oracle having
时间: 2023-10-21 09:35:51 浏览: 39
"having" is a clause used in SQL to filter data after a SELECT statement has been executed. It is used to specify a condition that must be satisfied by the data returned from the query. The "having" clause is similar to the "where" clause, but it is used to filter data based on aggregate functions, such as COUNT, SUM, AVG, and MAX. The "having" clause is used after the "group by" clause to filter the results based on the aggregated data.
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oraclehaving用法
`HAVING`是`SQL`中用于对`GROUP BY`分组后的数据进行过滤的关键字,用于筛选聚合后的结果集。它通常与`GROUP BY`关键字一起使用,以确定哪些组或行满足指定的条件。`HAVING`子句中的条件只能使用聚合函数或`GROUP BY`子句中的列。
一个基本的`HAVING`语句的语法如下:
```
SELECT column_name(s)
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition;
```
其中,`column_name(s)`表示要查询的列名,`table_name`表示要查询的表名,`condition`表示查询条件,`GROUP BY`子句用于指定要分组的列,`HAVING`子句用于筛选分组后的结果集。
以下是一个例子,它将`employees`表按照`department`分组,并只返回`department`的平均薪资大于5000的记录:
```
SELECT department, AVG(salary)
FROM employees
GROUP BY department
HAVING AVG(salary) > 5000;
```
需要注意的是,`HAVING`子句只能用于`GROUP BY`语句,如果没有对查询结果进行分组,则不能使用`HAVING`关键字。
oracle having count
Oracle中的HAVING COUNT是一种用于聚合函数的筛选条件,它可以在GROUP BY子句之后使用,用于过滤聚合结果中的数据。HAVING COUNT通常用于统计某个字段的数量,并筛选出满足条件的记录。例如,可以使用HAVING COUNT来查找某个表中出现次数超过一定阈值的记录。