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SUBQ CONDITION FOR INDEX is a search strategy of the SQL optimizer.

When Can the System Use This Strategy?

The database system can use this search strategy if one of the following conditions is met in a subquery:

  • For the first k columns of an index, the search condition contains equality or range conditions ( 1 ≤ k < n, n= number of indexed columns).

  • The search condition contains one equality condition for all columns of an index.

How Does the System Access the Data?

The database system performs a sequential search on part of the index for each results row of the subquery.