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NULLIF function in SQL Server

This article will show you in detail how to use the NULLIF function handler in SQL Server with specific syntax and examples to better visualize and capture functions.

Describe

The NULLIF function in SQL Server compares two expressions to be passed. If the first expression is equal to the second expression, NULLIF will return NULL. Otherwise, the function will return the first expression, expression 1.

Syntax

To use the NULLIF statement in SQL Server, we use the following syntax:

 NULLIF(bieuthuc1, bieuthuc2)

Parameters :

  1. bieuthuc1, bieuthuc2: expressions to compare. The values ​​in the expression must belong to the same data type.

Note :

  1. NULLIF function can be used in later versions of SQL Server: SQL Server 2017, SQL Server 2016, SQL Server 2014, SQL Server 2012, SQL Server 2008 R2, SQL Server 2008, and SQL Server 2005.

For example

See how to use the NULLIF statement in SQL Server.

 SELECT NULLIF('TipsMake.com', 'TipsMake.com'); 
 Result: NULL (trả về NULL vì các giá trị bằng nhau) 
 
 SELECT NULLIF('TipsMake.com', 'QuanTriMang'); 
 Result: 'TipsMake.com' (trả về giá trị đầu tiên vì các giá trị khác nhau) 
 
 SELECT NULLIF(12, 12); 
 Result: NULL (trả về NULL vì các giá trị bằng nhau) 
 
 SELECT NULLIF(12, 45); 
 Result: 12 (trả về giá trị đầu tiên vì các giá trị khác nhau) 
 
 SELECT NULLIF('2019-05-01', '2019-05-01'); 
 Result: NULL (trả về NULL vì các giá trị bằng nhau) 
 
 SELECT NULLIF('2019-05-01', '2019-04-30'); 
 Result: '2019-05-01' (trả về giá trị đầu tiên vì các giá trị khác nhau)

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