GROUP BY

# GROUP BY # description GROUP BY GROUPING SETS ｜ CUBE ｜ ROLLUP 是对 GROUP BY 子句的扩展，它能够在一个 GROUP BY 子句中实现多个集合的分组的聚合。其结果等价于将多个相应 GROUP BY 子句进行 UNION 操作。 GROUP BY 子句是只含有一个元素的 GROUP BY GROUPING SETS 的特例。 例如，GROUPING SETS 语句： SELECT a, b, SUM( c ) FROM tab1 GROUP BY GROUPING SETS ( (a, b), (a), (b), ( ) ); 其查询结果等价于： SELECT a, b, SUM( c ) FROM tab1 GROUP ...阅读全文