如何大量修改关联数据并删除重复数据

建议你在用户表加个字段，将用一个id的用户归并成同一个用户code，比如：

if object_id('tempdb..#user') is not null drop table #user
if object_id('tempdb..#DAT') is not null drop table #DAT
create table #user(id VARCHAR(10),code VARCHAR(10),u_name NVARCHAR(10),CreatedDate DATETIME)
insert into #user
select 'A_111','1514',N'A','20170731' union all
select 'A_111','1314',N'A','20170730' union all
select 'A_111','1111',N'A','20170718' union all
select 'A_222','1320',N'B','20170718' union all
select 'A_333','1450',N'C','20170718' union all
select 'A_333','1350',N'C','20170719'
CREATE TABLE #DAT(id INT,DAT VARCHAR(100),UserCode VARCHAR(10),CreatedDate DATETIME)
insert into #DAT
select 1,'AAA','1514','20170730' union all
select 2,'SSS','1314','20170729' union all
select 3,'BBB','1111','20170728' union all
select 4,'QQQ','1111','20170727' union all
select 5,'WWW','1320','20170726' union all
select 6,'EEE','1320','20170725' union all
select 7,'RRR','1450','20170724' union all
select 8,'TTT','1350','20170723' 
select * from #DAT
if col_length('tempdb..#USER','AKA_Code') IS NULL
alter table #USER add AKA_Code varchar(10)
update u set u.AKA_Code=u.aka from (
   SELECT *,min(code)over(partition by id) as aka FROM #USER 
) as u 
select * from #user
update d set d.UserCode=u.AKA_Code
from #DAT as d inner join #user as u on d.UserCode=u.code
where d.UserCode!=u.AKA_Code
select * from #DAT