Subquery
Subquery is a query whithin in a query. It is also called as Inner query or Nested query. A subquery is usually added in the WHERE clause of the sql statement. Usually, a subquery is used when we know how to search for a value using a SELECT statement, but do not know the exact value.
Subquery is a query whithin in a query. It is also called as Inner query or Nested query. A subquery is usually added in the WHERE clause of the sql statement. Usually, a subquery is used when we know how to search for a value using a SELECT statement, but do not know the exact value.
Rules for Subqueries
· Must be enclosed in parentheses
· Can be the object of an IN or NOT IN clause
· Can be the object of EXISTS or NOT EXISTS clause
· Support quantifiers ALL, ANY, SOME
· Support LIKE or NOT LIKE used with a quantifier
· Can specify more than one column to match
· Generate a DISTINCT list of values
· Cannot use ORDER BY (within the subquery
statement).
·
Keep in mind that a maximum of 64
tables/views can be specified in an SQL
statement.
statement.
