.NET C C++ CSS DBA General HTML Java JavaScript JSP JUnit MySQL Networking Oracle Perl Perl PHP PL/SQL RSS Software QA SQL Server Struts Unix Windows XHTML XML

What Is a Subquery

Q

What Is a Subquery? - Oracle DBA FAQ - Understanding SQL SELECT Query Statements

✍: FYIcenter.com

A

A subquery is a SELECT statement used as part of the selection criteria of the main SELECT statement. The subquery specified in the WHERE clause will be evaluated repeated on each row of the selection base table. The output of the subquery will be used in the final evaluation of the criteria. Usually, subqueries are used in the following boolean operations:

  • "expression IN (subquery)"
  • "expression NOT IN (subquery)"
  • "EXISTS (subquery)"
  • "NOT EXISTS (subquery)"

2007-04-19, 5179👍, 0💬

.NET C C++ CSS DBA General HTML Java JavaScript JSP JUnit MySQL Networking Oracle Perl Perl PHP PL/SQL RSS Software QA SQL Server Struts Unix Windows XHTML XML