1.7.19 CQL: EXISTS

An exists restriction translates to a WHERE sub-query and is used to say that "each row returned in the main query must satisfy some condition expressed by another query".

Example

{[],
 se_lt_x :: [a-A, b-B],
 exists se_lt_y :: [d-A]}

compiles to:

SELECT
  x.b, x.a
FROM
  se_lt_x x
WHERE
  EXISTS (SELECT * FROM se_lt_y WHERE x.a = y.d)