Applied SQL…

In this article we will be taking a look at the new analytical function FIRST_VALUE  in SQL Server 2012. Let us understand them with examples.

This function returns the first value from an ordered set of values. The syntax for the same is

FIRST_VALUE ( [scalar_expression ] )
OVER ( [ partition_by_clause ]
order_by_clause [ rows_range_clause ] )

Let us create a sample table and understand this on SQL Server 2012. The following script does the same. Lets observe the output of the script below

CREATE TABLE [dbo].[MyFirstLastVaL](
[id] [int] IDENTITY(1,1) NOT NULL,
[Name] [nchar](10) NOT NULL,
[MarksInMaths] [int] NOT NULL )
GO
insert into MyFirstLastVaL values('Alan',99)
insert into MyFirstLastVaL values('Brent',29)
insert into MyFirstLastVaL values('Charlie',25)
insert into MyFirstLastVaL values('David',37)
insert into MyFirstLastVaL values('Ello',15)
insert into MyFirstLastVaL values('Frank',59)
insert into MyFirstLastVaL values('Grant',16)
insert into MyFirstLastVaL values('Honey',18)
insert into MyFirstLastVaL values('Irene',86)
insert into MyFirstLastVaL values('Jack',76)
insert into MyFirstLastVaL values('Kalou',66)
insert into MyFirstLastVaL values('Lisa',68)
insert into MyFirstLastVaL values('Mike',98)
insert into MyFirstLastVaL values('Lisa',28)
insert into MyFirstLastVaL values('Mike',45)
insert into MyFirstLastVaL values('Alan',19)
insert into MyFirstLastVaL values('Brent',92)
insert into MyFirstLastVaL values('Charlie',35)
insert into MyFirstLastVaL values('Irene',36)
insert into MyFirstLastVaL values('Jack',67)
insert into MyFirstLastVaL values('Kalou',96)

SELECT id,name,MarksInMaths,
FIRST_VALUE(marksinmaths) OVER (ORDER BY marksinmaths) MyFirstVal
FROM MyFirstLastVaL

Now let us use the function with partition by clause and observe the output

SELECT id,name,MarksInMaths,FIRST_VALUE(MarksInMaths)
OVER (PARTITION BY Name ORDER BY MarksInMaths) MyFirstVal
FROM MyFirstLastVaL

In the first case the query simply returns the first value of the entire data set whereas in the second case the output is based on the marksinmaths column, so the FIRST_VALUE is different but the same for each partition.