the outer block and assigning thier product to the third variable created in the inner block. The variable 'var_mult' is declared in the inner block, so cannot be accessed in the outer block i.e. it cannot be accessed after line 11. The variables 'var_num1' and 'var_num2' can be accessed anywhere in the block.

1.  DECLARE
2.  var_num1 number; 
3.  var_num2 number; 
4.  BEGIN 
5.  var_num1 := 100; 
6.  var_num2 := 200; 
7.  DECLARE 
8.  var_mult number; 
9.  BEGIN 
10.  var_mult := var_num1 * var_num2; 
11.  END; 
12.  END; 
13.  /

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Advantages of PL/SQL

Advantages of PL/SQL

These are the Advantages of PL/SQL

Block Structures: PL SQL consists of blocks of code, which can be nested within each other. Each block forms a unit of a task or a logical module. PL/SQL Blocks can be stored in the database and reused.

Procedural Language Capability: PL SQL consists of procedural language constructs such as conditional statements (if else statements) and loops like (FOR loops).

Better Performance: PL SQL engine processes multiple SQL statements simultaneously as a single block, thereby reducing network traffic.

Error Handling: PL/SQL handles errors or exceptions effectively during the execution of a PL/SQL program. Once an exception is caught, specific actions can be taken depending upon the type of the exception or it can be displayed to the user with a message.

Ability to work with real time scenario 

Tight integration with SQL

Full Portability

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Oracle Master-Details forms for beginners

Creating a Master/Detail Form

In this section, the basic steps for creating a Master/Detail form are introduced. A Master/Detail form is a form that has two blocks arranged in a master/detail relationship.

The Master/Detail Relationship

The Master/Detail relationship is a common relationship between entities in a business. In an Entity-Relationship diagram, these are shown as “One to Many” relationships. In a physical database design, a single Master record references one or more detail records in another table. A record in the detail table will relate to exactly one master record in the master table. Another name for this relationship is called parent-child. Examples of this relationship include:

1. A Customer Order with many OrderItems.
2. A Department with many Employees.
3. An Employee with many Dependents.
4. A Company with many Branch Offices.
5. A Recipe with many Recipe Steps.
6. An Inventory location with many Inventory Items.

Oracle Forms implements the master/detail relationship using two data blocks. The first block corresponds to the master table and the second block corresponds to the detail table. There are two major functions in a Master/Detail form:

· Oracle Forms coordinates values between the two blocks through a series of form and block level triggers.

· Oracle Forms guarantees that the detail block will display only records that are associated with the current record in the master block.

Note that a Master/Detail form is simply one way of viewing the data in two related tables. Forms do not affect the schema in terms of creating, dropping or enforcing database level referential integrity constraints.

Steps to Create a Master/Detail Form

In this section, a set of step by step instructions for creating a Master/Detail form are given. The form will allow a user to query a given department in the company and then will display all of the employees in that company.

The schema used is the same one suggested in the Prerequisites section at the beginning of this tutorial. Notice that the DNO column in the EMPLOYEE table gets its values from the DNUMBER column in the DEPARTMENT table. In other words, to join the two tables in a query, one might specify a WHERE clause such that: EMPLOYEE.DNO = DEPARTMENT.DNUMBER.

Create the Master Block

In the Object Navigator, click on the Forms branch at the very top. Create a new form by pulling down the File menu and choosing the New menu item. Then choose Form from the flyout menu.

Using the same steps given in the prior section on 6. Creating a Form with a Single Block, create a new block named DEPARTMENT that contains all of the columns in the DEPARTMENT table. Briefly:

1. Pull down the Tools menu and choose the Data Block wizard.

2. Create a data block for a table/view.

3. Specify the DEPARTMENT table and select all of the columns (DNAME, DNUMBER, MGRSSN and MGRSARTDATE).

4. Create the data block and then go on to the Layout wizard.

5. Apply the Department data block to a new canvas.

6. Add all of the columns as Displayed Items.

7. Change the labels to:
Dept. Name
Dept. Number
Mgr. Ssn
Mgr. Start Date

8. Choose a Form layout.

9. Specify a frame title of “Departments” and select only 1 record to be displayed.

10. Save the form as deptemp.fmb and then compile and run it to make sure it is working properly.

11. Use the QBE features to retrieve only those departments with DNUMBER greater than 2. Then, do another QBE query to retrieve only those departments with the letter H in their name (try %H%).

After this first step, the deptemp form should look like the following:

Create the Detail Block

Now that we have the master block DEPARTMENT created, we can now create the detail block EMPLOYEE and associate it with the master block. Perform the following steps:

1. Return to the Object Navigator (pull down the Tools menu and choose Object Navigator).

2. In the Object Navigator, click on the Data Blocks branch of the DEPTEMP form (do not click on the department data block, however).

3. Pull down the Tools menu and choose the Data Block wizard.
Note: If the DEPARTMENT data block (or any of its items) is still selected, activating the Data Block wizard will cause the existing block to be edited instead of creating a new block (which is what is required in this part of the tutorial).

4. Select the EMPLOYEE table and include the FNAME, LNAME, SSN, BDATE, SALARY and DNO columns.

5. Because at least one data block already exists in the form, the next step in the wizard will be to create a relationship between the existing data block (DEPARTMENT in this case) and the new block being created.

The wizard can construct the relationship based on table level constraints it learns from the database schema. For example, in the CREATE TABLE and ALTER TABLE statements given at the start of this tutorial, foreign key constraints were specified between DEPARTMENT and EMPLOYEE, and between EMPLOYEE and DEPENDENT. However, such relationships are not always implemented in table level constraints.
The developer can also specify the relationship manually. In this case, the relationship will be specified manually.

De-select the Auto-join data blocks option.
Click on the Create Relationship button to list the available data blocks.
In the next dialog box Relation Type, choose Based on a join condition and click the OK button.

When the list of blocks appears, choose the DEPARTMENT data block.
Arrange the Detail Item (DNO) and Master Item (DNUMBER) such as that the join condition becomes: EMPLOYEE.DNO = DEPARTMENT.DNUMBER

6. Name the data block EMPLOYEE.

7. Create the data block and then call the Layout wizard.

8. Be sure to choose the existing canvas (CANVAS4 in this example) and include all of the items except the DNO as displayed.
The DNO column (item) will still be a part of the EMPLOYEE data block, however, it will not be displayed to the user.

9. Touch up the labels for the fields and choose the Tabular layout.

10. Give the Frame Title as “Employees” and select 5 Records displayed with 0 distance between records.

11. Save the form (it should already have the name deptemp.fmb) and then compile and run it. Note that after compilation, any errors encountered will be displayed.

The following figure shows the master/detail form running:

Notice that by scrolling the master block DEPARTMENT to a new department number (using the up and down arrow keys), the employees for that department are automatically queried and displayed.

To navigate between the Master and Detail blocks, use:

· To go to the next block: Press CTRL-PageDown or pull down the Block menu and choose Next

· To go to the previous block: Press CTRL-PageUp or pull down the Block menu and choose Previous

 Relation Properties of a Master/Detail Form

There are a number of properties in a master/detail form that can be changed to suit particular behavior of the form. In the figure below, the Object Navigator has several new objects on it including Relations.

To view the properties for the DEPARTMENT_EMPLOYEE relation, open up the DEPARTMENT block and then open the Relations block by clicking on the + symbols. Then click on the DEPARTMENT_EMPLOYEE relation with the right mouse button and select Properties.

There are several interesting properties in the relations property sheet:

1. Name – The name of the Relation. This is typically made up of the names of the blocks.

2. Relation Type – The type of the relation: Join or Ref.
A Join relation uses the typical SQL join (in the Where clause) to bring the two tables (data blocks) together. The Ref relation type is used for abstract data types and object references.

 3. Detail Data Block – The name of the detail data block specified when the detail data block was created.

 4. Join Condition – This is the join condition in effect for queries to the database. This was specified when the detail data block was created.

 5. Delete Record Behavior – Used to specify how the deletion of a record in the master block affects records in the detail block. It supports the following settings:

o Non-isolated: Prevents the deletion of a master record if associated detail records exist in the database.

o Isolated: Deleting the master record will not affect the associated detail records in the database.

o Cascading: Deletes the master record and automatically deletes any associated detail records.

6. Coordination – Deferred – Indicates when detail records should be queried when a master record is queried.

o Yes: Form does not query the detail records until the user navigates to the detail block.

o No: Detail records are fetched immediately when a user queries the master record.

Deferred is sometimes set to Yes in cases where there are a lot of detail records for each master record. In such cases, a lot of data must be queried and delivered to the client each time a new record is displayed in the master block. When Deferred is set to Yes, the user can scroll down to the master record of interest and then navigate to the detail block (CTRL-PageDown) to query the related detail records.

7. Coordination – Auto-query – Applied to deferred queries only

o Yes: the query is automatically executed when the user navigates to the detail block.

o No: the query must be executed manually by the user after they navigate to the detail block.

8. Prevent Masterless operation – Specifies whether users are allowed to query or insert records in a detail block when no master record is in place.

o Yes: Users may not query or insert when no master record is in place.

o No: Users may query or insert when no master record is in place.

These settings are used to “tune” the overall performance of a master/detail form. As mentioned above, in cases where a large number of detail records are associated with each master record, it is a good idea to set coordination-Deferred to Yes to avoid unnecessary transfers of data between the server and client. This will also speed up the display of master records as the user can freely scroll through them without a pause to query and deliver the detail records.

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Oracle report for beginners

Create a report using wizard in Report Builder.

Open Report Builder


This is the first screen you will see. Select the first option “Use the Report Wizard” and click OK.



Click Next


Enter Report Title: erpschools_sample_report and then select “Tabular” option.

As per name “Tabular” our output will be organized in a tabular way (rows and columns).

You can select any option you want based on your requirement/wish.

Then click NEXT



Select the first option “SQL statement” and click Next

SQL statement: If you select this option you have to write the query directly.

Express Query: If you select this option you have to connect to the database and then select the tables/columns you want to display in the report. Simply this is wizard for building the query.



Enter the below SQL Query and then click Next

SELECT * FROM MTL_SYSTEM_ITEMS_B WHERE SEGMENT1 =:P_SEGMENT1

In the above query: p_segment1 is called as bind parameter/variable.

Note: There are two types of parameters that we use in reports. Lexical Parameter and Bind Parameter

Bind Parameter: This is used to pass the values dynamically at run time.

Examples: 1) If you want to see only one item from your inventory and you want to select that item at the time of running report. 2) If you want select only particular department employees and you want to select that department at runtime.

Lexical Parameter: This parameter is used to build the query dynamically.

Examples: If you have two users A, B will be running the report and if use A want to see only columns 1, 2, 3 where as User B want to see columns 2, 3, 4 in that case we build the query dynamically using lexical parameters.



Here you have to enter the username, password of your database. Usually in many development environments username and password will be “apps”.


So enter apps/apps@datbase and click Connect


Once you are successfully connected you will see the above message box.


Action: Click OK to Proceed


Based on your Query above screen will display the Available Fields. In this case we will have all columns from mtl_system_items_b table. Select the columns you want to display in the report and use arrow buttons to move them to Displayed Fields.



Here I have selected the three columns. You have to select the SEMENT1 column if you have any parameters associated with it, as we have one parameter with it I am selecting that field.


click Next


In the above screen you have option to select any Totals/Sum/Averages if you want. Here i will proceed without selecting any.


Click Next


In this screen you have the option to change the heading/display column names in the report. Here i have changed the “Description” to “Item Description” and “SEGMENT1″ to “Item Number”.


click Next


Here you have the option to select any template if you have. I will go with “No Template” option


click Next



Finally click Finish



It will prompt you with the “P Segment1″ parameter. Enter some valid value and click green signal button to run the report.

Note: To check valid parameters for this report run the below query and copy the output.

SELECT SEGMEN1 FROM MTL_SYSTEM_ITEMS_B WHERE ROWNUM<2;




Finally this is my report output.


Click File — Save and enter your report name (sample_report.rdf to use concurrent program registration document for your reference)

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