HAVING 子句
描述
HAVING 子句用于根据指定的条件过滤 GROUP BY 生成的结果。它通常与 GROUP BY 子句一起使用。
语法
HAVING boolean_expression
参数
-
boolean_expression
指定任何计算结果为
boolean类型的表达式。可以使用逻辑运算符（AND、OR）将两个或多个表达式组合在一起。注意
HAVING子句中指定的表达式只能引用- 常量
- 出现在 GROUP BY 中的表达式
- 聚合函数
示例
CREATE TABLE dealer (id INT, city STRING, car_model STRING, quantity INT);
INSERT INTO dealer VALUES
(100, 'Fremont', 'Honda Civic', 10),
(100, 'Fremont', 'Honda Accord', 15),
(100, 'Fremont', 'Honda CRV', 7),
(200, 'Dublin', 'Honda Civic', 20),
(200, 'Dublin', 'Honda Accord', 10),
(200, 'Dublin', 'Honda CRV', 3),
(300, 'San Jose', 'Honda Civic', 5),
(300, 'San Jose', 'Honda Accord', 8);
-- `HAVING` clause referring to column in `GROUP BY`.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING city = 'Fremont';
+-------+---+
| city|sum|
+-------+---+
|Fremont| 32|
+-------+---+
-- `HAVING` clause referring to aggregate function.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING sum(quantity) > 15;
+-------+---+
| city|sum|
+-------+---+
| Dublin| 33|
|Fremont| 32|
+-------+---+
-- `HAVING` clause referring to aggregate function by its alias.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING sum > 15;
+-------+---+
| city|sum|
+-------+---+
| Dublin| 33|
|Fremont| 32|
+-------+---+
-- `HAVING` clause referring to a different aggregate function than what is present in
-- `SELECT` list.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING max(quantity) > 15;
+------+---+
| city|sum|
+------+---+
|Dublin| 33|
+------+---+
-- `HAVING` clause referring to constant expression.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING 1 > 0 ORDER BY city;
+--------+---+
| city|sum|
+--------+---+
| Dublin| 33|
| Fremont| 32|
|San Jose| 13|
+--------+---+
-- `HAVING` clause without a `GROUP BY` clause.
SELECT sum(quantity) AS sum FROM dealer HAVING sum(quantity) > 10;
+---+
|sum|
+---+
| 78|
+---+