Syntax : EXISTS Logical Expression - Teradata Database

where:

Syntax element …	Specifies …
EXISTS	the EXISTS (∃) logical quantifier. See SQL Functions, Operators, Expressions, and Predicates for details.
subquery	any valid SQL subquery.

Subqueries are ANSI SQL:2011-compliant.

The rules and restrictions are:

You can specify up to 64 levels of nesting of subqueries. Each subquery can specify a maximum of 128 tables or single‑table views.

This limit is established using the DBS Control field MaxParseTreeSegs. The value for MaxParseTreeSegs must be set to 256 or higher define an upper limit of 64 subquery nesting levels.

See Utilities: Volume 1 (A-K) for information about how to change the MaxParseTreeSegs setting in the DBS Control record.

Subqueries in search conditions cannot contain SELECT AND CONSUME statements.

Subqueries in search conditions cannot specify the TOP n operator.