How can I find unindexed foreign keys in SQL Server
I have a SQL Server 2000 database with approximately 220 tables. These tables have a number foreign key relationships between them. Through performance analysis, we've discovered a number of these foreign key relationships are missing indexes. Instead of being reactive to performance problems, I'd like to be pro-active and find all foreign keys that are missing indexes.
How can I programmatically determine which foreign key are missing indexes?
SELECT *
FROM sys.foreign_keys fk
WHERE EXISTS
(
SELECT *
FROM sys.foreign_key_columns fkc
WHERE fkc.constraint_object_id = fk.object_id
AND NOT EXISTS
(
SELECT *
FROM sys.index_columns ic
WHERE ic.object_id = fkc.parent_object_id
AND ic.column_id = fkc.parent_column_id
AND ic.index_column_id = fkc.constraint_column_id
)
)
I don't have a copy of SQL Server 2000 handy, but you may need to change sys.foreign_key to sysforeignkeys etc., like described here .
This query selects all foreign keys which don't have an index covering all columns that comprise the key.
This supports multi-column foreign keys just as well.
This, however, will return a false positive if there is a composite index that covers all columns but they are not the leftmost columns in this index.
Like, if there is a FOREIGN KEY (col2, col3) and an index on (col1, col2, col3) , this will return that there is an index despite the fact this index is unusable for this foreign key.
这是一个适用于由同事编写的SQL Server 2000的答案：
/*
Description:
This script outputs a table with all the current database un-indexed foreign keys.
The table has three columns ( TableName , ColumnName, ForeignKeyName )
TableName: The table containing the un-indexed foreign key
ColumnName: The foreign key column that’s not indexed
ForeignKeyName: Name of foreign key witch column doesn’t have an index
*/
DECLARE
@TableName varchar(255),
@ColumnName varchar(255),
@ForeignKeyName sysname
SET NOCOUNT ON
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
DECLARE FKColumns_cursor CURSOR Fast_Forward FOR
SELECT cu.TABLE_NAME, cu.COLUMN_NAME, cu.CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS ic
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE cu ON ic.CONSTRAINT_NAME = cu.CONSTRAINT_NAME
WHERE ic.CONSTRAINT_TYPE = 'FOREIGN KEY'
CREATE TABLE #temp1(
TableName varchar(255),
ColumnName varchar(255),
ForeignKeyName sysname
)
OPEN FKColumns_cursor
FETCH NEXT FROM FKColumns_cursor INTO @TableName, @ColumnName, @ForeignKeyName
WHILE @@FETCH_STATUS = 0
BEGIN
IF ( SELECT COUNT(*)
FROM sysobjects o
INNER JOIN sysindexes x ON x.id = o.id
INNER JOIN syscolumns c ON o.id = c.id
INNER JOIN sysindexkeys xk ON c.colid = xk.colid AND o.id = xk.id AND x.indid = xk.indid
WHERE o.type in ('U')
AND xk.keyno <= x.keycnt
AND permissions(o.id, c.name) <> 0
AND (x.status&32) = 0
AND o.name = @TableName
AND c.name = @ColumnName
) = 0
BEGIN
INSERT INTO #temp1 SELECT @TableName, @ColumnName, @ForeignKeyName
END
FETCH NEXT FROM FKColumns_cursor INTO @TableName, @ColumnName, @ForeignKeyName
END
CLOSE FKColumns_cursor
DEALLOCATE FKColumns_cursor
SELECT * FROM #temp1 ORDER BY TableName
基于上述代码构建，以删除临时表并获取脚本以创建索引。
/*
Description:
*/
DECLARE
@SchemaName varchar(255),
@TableName varchar(255),
@ColumnName varchar(255),
@ForeignKeyName sysname
SET NOCOUNT ON
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
DECLARE FKColumns_cursor CURSOR Fast_Forward FOR
SELECT cu.TABLE_SCHEMA, cu.TABLE_NAME, cu.COLUMN_NAME, cu.CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS ic
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE cu ON ic.CONSTRAINT_NAME = cu.CONSTRAINT_NAME
WHERE ic.CONSTRAINT_TYPE = 'FOREIGN KEY'
CREATE TABLE #temp1(
SchemaName varchar(255),
TableName varchar(255),
ColumnName varchar(255),
ForeignKeyName sysname
)
OPEN FKColumns_cursor
FETCH NEXT FROM FKColumns_cursor INTO @SchemaName,@TableName, @ColumnName, @ForeignKeyName
WHILE @@FETCH_STATUS = 0
BEGIN
IF ( SELECT COUNT(*)
FROM sysobjects o
INNER JOIN sysindexes x ON x.id = o.id
INNER JOIN syscolumns c ON o.id = c.id
INNER JOIN sysindexkeys xk ON c.colid = xk.colid AND o.id = xk.id AND x.indid = xk.indid
WHERE o.type in ('U')
AND xk.keyno <= x.keycnt
AND permissions(o.id, c.name) <> 0
AND (x.status&32) = 0
AND o.name = @TableName
AND c.name = @ColumnName
) = 0
BEGIN
INSERT INTO #temp1 SELECT @SchemaName, @TableName, @ColumnName, @ForeignKeyName
END
FETCH NEXT FROM FKColumns_cursor INTO @SchemaName,@TableName, @ColumnName, @ForeignKeyName
END
CLOSE FKColumns_cursor
DEALLOCATE FKColumns_cursor
SELECT 'CREATE INDEX IDX_' + ForeignKeyName + ' ON ' + SchemaName + '.' + TableName + '(' + ColumnName +')'
FROM #temp1
ORDER BY TableName
drop table #temp1
上一篇: 在sql server中自动增加id