create table company
(
id int identity primary key,
names nvarchar(20)
)
insert into company(names) values('中部印刷网')
insert into company(names) values('睿智软件')
go
create table job
(
id int identity primary key,
jobName nvarchar(20),
companyName nvarchar(20),
companyId int
)
go
insert into job(jobName,companyName,companyId) values('程序员','中部印刷网',null)
insert into job(jobName,companyName,companyId) values('美工','中部印刷网',null)
insert into job(jobName,companyName,companyId) values('软件工程师','睿智软件',null)
go

--1
update job set companyId = (select id from company where names = t.companyName) from job t

--2
update job set companyId = m.id 
from job t , company m where t.companyName = m.names

select * from job
/*
id          jobName              companyName          companyId   
----------- -------------------- -------------------- ----------- 
1           程序员                  中部印刷网                1
2           美工                   中部印刷网                1
3           软件工程师                睿智软件                 2

（所影响的行数为 3 行）
*/

drop table company , job

------解决方案--------------------

SQL code


alter table job add company_id varchar(10) default null

update b set b.company_id=a.id 
  from job b,company a 
    where b.companyName=a.names