Sub-Query in SQL

Question

Hi Friends I want to know the Properties of Sub-Query in SQL ?

nallya · Answer

Sub-queries are often referred to as sub-selects as they allow a SELECT statement to be executed arbitrarily within the body of another SQL statement. A sub-query is executed by enclosing it in a set of parentheses. Sub-queries are generally used to return a single row as an atomic value though they may be used to compare values against multiple rows with the IN keyword. A subquery is a SELECT statement that is nested within another T-SQL statement. A subquery SELECT statement if executed independently of the T-SQL statement in which it is nested will return a resultset. Meaning a subquery SELECT statement can standalone and is not depended on the statement in which it is nested. A subquery SELECT statement can return any number of values and can be found in the column list of a SELECT statement a FROM GROUP BY HAVING and/or ORDER BY clauses of a T-SQL statement. A Subquery can also be used as a parameter to a function call. Basically a subquery can be used anywhere an expression can be used. ( Read More Here ) Refer This: http://blog.sqlauthority.com/2008/09/13/sql-server-2008-interview-questions-and-answers-part-2/