Friday, 21 February 2014

SQL Script to drop and re-create all foreign keys in SQL server

I had to load some database with fresh data every few days for testing purpose and some reporting purpose. I have a SSIS package to load the data from source database but one issue I faced is I could not truncate the tables because of foreign keys. So Initially I started with using DELETE, but which was taking some time. So to improve the performance and get rid of all foreign key before start of the load and then re-create them after load is finish, I have written one interesting script as below. This script give DROP and CREATE statement for all foreign key which I was running in my package.

WITH RefColumns AS

(

       SELECT

              C.referenced_object_id AS [object_id],

              C.parent_object_id,

              STUFF((SELECT ', ' + QUOTENAME(B.name)

                     FROM sys.foreign_key_columns A 

                           JOIN sys.columns B ON B.[object_id] = A.referenced_object_id AND B.column_id = A.referenced_column_id

                           WHERE C.parent_object_id = A.parent_object_id AND C.referenced_object_id = A.referenced_object_id

                           FOR XML PATH('')), 1, 2, '') AS ColumnNames

       FROM sys.foreign_key_columns C

       GROUP BY C.referenced_object_id, C.parent_object_id

)

,ParentColumns AS

(

       SELECT

              C.parent_object_id AS [object_id],

              C.referenced_object_id,

              STUFF((SELECT ', ' + QUOTENAME(B.name)

                     FROM sys.foreign_key_columns A 

                           JOIN sys.columns B ON B.[object_id] = A.parent_object_id AND B.column_id = A.parent_column_id

                           WHERE C.parent_object_id = A.parent_object_id AND C.referenced_object_id = A.referenced_object_id

                           FOR XML PATH('')), 1, 2, '') AS ColumnNames

       FROM sys.foreign_key_columns C

       GROUP BY C.parent_object_id, C.referenced_object_id

)

 

SELECT

       'ALTER TABLE ' + QUOTENAME(SCHEMA_NAME(PT.[schema_id])) + '.' + QUOTENAME(PT.name) + ' DROP  CONSTRAINT' + ' ' + QUOTENAME(FK.name) AS [DropFKScript],

       'ALTER TABLE ' + QUOTENAME(SCHEMA_NAME(PT.[schema_id])) + '.' + QUOTENAME(PT.name) + ' WITH CHECK ADD  CONSTRAINT '+ QUOTENAME(FK.name) + CHAR(13) + CHAR(10) +

       'FOREIGN KEY(' + PC.ColumnNames + ')' + CHAR(13) + CHAR(10) +

       'REFERENCES ' + QUOTENAME(SCHEMA_NAME(RT.[schema_id])) + '.' + QUOTENAME(RT.name) + ' (' + RC.ColumnNames + ')' + CHAR(13) + CHAR(10) + 'GO' + CHAR(13) + CHAR(10) +

       'ALTER TABLE ' + QUOTENAME(SCHEMA_NAME(PT.[schema_id])) + '.' + QUOTENAME(PT.name) + ' CHECK CONSTRAINT ' + QUOTENAME(FK.name) + CHAR(13) + CHAR(10) + 'GO' + CHAR(13) + CHAR(10)

       AS [CreateFKScript]

FROM sys.foreign_keys FK   

       JOIN sys.tables PT ON PT.[object_id] = FK.parent_object_id

       JOIN ParentColumns AS PC ON PC.[object_id] = FK.parent_object_id AND PC.referenced_object_id = FK.referenced_object_id

       JOIN sys.tables RT ON RT.[object_id] = FK.referenced_object_id

       JOIN RefColumns AS RC ON RC.[object_id] = FK.referenced_object_id AND RC.parent_object_id = FK.parent_object_id

WHERE PT.name NOT IN ('dtproperties', 'sysdiagrams', '__RefactorLog')

       AND RT.name NOT IN ('dtproperties', 'sysdiagrams', '__RefactorLog')

ORDER BY PT.name

GO

 



If anyone find any error or think this can be improved then please do post your comment.

1 comment:

  1. Very helpful. Saved me some nightly hours.
    Thank You.
    Clemens / Austria

    ReplyDelete