Is an index needed for a primary key in SQLite?

sqlite indexing primary-key
Marek Jedliński picture Marek Jedliński · Jul 31, 2010 · Viewed 38.4k times · Source

When an integer column is marked as a primary key in an SQLite table, should an index be explicitly created for it as well? SQLite does not appear to automatically create an index for a primary key column, but perhaps it indexes it anyway, given its purpose? (I will be searching on that column all the time).

Would the situation be any different for a string primary key?

Answer

hvgotcodes picture hvgotcodes · Jul 31, 2010

It does it for you.

INTEGER PRIMARY KEY columns aside, both UNIQUE and PRIMARY KEY constraints are implemented by creating an index in the database (in the same way as a "CREATE UNIQUE INDEX" statement would). Such an index is used like any other index in the database to optimize queries. As a result, there often no advantage (but significant overhead) in creating an index on a set of columns that are already collectively subject to a UNIQUE or PRIMARY KEY constraint.

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