SQL SERVER – Drop All the Foreign Key Constraint in Database – Create All the Foreign Key Constraint in Database

SET NOCOUNT ON

DECLARE @table TABLE (
 RowId INT PRIMARY KEY IDENTITY(1, 1)
 ,ForeignKeyConstraintName NVARCHAR(200)
 ,ForeignKeyConstraintTableSchema NVARCHAR(200)
 ,ForeignKeyConstraintTableName NVARCHAR(200)
 ,ForeignKeyConstraintColumnName NVARCHAR(200)
 ,PrimaryKeyConstraintName NVARCHAR(200)
 ,PrimaryKeyConstraintTableSchema NVARCHAR(200)
 ,PrimaryKeyConstraintTableName NVARCHAR(200)
 ,PrimaryKeyConstraintColumnName NVARCHAR(200)
 )

INSERT INTO @table (
 ForeignKeyConstraintName
 ,ForeignKeyConstraintTableSchema
 ,ForeignKeyConstraintTableName
 ,ForeignKeyConstraintColumnName
 )
SELECT U.CONSTRAINT_NAME
 ,U.TABLE_SCHEMA
 ,U.TABLE_NAME
 ,U.COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE U
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C ON U.CONSTRAINT_NAME = C.CONSTRAINT_NAME
WHERE C.CONSTRAINT_TYPE = 'FOREIGN KEY'

UPDATE @table
SET PrimaryKeyConstraintName = UNIQUE_CONSTRAINT_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS R ON T.ForeignKeyConstraintName = R.CONSTRAINT_NAME

UPDATE @table
SET PrimaryKeyConstraintTableSchema = TABLE_SCHEMA
 ,PrimaryKeyConstraintTableName = TABLE_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.TABLE_CONSTRAINTS C ON T.PrimaryKeyConstraintName = C.CONSTRAINT_NAME

UPDATE @table
SET PrimaryKeyConstraintColumnName = COLUMN_NAME
FROM @table T
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE U ON T.PrimaryKeyConstraintName = U.CONSTRAINT_NAME

--SELECT * FROM @table
--DROP CONSTRAINT:
SELECT '
ALTER TABLE [' + ForeignKeyConstraintTableSchema + '].[' + ForeignKeyConstraintTableName + ']
DROP CONSTRAINT ' + ForeignKeyConstraintName + '
 
GO'
FROM @table

--ADD CONSTRAINT:
SELECT '
ALTER TABLE [' + ForeignKeyConstraintTableSchema + '].[' + ForeignKeyConstraintTableName + ']
ADD CONSTRAINT ' + ForeignKeyConstraintName + ' FOREIGN KEY(' + ForeignKeyConstraintColumnName + ') REFERENCES [' + PrimaryKeyConstraintTableSchema + '].[' + PrimaryKeyConstraintTableName + '](' + PrimaryKeyConstraintColumnName + ')
 
GO'
FROM @table
GO






Reference:https://blog.sqlauthority.com/2014/04/11/sql-server-drop-all-the-foreign-key-constraint-in-database-create-all-the-foreign-key-constraint-in-database/