Friday, November 30, 2018

MSSQL: Recreate Foreign Keys

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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 + ';'
FROM
@table

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

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