Common table expressions are defined using the WITH clause, which precedes the SELECT keyword in a SELECT statement. The content of the clause defines one or more temporary views that are known only within the scope of a single SELECT statement and that may be referenced elsewhere in the statement. The syntax of this clause mimics that of the CREATE VIEW statement.
Common table expressions are useful and may be necessary if a query involves multiple aggregate functions or defines a view within a stored procedure that references program variables. Common table expressions also provide a convenient means to temporarily store sets of values.
Multiple correlation names
Multiple table expressions
Where common table expressions are permitted
Typical applications of common table expressions
Recursive common table expressions
Parts explosion problem
Least distance problem
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