Question

我想在使用LISTAGG时将结果字符串限制为1000个字符。

以下是我的示例查询：

SELECT LISTAGG(EMPLOYEE_NAME,', ') WITHIN GROUP (ORDER BY EMPLOYEE_NAME) AS NAMES
FROM TB_EMPLOYEE;

如果NAMES大小超过1000个字符，我只想要1000个字符并忽略其余字符。

Answer 1

将字符串截断为1000个字符的方法是：

SELECT SUBSTR(LISTAGG(EMPLOYEE_NAME,', ') WITHIN GROUP 
    (ORDER BY EMPLOYEE_NAME), 1, 1000) AS NAMES FROM TB_EMPLOYEE;

如果你想在运行时停止在长度条件下连接EMPLOYEE_NAME，你应该编写自己的PL \ SQL proc，LISTAGG汇总所有数据。

好的，如果您想在单个查询中进行，请尝试此操作。首先，计算所有连接字符串的总长度加上2，'，'符号：

SELECT EMPLOYEE_NAME, SUM(LENGTH(EMPLOYEE_NAME)+2) over (ORDER BY EMPLOYEE_NAME) FROM TB_EMPLOYEE;

然后为这个子查询调用LISTAGG：

SELECT LISTAGG(EMPLOYEE_NAME,', ') WITHIN GROUP 
(ORDER BY EMPLOYEE_NAME) AS NAMES FROM (
  SELECT EMPLOYEE_NAME, SUM(LENGTH(EMPLOYEE_NAME)+2) over 
  (ORDER BY EMPLOYEE_NAME) slide_length FROM TB_EMPLOYEE )
WHERE slide_length < 1000;

如何使用LISTAGG使我的结果字符串长1000个字符

1 个答案: