如何使我的結果字符串1000個字符長的使用LISTAGG

Question

我想我的結果字符串限制爲1000個字符，當我使用LISTAGG。

這裏是我的示例查詢：

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

如果names規模超過1000個字符長，我只是想只有1000個字符，而忽略剩餘。

Answer 1

途徑TRUNC字符串1000個字符是：

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

如果你希望停止運行conacatenating的長度條件EMPLOYEE_NAME，你應該寫自己的PL \ SQL PROC，LISTAGG concats所有數據。

好吧，如果你想讓它在單一的查詢，試試這個。首先，calc下所有連接字符串的總長度加2「」符號：

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

然後調用LISTAGG此子查詢：

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;