![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
CREATE DATABASE T
create table A
(
ID int,
UserName nvarchar(50)
)
create table B
(
ID int,
UserDisplayName nvarchar(50)
)
insert into A values(1,'USER1');
insert into A values(2,'USER2');
insert into A values(3,'USER3');
insert into B values(1,'Display1');
insert into B values(2,'Display2');
insert into B values(3,'Display3');
insert into B values(4,'Display4')
update A set A.UserName = B.UserDisplayName from A,B where A.ID = B.ID
效果如图所示: