# HAVING 子句HAVING clause

`HAVING`子句用于根据指定的条件筛选生成的结果 `GROUP BY`The `HAVING` clause is used to filter the results produced by `GROUP BY` based on the specified condition. 它通常与 GROUP by 子句一起使用。It is often used in conjunction with a GROUP BY clause.

## 语法Syntax

``````HAVING boolean_expression
``````

## 参数Parameters

• boolean_expressionboolean_expression

指定任何计算结果类型的表达式 `boolean`Specifies any expression that evaluates to a result type `boolean`. 两个或多个表达式可以使用逻辑运算符组合在一起 `AND` ， (， `OR` ) 。Two or more expressions may be combined together using the logical operators ( `AND`, `OR` ).

注意Note

子句中指定的表达式 `HAVING` 只能引用：The expressions specified in the `HAVING` clause can only refer to:

1. 常量Constants
2. "分组依据" 中显示的表达式Expressions that appear in GROUP BY
3. 聚合函数Aggregate functions

## 示例Examples

``````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|
+---+
``````