關於oracle LISTAGG函式的用法(以某個欄位相同情況下，將對應的另一個欄位連線起來)
阿新 • • 發佈：2019-01-30
SELECT department_id "Dept.",
LISTAGG(last_name, '; ') WITHIN GROUP (ORDER BY hire_date) "Employees"
FROM employees
GROUP BY department_id--以上為主功能 ORDER BY department_id; Dept. Employees ------ ------------------------------------------------------------ 10 Whalen 20 Hartstein; Fay 30 Raphaely; Khoo; Tobias; Baida; Himuro; Colmenares 40 Mavris 50 Kaufling; Ladwig; Rajs; Sarchand; Bell; Mallin; Weiss; Davie
department_id相同情況下，將last_name以“;”連線起來，連線時以hire_date排序之後的順序進行combine
在不使用group by的時候可以用over語法代替
SELECT department_id "Dept.", LISTAGG(last_name, '; ') WITHIN GROUP (ORDER BY hire_date) "Employees" <span style="background-color: rgb(255, 0, 0);">OVER(PARTITION BY department_id)</span> FROM employees
over的用法可以解決一個問題:group by的時候select欄位選擇的時候欄位必須在聚集函式中或者group by欄位中。用over方法可以在select欄位中加任意表中的欄位。