SUBQ CONDITION FOR KEY

SUBQ CONDITION FOR KEY is a search strategy of the SQL Optimizer.

This search strategy is selected if the following conditions are fulfilled:

?     The table has only one primary key column.

?     The values for the key column come from a subquery.

or

?     The table has a primary key in several columns.

?     Equality conditions are defined on all primary key columns that are located before the column with the subquery in the primary key.

?     On one column of the primary key, an IN condition is defined in the form of a subquery.

For every results row of the subquery, a part of the primary key is searched sequentially.

See also:

Equality Condition

IN Condition

Search Conditions for Key Columns

List of All Search Strategies