SqlServer 对分组的内容进行拼接-group_concat

 SqlServer  对分组的内容进行拼接：

方案1：xml 子集,性能较差

方案2：借助 sqlCLR 接入。实现group_concat。性能完美，但是 阿里云的不支持！！！！

CREATE TABLE [dbo].[a_data_test](
[empid] [INT] NULL,
[workdate] [DATETIME] NULL
) ON [PRIMARY]

INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (1, '2018-8-17 10:20:43.33310:');
GO
INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (1, '2018-8-17 10:20:43.333');
GO
INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (2, '2018-8-17 10:21:09.29310:');
GO
INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (2, '2018-8-17 10:21:09.293');
GO
INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (3, '2018-8-17 10:21:37.87710:');
GO
INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (3, '2018-8-17 10:21:37.880');
GO
INSERT INTO [a_data_test] ([empid], [workdate]) VALUES (3, '2018-8-17 10:21:37.88010:');
GO

 1:

SELECT
ta.empid,
 STUFF((SELECT ',' +CONVERT(varchar(100), b.workdate, 25) 
                         FROM a_data_test b
                         WHERE ta.empid=b.empid
                         FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 1, '')
FROM 
(
SELECT 
a.empid
 FROM
dbo.a_data_test a
GROUP BY a.empid
) ta
--LEFT JOIN dbo.a_data_test b ON b.empid = ta.empid

　　

2： 

 https://archive.codeplex.com/?p=groupconcat
https://github.com/orlando-colamatteo/ms-sql-server-group-concat-sqlclr/tree/master/GroupConcat 

https://www.codeproject.com/Articles/691102/String-Aggregation-in-the-World-of-SQL-Server

https://www.anexinet.com/blog/group_concat-functionality-for-sql-server/