grouping

指示列是否为聚合列。如果它是聚合列，则返回 0。否则，返回 1。

语法

GROUPING(col_expr)

参数

col_expr：在 GROUP BY 子句的 ROLLUP、CUBE 或 GROUPING SETS 扩展的表达式列表中指定的维度列的表达式。

示例

MySQL > select * from t;
+------+------+
| k1   | k2   |
+------+------+
| NULL | B    |
| NULL | b    |
| A    | NULL |
| A    | B    |
| A    | b    |
| a    | NULL |
| a    | B    |
| a    | b    |
+------+------+
8 rows in set (0.12 sec)

MySQL > SELECT k1, k2, GROUPING(k1), GROUPING(k2), COUNT(*) FROM t GROUP BY ROLLUP(k1, k2);
+------+------+--------------+--------------+----------+
| k1   | k2   | grouping(k1) | grouping(k2) | count(*) |
+------+------+--------------+--------------+----------+
| NULL | NULL |            1 |            1 |        8 |
| NULL | NULL |            0 |            1 |        2 |
| NULL | B    |            0 |            0 |        1 |
| NULL | b    |            0 |            0 |        1 |
| A    | NULL |            0 |            1 |        3 |
| a    | NULL |            0 |            1 |        3 |
| A    | NULL |            0 |            0 |        1 |
| A    | B    |            0 |            0 |        1 |
| A    | b    |            0 |            0 |        1 |
| a    | NULL |            0 |            0 |        1 |
| a    | B    |            0 |            0 |        1 |
| a    | b    |            0 |            0 |        1 |
+------+------+--------------+--------------+----------+
12 rows in set (0.12 sec)