📌  相关文章
📜  Oracle HAVING子句

📅  最后修改于: 2020-11-15 03:50:48             🧑  作者: Mango

Oracle HAVING子句

在Oracle中，HAVING子句与GROUP BY子句一起使用以限制条件为TRUE时返回的行的组。

句法：

SELECT expression1, expression2, ... expression_n, 
 aggregate_function (aggregate_expression)
FROM tables
WHERE conditions
GROUP BY expression1, expression2, ... expression_n
HAVING having_condition;

参数：

expression1，expression2，… expression_n：它指定未封装在聚合函数的表达式。这些表达式必须包含在GROUP BY子句中。

gregation_function：它指定聚合函数，即SUM，COUNT，MIN，MAX或AVG函数。

gregation_expression：指定聚合函数所基于的列或表达式。

表：它指定要从中检索记录的表。

条件：它指定要选择的记录必须满足的条件。

hading_conditions：指定仅适用于汇总结果的条件，以限制返回的行的组。

Oracle HAVING示例：(具有GROUP BY SUM函数)

让我们来一张桌子“ salesdepartment”

销售部门表：

CREATE TABLE  "SALESDEPARTMENT" 
   (    "ITEM" VARCHAR2(4000), 
    "SALE" NUMBER, 
    "BILLING_ADDRESS" VARCHAR2(4000)
   )
/

执行此查询：

 
SELECT item, SUM(sale) AS "Total sales"
FROM salesdepartment
GROUP BY item
HAVING SUM(sale) < 1000;

输出：

Oracle HAVING示例：(具有GROUP BY COUNT函数)

让我们来一张桌子“客户”

客户表：

CREATE TABLE  "CUSTOMERS" 
   (    "NAME" VARCHAR2(4000), 
    "AGE" NUMBER, 
    "SALARY" NUMBER, 
    "STATE" VARCHAR2(4000)
   )
/

执行此查询：

SELECT state, COUNT(*) AS "Number of customers"
FROM customers
WHERE salary > 10000
GROUP BY state
HAVING COUNT(*) >= 2;

输出：

Oracle HAVING示例：(具有GROUP BY MIN函数)

让我们来个表格“员工”

员工表：

CREATE TABLE  "EMPLOYEES" 
   (    "EMP_ID" NUMBER, 
    "NAME" VARCHAR2(4000), 
    "AGE" NUMBER, 
    "DEPARTMENT" VARCHAR2(4000), 
    "SALARY" NUMBER
   )
/

执行此查询：

SELECT department, 
MIN(salary) AS "Lowest salary"
FROM employees
GROUP BY department
HAVING MIN(salary) < 15000;

输出量

Oracle HAVING示例：(具有GROUP BY MAX函数)

执行此查询：

SELECT department,
MAX(salary) AS "Highest salary"
FROM employees
GROUP BY department
HAVING MAX(salary) > 30000;

输出：