STRING_AGG 配合 WITHIN GROUP 的使用
syntax：
STRING_AGG ( expression, separator ) [ <order_clause> ]
<order_clause> ::=
WITHIN GROUP ( ORDER BY <order_by_expression_list> [ ASC | DESC ] )
一、STRING_AGG
範例：
select STRING_AGG(Name,', ') from
(
SELECT 1 AS No, 'Bill' AS Name, 30 AS age
UNION
SELECT 2 AS No, 'Mary' AS Name, 15 AS age
UNION
SELECT 3 AS No, 'Json' AS Name, 30 AS age
UNION
SELECT 4 AS No, 'Tim' AS Name, 15 AS age
) p
說明：
其用途為將某欄位的 n 筆記錄串成一筆記錄。
二、STRING_AGG 配合 WITHIN GROUP 的使用
範例：
select age, STRING_AGG(Name,', ') WITHIN GROUP (order by No desc) from
(
SELECT 1 AS No, 'Bill' AS Name, 30 AS age
UNION
SELECT 2 AS No, 'Mary' AS Name, 15 AS age
UNION
SELECT 3 AS No, 'Json' AS Name, 30 AS age
UNION
SELECT 4 AS No, 'Tim' AS Name, 15 AS age
) p
group by age
說明：
當你有使用到群組並想排序串記錄時，則可加上 WITHIN GROUP。
參考資料：