SQL Condition in SELECT Query

Sometimes we need to check some condition in SQL SELECT query. Today I am going to show you the way of this by en example.
Let we have a table as follow:

Let we have to show a table where credit and debit will be summed and there will be two more row named CREDITFINAL and DEBITFINAL.
Let,

• sum of Credit for Head X is CX
• sum of Debit for Head X is DX

Now

• CREDITFINAL will contain the data if CX>DX with value CX-DX
• DEBITFINAL will contain the data if DX>=CX with value DX-CX

To show data such way we need to check condition in SQL SELECT statement. Now I am going to perform this task step by step so that you will understand easily.

First Let show only the column HeadID, HeadName, Credit & Debit. For this our query will be as follow:-

SELECT [HeadID] 
      ,[HeadName] 
      ,[Date] 
      ,[Credit] 
      ,[Debit] 
FROM [sql_condition]

Output will be as follow:

Now Let we will show the data by summing the CREDIT and DEBIT of same type, means same HeadID and HeadName.

Output will be as follow:-

Here sum of CREDIT for any Head will be show in column name CREDITSUM, because I use AS.


Now I am going to perform my main task.

• CREDITFINAL will contain the data if   CX>DX   with value CX-DX
• DEBITFINAL    will contain the data if   DX>=CX  with value DX-CX

Here I am going to USE CAST, you can find more help, Click Here.

Syntax for CAST:

CAST ( expression AS data_type [ ( length ) ] )

For perform condition here I am going to use CASE, which syntax is given bellow

CASE expression 
     WHEN expression1 THEN result_expression1 
     WHEN when_expression2 THEN result_expression2

     ................... 

     [ ELSE else_result_expression ] 

END 

Searched CASE expression:
CASE
     WHEN Boolean_expression THEN result_expression [ ...n ] 
     [ ELSE else_result_expression ] 
END

And My query is as follow for the final task.

And the output is as follow

Any kind of advice is appreciated.
Thanks.