SQL Server script to automatically create indexes for foreign keys
DECLARE @IndexName TABLE ([SQL] NVARCHAR(500));
WITH
v_NonIndexedFKColumns
AS
(
SELECT
[Table_Name] = OBJECT_NAME(a.[parent_object_id]),
[Column_Name] = b.[NAME]
FROM
sys.foreign_key_columns a
, sys.all_columns b
, sys.objects c
WHERE
a.[parent_column_id] = b.[column_id]
AND a.[parent_object_id] = b.[object_id]
AND b.[object_id] = c.[object_id]
AND c.[is_ms_shipped] = 0
EXCEPT
SELECT
[Table_Name] = OBJECT_NAME(a.[object_id]),
[Column_Name] = b.[NAME]
FROM
sys.index_columns a
, sys.all_columns b
, sys.objects c
WHERE
a.[object_id] = b.[object_id]
AND a.[key_ordinal] = 1
AND a.[column_id] = b.[column_id]
AND a.[object_id] = c.[object_id]
AND c.[is_ms_shipped] = 0
)
INSERT INTO @IndexName
([SQL])
SELECT
'CREATE INDEX [IX_' + v.[Table_Name] + '_' + v.[Column_Name] + ']'
+ 'ON [' + SCHEMA_NAME(fk.[schema_id]) + '].[' + v.[Table_Name] + '] ([' + v.[Column_Name] + ']);'
FROM
v_NonIndexedFKColumns v
, sys.all_columns c
, sys.all_columns c2
, sys.foreign_key_columns fkc
, sys.foreign_keys fk
WHERE
v.[Table_Name] = OBJECT_NAME(fkc.[parent_object_id])
AND v.[Column_Name] = c.[NAME]
AND fkc.[parent_column_id] = c.[column_id]
AND fkc.[parent_object_id] = c.[object_id]
AND fkc.[referenced_column_id] = c2.[column_id]
AND fkc.[referenced_object_id] = c2.[object_id]
AND fk.[object_id] = fkc.[constraint_object_id]
DECLARE @CurrentSQLCommand NVARCHAR(MAX);
DECLARE sqlCommandsCursor CURSOR FOR
SELECT [SQL]
FROM @IndexName;
OPEN sqlCommandsCursor;
FETCH NEXT FROM sqlCommandsCursor INTO @CurrentSQLCommand;
WHILE @@FETCH_STATUS = 0
BEGIN
-- Un-comment the line below to create the indexes
-- EXEC sp_executesql @CurrentSQLCommand;
PRINT @CurrentSQLCommand
FETCH NEXT FROM sqlCommandsCursor INTO @CurrentSQLCommand;
END
CLOSE sqlCommandsCursor;
DEALLOCATE sqlCommandsCursor;
I have recently run into a couple of SQL server databases with performance issues. Investigation showed the likely issue was they were missing indexes on several foreign keys. A teammate introduced me to the magic script above (originally from MSSQLTips.com) to automatically generate index creation scripts.