Matches in DBpedia 2015-10 for { ?s ?p "In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. The subquery is evaluated once for each row processed by the outer query.Here is an example for a typical correlated subquery. In this example we are finding the list of all employees whose salary is above average for their departments.In the above query the outer query isand the inner query (the correlated subquery) isIn the above nested query the inner query has to be re-executed for each employee. (A sufficiently smart implementation may cache the inner query's result on a department-by-department basis, but even in the best case the inner query must be executed once per department. See "Optimizing correlated subqueries" below.)Correlated subqueries may appear elsewhere besides the WHERE clause; for example, this query uses a correlated subquery in the SELECT clause to print the entire list of employees alongside the average salary for each employee's department. Again, because the subquery is correlated with a column of the outer query, it must be re-executed for each row of the result."@en }
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- Correlated_subquery abstract "In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. The subquery is evaluated once for each row processed by the outer query.Here is an example for a typical correlated subquery. In this example we are finding the list of all employees whose salary is above average for their departments.In the above query the outer query isand the inner query (the correlated subquery) isIn the above nested query the inner query has to be re-executed for each employee. (A sufficiently smart implementation may cache the inner query's result on a department-by-department basis, but even in the best case the inner query must be executed once per department. See "Optimizing correlated subqueries" below.)Correlated subqueries may appear elsewhere besides the WHERE clause; for example, this query uses a correlated subquery in the SELECT clause to print the entire list of employees alongside the average salary for each employee's department. Again, because the subquery is correlated with a column of the outer query, it must be re-executed for each row of the result.".