"A subquery that cannot be evaluated independently, but depends on the outer query for its results. Also called a repeating subquery, since the subquery is executed once for each row that might be selected by the outer query. See also nested query." (Karen Paulsell et al, "Sybase SQL Server: Performance and Tuning Guide", 1996)
"A repeating subquery. Many queries can be evaluated by executing the subquery once and substituting the resulting value or values into the WHERE clause of the outer query. In queries that include a correlated subquery, the subquery depends on the outer query for its values. This means that the subquery is executed repeatedly, one time for each row that is selected by the outer query." (Microsoft Corporation, "SQL Server 7.0 System Administration Training Kit", 1999)
"A subquery that references a column in an outer statement. The inner query is executed for each candidate row in the outer statement." (Anthony Sequeira & Brian Alderman, "The SQL Server 2000 Book", 2003)
"A subquery that contains a reference to a column in the main, or parent, query." (Bob Bryla, "Oracle Database Foundations", 2004)
"A subquery that a DBMS cannot process completely before turning to the outer query. The DBMS must execute the subquery repeatedly for every row in the outer query." (Jan L Harrington, "SQL Clearly Explained 3rd Ed. ", 2010)
"A subquery that contains a correlated reference." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)
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