更新数据库字段
1 用a表中的字段去更新b表中的字段
create table student
(
student_id
int
not
null
,student_name varchar(
30
) not
null
,city_code varchar(
10
)
null
,city_name varchar(
50
)
null
);
create table city
(
code varchar(
10
) not
null
,name varchar(
50
) not
null
);
insert into student values(
1
,
'john'
,
'001'
,
null
);
insert into student values(
2
,
'nick'
,
'002'
,
null
);
insert into city values(
'001'
,
'beijing'
);
insert into city values(
'002'
,
'shanghai'
);
insert into city values(
'003'
,
'shenzhen'
);
有两个表：student & city，现在需要取出 city.name 来更新 student.city_name。两表关联条件是 student.city_code=city.code。
update student s, city c
set s.city_name = c.name
where s.city_code = c.code;
也可以试下面的相关子查询：
update student s set city_name = (select name from city where code = s.city_code);
2 用同一张表的A字段更新B字段
UPDATE Baby_Info set createTime = editTime
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