Index Column Order and Selectivity

Erik Darling gives us multiverse indexing:

Missing index request column order is pretty basic.

Instead, we’re gonna add these:

CREATE INDEX ix_spaces
ON dbo.Posts(ParentId, Score);

 
CREATE INDEX ix_tabs
ON dbo.Posts(Score, ParentId);

SQL Server is capable of using both intelligently. This is something I generally don’t like to do, but if you have queries which absolutely need differently-ordered index columns, it can make sense to do this. Just don’t expect SQL Server’s missing index DMV to tell you which order they should be in.

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