如何合并重复行然后删除所有重复后保持行

Question

我有表中有第15列我想合并重复行在一行，然后删除该重复行后保留一行作为记录

我的表像

id name email address city state country salary .... 
1 a a@a.a null null a  xyx null 
2 null a@a.a a  a  null null 10000 

Answer 1

你可以小组email和更新与GroupWise的最大所有列：

declare @t table (id int, name varchar(50), email varchar(50), 
    address varchar(50), city varchar(50), state varchar(50), 
    country varchar(50), salary int) 
insert @t 
values (1, 'a', 'a@a.a', null, null, 'a', 'xyx', null), 
     (2, null, 'a@a.a', 'a', 'a', null, null, 10000) 

-- Update all rows for an email address 
update t 
set  name = combined.name 
,  address = combined.address 
,  city = combined.city 
,  state = combined.state 
,  country = combined.country 
,  salary = combined.salary 
from @t t 
join (
     select 
       max(name) as name 
     ,  email 
     ,  max(address) as address 
     ,  max(city) as city 
     ,  max(state) as state 
     ,  max(country) as country 
     ,  max(salary) as salary 
     from @t 
     group by 
       email 
     ) combined 
on  combined.email = t.email 

然后删除所有杜褶行：

-- Delete duplicate rows 
delete t 
from @t t 
join @t t2 
on  t2.email = t.email 
     and t2.id < t.id 

-- Display result 
select * from @t 

此打印：

id name email address city state country salary 
1 a a@a.a a  a a  xyx  10000