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Define a PL/SQL sample block. -Database management System

Presidency University, Bangalore - Database management system questions

Asked On2017-07-06 05:40:20 by:Aparna-Dasgupta

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PL/SQL is block structured language divided into three logical blocks.
BEGIN block and END; keyword are compulsory, and other two block DECLARE and EXCEPTION are optional block. END; is not a block only keyword to end of PL/SQL program.
PL/SQL block structure follows divide-and-conquer approach to solve the problem stepwise.
Variables and constants are declared, initialized within this section.
Variables and Constants : In this block, declare and initialize variables (and constants). You must have to declare variables and constants in declarative block before referencing them in procedural statement.
Declare Variables and Assigning values : You can define variable name, data type of a variable and its size. Date type can be: CHAR, VARCHAR2, DATE, NUMBER, INT or any other.
1.DECLARE   -- DECLARE block, declare and initialize values
2. designation VARCHAR2(30);
3 eno number(5) := 5;
4. id BOOLEAN;
6.BEGIN   -- BEGIN block, also assign values  
7. designation := UPPER('Web Developer');
8. id := TRUE;
9. inter := INTERVAL '45' YEAR; 
Declare Constants and Assigning values : Constants are declared same as variable but you have to add the CONSTANT keyword before defining data type. Once you define a constant value you can't change the vaue.
1.designation CONSTANT VARCHAR2(30) := 'Web Developer';
BEGIN block is procedural statement block which will implement the actual programming logic. This section contains conditional statements (if...else), looping statements (for, while) and Branching Statements (goto) etc.

PL/SQL easily detects user defined or predefined error condition. PL/SQL is famous for handling errors in smart way by giving suitable user friendly messages. Errors can be rise due to wrong syntax, bad logical or not passing a validation rules.
You can also define exception in your declarative block and later you can execute it by RAISE statement.
2 check_exist EXCEPTION; -- declare exception type
3 ...
5. ....
6. RAISE check_exist;  -- Raise exception
7. ....
9.WHEN check_exist THEN  -- execute raise exception
10. ..... 
Note :
1.BEGIN block and END; keyword are compulsory of any PL/SQL program.
2.Where as DECLARE and EXCEPTION block are optional.

Answerd on:2017-07-09 Answerd By:prajwalamv

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