Skip to main content

Difference between null and coalesce

ISNULL

  1. ISNULL function is used to replace the NULL value with specified value.
  2. It contains only two arguments.
  3. Same data type not compulsory.

Example -1:

SELECT ISNULL(NULL,'Raki') AS [ISNULL]

Output: Raki

Example -2:

DECLARE @name VARCHAR(10)
DECLARE @marks INT =500
SELECT ISNULL(@name,@marks) AS [ISNULL]

Output: 500

Example-3:

SELECT ISNULL(NULL,NULL,'Raki') AS [ISNULL]     

Output:

  Msg 174, Level 15, State 1,
  The isnull function requires 2 argument(s).

COALESCE

  1. Coalesce function is returns first non null value among arguments.  
  2. It contains multiple arguments.
  3. Same data type compulsory for arguments or precedence data type order should follow.


Example-1:

SELECT COALESCE(NULL,NULL,'Raki') as [COALESCE]

Output: Raki

Example-2:

DECLARE @name VARCHAR(5)='Raki'
DECLARE @marks INT =500
SELECT COALESCE(@name,@marks) as [COALESCE]

Output:  
Msg 245, Level 16, State 1, Line 3
Conversion failed when converting the varchar value 'Raki' to data type int.


         



Labels:

Comments

Post a Comment

Popular posts from this blog

How to Use Merge Statement Using XML Data

We now that merge statement in SQL SERVER. With Merge statement we can merge the data from Source table into Target table. In the Last article we have already seen about Merge Statement .   These articles we will work around merge statement over xml data type. We know that xml data type SQL SERVER. XML Data type is used to storing xml data used Bulk Insert Data into SQL Tables. Example: --Create Student Table if object_id ( 'Student' ) is null create table Student ( id int identity ( 1 , 1 ) , Name varchar ( 20 ), Marks int ) Declare Xml Data Type and Assign Some Xml Data. Declare @Data xml set @Data = '<Root> <Student> <Name>Rakesh</Name> <Marks>80</Marks> </Student> <Student> <Name>Mahesh</Name> <Marks>90</Marks> </Student> <Student> <Name>Gowtham</Name...
Post a Comment
Read more

SP_MSForeachtable

Some times we need to query on the all the tables in one data base single statement. We use SP_MSForeachtable this is known as undocumented stored procedures . These all are system stored procedures. These stored procedures is place in Master database. NOTE: Please do not run all these queries in Production environment Example: create database UnDocumentedStoredProcedure use UnDocumentedStoredProcedure create table Emp ( ID int identity ( 1 , 1 ), Name varchar ( 50 ), Salary int ) insert into Emp ( Name , Salary ) values ( 'rakesh' , 8000 ),( 'raju' , 9000 ) create table Dept ( ID int identity ( 1 , 1 ), DeptName varchar ( 100 ) ) insert into Dept ( DeptName ) values ( 'CSE' ),( 'IT' ) We are created new database and also created some table with some dummy data. Select all tables data: exec sp_MSForeachtable 'select * from ?...
1 comment
Read more