Application of crosstab in SQL Server

In the actual development process of the project , We sometimes encounter the problem of crosstab ,  for instance . Let's say there's a table T_ENT_EXHIBITION_SEATS ,  The structure and demonstration data are as follows ：

 

ENT_NAME	EXHIBITION_NAME	EXHIBITION_SEATS
ENTA	105-1	5
ENTA	105-2	7
ENTA	106-1	13
ENTB	105-2	2
ENTC	105-1	18
ENTC	106-2	7
ENTD	105-2	16
ENTE	106-1	3

 

According to the above data sheet and data , We need to get EXHIBITION_NAME Data of becomes a column , Get the following structure and data ：

 

ENT_NAME	105-1	105-2	106-1	106-2
ENTA	5	7	13	0
ENTB	0	2	0	0
ENTC	18	0	0	7
ENTD	0	16	0	0
ENTE	0	0	3	0

 

stay SQL Server in , According to different versions , We can have different solutions , With SQL Server 2005 As a watershed , Let's start with SQL Server 2000 How to solve this problem . Usually we say that the data column generated by the crosstab ( image EXHIBITION_NAME)  It can be data with a certain range unchanged , There is also dynamic data that can be maintained , The columns generated by the former are fixed , The latter can change with the increase or decrease of maintenance data , Different situations are handled differently , Solve the former first , Relatively simple , We can use CASE Statement to complete ：

SELECT ENT_NAME,

       ISNULL(CASE WHEN EXHIBITION_NAME = '105-1'

            THEN EXHIBITION_SEATS

       END, 0) AS EXHIBITION_NAME,

       ISNULL(CASE WHEN EXHIBITION_NAME = '105-2'

            THEN EXHIBITION_SEATS

       END, 0) AS EXHIBITION_NAME,

       ISNULL(CASE WHEN EXHIBITION_NAME = '106-1'

            THEN EXHIBITION_SEATS

       END, 0) AS EXHIBITION_NAME,

       ISNULL(CASE WHEN EXHIBITION_NAME = '106-2'

            THEN EXHIBITION_SEATS

       END, 0) AS EXHIBITION_NAME

FROM T_ENT_EXHIBITION_SEATS

ORDER BY ENT_NAME ASC   

If the data column is changing , Then we need to use dynamic SQL Here we go ：    

DECLARE @DynamicPIVOT NVARCHAR(4000)

 

SELECT @DynamicPIVOT = 'SELECT ENT_NAME'

 

SELECT @DynamicPIVOT = @DynamicPIVOT +

                       ', ISNULL(SUM(CASE WHEN EXHIBITION_NAME = ''' + EXHIBITION_NAME +

                       ''' THEN EXHIBITION_SEATS END), 0) AS ''' + EXHIBITION_NAME + ''''

FROM T_ENT_EXHIBITION_SEATS

GROUP BY EXHIBITION_NAME

ORDER BY EXHIBITION_NAME ASC

 

SET @DynamicPIVOT = @DynamicPIVOT + ' FROM T_ENT_EXHIBITION_SEATS GROUP BY ENT_NAME '

 

EXECUTE(@DynamicPIVOT)

here we are SQL Server 2005 perhaps SQL Server 2008, Microsoft has provided us with PIVOT To get the job done , Especially in the case of fixed data columns , Especially simple ：

SELECT ENT_NAME,

       ISNULL([105-1], 0) AS [105-1],

       ISNULL([105-2], 0) AS [105-2],

       ISNULL([106-1], 0) AS [106-1],

       ISNULL([106-2], 0) AS [106-2]

FROM T_ENT_EXHIBITION_SEATS

PIVOT (

 SUM(EXHIBITION_SEATS)

 FOR EXHIBITION_NAME IN ([105-1], [105-2], [106-1], [106-2])

) AS PVT

ORDER BY ENT_NAME;

It should be noted that , The data column of the query must be the same as IN Clear scope corresponds to （ The order is irrelevant ）. as for , Dynamic data columns , Still dynamic SQL To complete . How to write , I don't want to go into it .

About PIVOT You can refer to the following links for the use of ：

http://technet.microsoft.com/en-us/library/ms177410(SQL.90).aspx