SQL SERVER | Conditional Statements

While loop: In SQL SERVER, while loop can be used in similar manner as any other programming language. A while loop will check the condition first and then execute the block of SQL Statements within it as long as the condition evaluates true. 

Syntax:

WHILE condition
BEGIN
   {...statements...}
END;

Parameters: 
1. Condition: The condition is tested in each pass through the loop. If condition evaluates to TRUE, the loop body is executed otherwise the loop is terminated. 
2. Statements: The statements that needs to be executed in each pass through the loop. 


Example: 
 

Output: 
 

Break statement: BREAK statement as the name signifies is used to break the flow of control. It can be used in SQL in similar manner as any other programming language. 


Example: While loop with Break statement 

 

Output: 
 

Note : In the example, when variables value became five, BREAK Statement is executed and the control gets out from the Loop. 

Do-While loop: SQL server does not have the feature of do-while loop but by doing little modifications in while loop, the same behaviour can be achieved. 


Example 1: 
 

Output: 
 

Example 2: 
 

Output: 
 

CASE statement: In SQL Server, the CASE statement has the same functionality as IF-THEN-ELSE statement. 

Syntax: 
 

CASE Expression
   WHEN Con_1 THEN Output1 
   WHEN Con_2 THEN Output2
   WHEN Con_3 THEN Output3
   WHEN Con_4 THEN Output4
   ...
   WHEN Con_n THEN Outputn
   ELSE output
END

Parameters: 
1. Expression: The value to be compared to the list of conditions(Optional). 
2. Con_1, Con_2, ...Con_n: The conditions are required and are evaluated in the order they are listed. Once a condition is true, the CASE function will return the result and not evaluate the conditions any further. 
3. Output1, Output2, ...Outputn: The output to be printed once the condition evaluates true. 

Example: 
 

Output: