Syntax
{ query_factor |
query_expression { UNION | MINUS | EXCEPT } [ ALL ]
{ query_factor | ( query_expression ) ordering }
}
Syntax Elements
-
query_factor
-
-
query_expression
-
- UNION
- MINUS
- EXCEPT
- Set operators specifying how the two or more queries or subqueries are to combine and determine what result rows are required to be returned.
- ALL
- Allows duplicate rows to be returned.
-
ordering
-
ORDER BY expr_spec [,...]
-
expr_spec
-
expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ]
-
expression
- An expression used in the ORDER BY clause to determine the sort order of returned rows in the result.
- ASC
- That the results are to be ordered in ascending sort order.
- If the sort field is a character string, the system orders it in ascending order according to the definition of the collation sequence for the current session.
- The default order is ASC.
- DESC
- That the results are to be ordered in descending sort order.
- If the sort field is a character string, the system orders it in descending order according to the definition of the collation sequence for the current session.
- NULLS FIRST
- NULL results are to be listed first.
- NULLS LAST
- NULL results are to be listed last.