Nested tables

Nested tables can appear in a FROM clause with the TABLE keyword. They are an alternative to using a view with normal join semantics. The columns projected from a command contained in a nested table can be used in join criteria, WHERE clauses, and other contexts where you can use FROM clause projected columns.

A nested table can have correlated references to preceding FROM clause column references as long as INNER and LEFT OUTER joins are used. This is especially useful in cases where then nested expression is a procedure or function call.

Valid nested table example
select * from t1, TABLE(call proc(t1.x)) t2
Invalid nested table example

The following nested table example is invalid, because t1 appears after the nested table in the FROM clause:

select * from TABLE(call proc(t1.x)) t2, t1
Multiple execution

Using a correlated nested table can result in multiple executions of the table expression — one for each correlated row.

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