listagg within group
时间: 2023-10-26 16:05:11 浏览: 73
`LISTAGG` is an aggregate function in SQL that concatenates the values of a specified column into a single string. The `WITHIN GROUP` clause allows you to specify the order in which the values should be concatenated.
Here's an example usage of `LISTAGG` with `WITHIN GROUP`:
```sql
SELECT department_id,
LISTAGG(last_name, ', ') WITHIN GROUP (ORDER BY last_name) AS employees
FROM employees
GROUP BY department_id;
```
In this example, the `LISTAGG` function concatenates the `last_name` values from the `employees` table for each department, with the names ordered alphabetically. The result is a comma-separated string of employees' last names for each department.
相关问题
listagg within group
Listagg WITHIN GROUP是Oracle数据库的一个函数,用于将多行数据合并成一行,并通过指定的分隔符进行分割。它的语法是:
SELECT listagg(column_name, 'delimiter') WITHIN GROUP (ORDER BY column_name) alias
FROM table_name
GROUP BY column_name;
其中,column_name是要合并的列名,delimiter是分隔符,alias是合并后的列的别名。该函数首先根据ORDER BY子句对数据进行排序,然后将排序后的值按照指定的分隔符进行拼接。这样可以将多个行的数据合并成一行,并以指定的方式进行分割。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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listagg within group用法
listagg within group是Oracle数据库中的一个聚合函数,用于将多行数据合并为一个字符串,并且还可以在合并时指定排序规则。
使用listagg within group的语法如下:
```
LISTAGG(column, delimiter) WITHIN GROUP (ORDER BY column ASC/DESC) [OVER (PARTITION BY column)]
```
其中:
- `column`表示要合并的列名。
- `delimiter`表示用于分隔合并结果的字符。
- `ORDER BY column ASC/DESC`用于指定合并时的排序规则,默认情况下是按照查询结果集中的顺序进行合并。
- `PARTITION BY column`可选,用于对查询结果集进行分区,每个分区都会独立地进行合并操作。
下面是一个示例,假设有一个名为"employees"的表,包含两列"employee_name"和"department_name":
```
SELECT department_name, LISTAGG(employee_name, ', ') WITHIN GROUP (ORDER BY employee_name) AS employees
FROM employees
GROUP BY department_name;
```
以上查询将按照部门对员工姓名进行分组,并将每个部门的员工姓名用逗号和空格分隔合并为一个字符串。
注意:listagg within group函数在Oracle 11g版本及以上才可用。
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