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：

  1. SELECT a, b, SUM( c ) FROM tab1 GROUP BY GROUPING SETS ( (a, b), (a), (b), ( ) );

其查询结果等价于：

  1. SELECT a, b, SUM( c ) FROM tab1 GROUP BY a, b
  2. UNION
  3. SELECT a, null, SUM( c ) FROM tab1 GROUP BY a
  4. UNION
  5. SELECT null, b, SUM( c ) FROM tab1 GROUP BY b
  6. UNION
  7. SELECT null, null, SUM( c ) FROM tab1

GROUPING(expr) 指示一个列是否为聚合列，如果是聚合列为0，否则为1

GROUPING_ID(expr [ , expr [ , ... ] ]) 与GROUPING 类似， GROUPING_ID根据指定的column 顺序，计算出一个列列表的 bitmap 值，每一位为GROUPING的值. GROUPING_ID()函数返回位向量的十进制值。

Syntax

  1. SELECT ...
  2. FROM ...
  3. [ ... ]
  4. GROUP BY [
  5.     , ... |
  6.     GROUPING SETS [, ...] (  groupSet [ , groupSet [ , ... ] ] ) |
  7.     ROLLUP(expr  [ , expr [ , ... ] ]) |
  8.     expr  [ , expr [ , ... ] ] WITH ROLLUP |
  9.     CUBE(expr  [ , expr [ , ... ] ]) |
  10.     expr  [ , expr [ , ... ] ] WITH CUBE
  11.     ]
  12. [ ... ]

Parameters

groupSet 表示 select list 中的列，别名或者表达式组成的集合 groupSet ::= { ( expr [ , expr [ , ... ] ] )}

expr 表示 select list 中的列，别名或者表达式

Note

doris 支持类似PostgreSQL 语法, 语法实例如下

  1. SELECT a, b, SUM( c ) FROM tab1 GROUP BY GROUPING SETS ( (a, b), (a), (b), ( ) );
  2. SELECT a, b,c, SUM( d ) FROM tab1 GROUP BY ROLLUP(a,b,c)
  3. SELECT a, b,c, SUM( d ) FROM tab1 GROUP BY CUBE(a,b,c)

ROLLUP(a,b,c) 等价于如下GROUPING SETS 语句

  1. GROUPING SETS (
  2. (a,b,c),
  3. ( a, b ),
  4. ( a),
  5. ( )
  6. )

CUBE ( a, b, c ) 等价于如下GROUPING SETS 语句

  1. GROUPING SETS (
  2. ( a, b, c ),
  3. ( a, b ),
  4. ( a,    c ),
  5. ( a       ),
  6. (    b, c ),
  7. (    b    ),
  8. (       c ),
  9. (         )
  10. )

example

下面是一个实际数据的例子

  1. > SELECT * FROM t;
  2. +------+------+------+
  3. | k1   | k2   | k3   |
  4. +------+------+------+
  5. | a    | A    |    1 |
  6. | a    | A    |    2 |
  7. | a    | B    |    1 |
  8. | a    | B    |    3 |
  9. | b    | A    |    1 |
  10. | b    | A    |    4 |
  11. | b    | B    |    1 |
  12. | b    | B    |    5 |
  13. +------+------+------+
  14. 8 rows in set (0.01 sec)
  16. > SELECT k1, k2, SUM(k3) FROM t GROUP BY GROUPING SETS ( (k1, k2), (k2), (k1), ( ) );
  17. +------+------+-----------+
  18. | k1   | k2   | sum(`k3`) |
  19. +------+------+-----------+
  20. | b    | B    |         6 |
  21. | a    | B    |         4 |
  22. | a    | A    |         3 |
  23. | b    | A    |         5 |
  24. | NULL | B    |        10 |
  25. | NULL | A    |         8 |
  26. | a    | NULL |         7 |
  27. | b    | NULL |        11 |
  28. | NULL | NULL |        18 |
  29. +------+------+-----------+
  30. 9 rows in set (0.06 sec)
  32. > SELECT k1, k2, GROUPING_ID(k1,k2), SUM(k3) FROM t GROUP BY GROUPING SETS ((k1, k2), (k1), (k2), ());
  33. +------+------+---------------+----------------+
  34. | k1   | k2   | grouping_id(k1,k2) | sum(`k3`) |
  35. +------+------+---------------+----------------+
  36. | a    | A    |             0 |              3 |
  37. | a    | B    |             0 |              4 |
  38. | a    | NULL |             1 |              7 |
  39. | b    | A    |             0 |              5 |
  40. | b    | B    |             0 |              6 |
  41. | b    | NULL |             1 |             11 |
  42. | NULL | A    |             2 |              8 |
  43. | NULL | B    |             2 |             10 |
  44. | NULL | NULL |             3 |             18 |
  45. +------+------+---------------+----------------+
  46. 9 rows in set (0.02 sec)

keyword

GROUP, GROUPING, GROUPING_ID, GROUPING_SETS, GROUPING SETS, CUBE, ROLLUP