やりたいこと

group byで同じデータを集約するとき、複数行を1行の文字列としてまとめたい。
GROUP_CONCAT や ARRAY_TO_STRING のようなことをSQLServreで実装したい。

方法

STRING_AGG 集計関数を使うとできそう。

STRING_AGG (Transact-SQL) - SQL Server | Microsoft Learn
https://learn.microsoft.com/ja-jp/sql/t-sql/functions/string-agg-transact-sql

やってみる

TBL

Bunrui Col1
------ ----------
精肉     1:豚肉
精肉     2:牛肉
精肉     3:鶏肉
精肉     4:合挽
青果     1:トマト
青果     2:りんご
青果     3:きゅうり

STRING_AGG 集計関数のサンプル

SELECT
	 TBL.Bunrui
	,STRING_AGG( CONVERT(VARCHAR(max), TBL.Col1), ',') AS Result
FROM
	(
			SELECT '精肉' AS Bunrui, '1:豚肉' AS Col1
	UNION	SELECT '精肉' AS Bunrui, '2:牛肉' AS Col1
	UNION	SELECT '精肉' AS Bunrui, '3:鶏肉' AS Col1
	UNION	SELECT '精肉' AS Bunrui, '4:合挽' AS Col1
	UNION	SELECT '青果' AS Bunrui, '1:トマト' AS Col1
	UNION	SELECT '青果' AS Bunrui, '2:りんご' AS Col1
	UNION	SELECT '青果' AS Bunrui, '3:きゅうり' AS Col1
	) AS TBL
GROUP BY
	TBL.Bunrui
;

Bunrui Result
------ ------------------------------
精肉     1:豚肉,2:牛肉,3:鶏肉,4:合挽        
青果     1:トマト,2:りんご,3:きゅうり

集計関数内の並び替え

STRING_AGG の後ろに WITHIN GROUP を追加。

STRING_AGG 集計関数のサンプル (降順指定)

SELECT
	 TBL.Bunrui
	,STRING_AGG( CONVERT(VARCHAR(max), TBL.Col1), ',') WITHIN GROUP (ORDER BY TBL.Col1 DESC) AS Result
FROM
	(
			SELECT '精肉' AS Bunrui, '1:豚肉' AS Col1
	UNION	SELECT '精肉' AS Bunrui, '2:牛肉' AS Col1
	UNION	SELECT '精肉' AS Bunrui, '3:鶏肉' AS Col1
	UNION	SELECT '精肉' AS Bunrui, '4:合挽' AS Col1
	UNION	SELECT '青果' AS Bunrui, '1:トマト' AS Col1
	UNION	SELECT '青果' AS Bunrui, '2:りんご' AS Col1
	UNION	SELECT '青果' AS Bunrui, '3:きゅうり' AS Col1
	) AS TBL
GROUP BY
	TBL.Bunrui
;

Bunrui Result
------ ------------------------------
精肉     4:合挽,3:鶏肉,2:牛肉,1:豚肉        
青果     3:きゅうり,2:りんご,1:トマト