Let’s say, just theoretically, you wanted to demo a query that takes SQL Server a long time to compile.
And in order to make SQL Server’s job tougher, you wanted to create the maximum number of indexes possible on a table.
You might do something like this:
SELECT TOP 999 'CREATE INDEX [IX_' + c1.COLUMN_NAME + '_' + c2.COLUMN_NAME + '_' + c3.COLUMN_NAME + ']'+ ' ON [' + c1.TABLE_SCHEMA + '].[' + c1.TABLE_NAME + '] '
+ '([' + c1.COLUMN_NAME + '], [' + c2.COLUMN_NAME + '], [' + c3.COLUMN_NAME + ']);'
FROM INFORMATION_SCHEMA.COLUMNS c1
INNER JOIN INFORMATION_SCHEMA.COLUMNS c2 ON c1.TABLE_SCHEMA = c2.TABLE_SCHEMA AND c1.TABLE_NAME = c2.TABLE_NAME
AND c1.COLUMN_NAME <> c2.COLUMN_NAME
AND (c2.CHARACTER_MAXIMUM_LENGTH <> -1 OR c2.CHARACTER_MAXIMUM_LENGTH IS NULL)
INNER JOIN INFORMATION_SCHEMA.COLUMNS c3 ON c1.TABLE_SCHEMA = c3.TABLE_SCHEMA AND c1.TABLE_NAME = c3.TABLE_NAME
AND c3.COLUMN_NAME NOT IN (c1.COLUMN_NAME, c2.COLUMN_NAME)
AND (c3.CHARACTER_MAXIMUM_LENGTH <> -1 OR c3.CHARACTER_MAXIMUM_LENGTH IS NULL)
WHERE c1.TABLE_SCHEMA = 'dbo' AND c1.TABLE_NAME = 'Users'
AND (c1.CHARACTER_MAXIMUM_LENGTH <> -1 OR c1.CHARACTER_MAXIMUM_LENGTH IS NULL)
ORDER BY c3.COLUMN_NAME, c2.COLUMN_NAME
Which would generate output like this:
Look, you’re the one who comes here to “learn stuff”
The CHARACTER_MAXIMUM_LENGTH <> -1 OR IS NULL stuff is because I don’t want to try to index NVARCHAR(MAX) fields, but I do want to index NVARCHAR(50) fields.
The ORDER BY is because I wanted to get a wide variety of leading fields. If I just ordered by c1.COLUMN_NAME, I wouldn’t get all of the first fields covered in the first 999 indexes. (And I’m not even using a large table.)
I could have dumped all these into strings and executed them, but depending on the speed of the system, the demos I’m trying to do, the fields in the indexes, etc, I may not want them all created right away. Sometimes I experiment with just 25-50 indexes before moving on to, uh, 999.
Brent Ozar
I make Microsoft SQL Server faster and more reliable. I love teaching, travel, and laughing.
