SQL GROUP BY
Introduction
Results of a SELECT query can be grouped by one or more columns using the GROUP BY statement: all results with the same value in the grouped columns are aggregated together. This generates a table of partial results, instead of one result. GROUP BY can be used in conjunction with aggregation functions using the HAVING statement to define how non-grouped columns are aggregated.
Syntax
-
GROUP BY {
column-expression
| ROLLUP ( <group_by_expression> [ ,...n ] )
| CUBE ( <group_by_expression> [ ,...n ] )
| GROUPING SETS ( [ ,...n ] )
| () --calculates the grand total
} [ ,...n ] -
<group_by_expression> ::=
column-expression
| ( column-expression [ ,...n ] ) -
<grouping_set> ::=
() --calculates the grand total
| <grouping_set_item>
| ( <grouping_set_item> [ ,...n ] ) -
<grouping_set_item> ::=
<group_by_expression>
| ROLLUP ( <group_by_expression> [ ,...n ] )
| CUBE ( <group_by_expression> [ ,...n ] )
