Indexing for Foreign Keys in SQL Server?

Question

I am using SQL Server.

Is it needed to use index for any foreign key for improving speed?

Or will SQL Server do it automatically when I define foreign keys?

Index tuning is an art. And you don't want too many or too little. Here is a helper, maybe : simple-talk.com/sql/learn-sql-server/… — granadaCoder
– granadaCoder, Commented Aug 13, 2014 at 22:09

Lmu92 · Accepted Answer · 2014-08-13 21:23:18Z

2

SQL Server will not automatically add an index when creating a foreign key. An index on that foreign key may help improve performance. But usually there are more columns needed from that table, so it might be a better decision to add a few more columns needed (either being part of the index or as included columns).

answered Aug 13, 2014 at 21:23

Lmu92

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2 Comments

pmbAustin Over a year ago

More specific note: Indexing foreign key columns mainly speeds up DELETE operations, as it can quickly tell if the row can be deleted without having to scan other tables.

marc_s Over a year ago

@pmbAustin: and having an index on the foreign key column also helps with JOIN operations, since the FK data can be read in sorted order!

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