SQL根据第二张表字段值更新第一张表字段值

truncate table tab1

create table tab1
(
a int primary key not null identity(1,1),
b varchar(10),
c varchar(10),
d float,
e float,
f float
)
go

insert into tab1(b,c,d,e,f) values('a','aa',1,2,3);
insert into tab1(b,c,d,e,f) values('b','bb',2,3,4);
insert into tab1(b,c,d,e,f) values('c','cc',3,4,5);
insert into tab1(b,c,d,e,f) values('d','dd',4,5,6);
insert into tab1(b,c,d,e,f) values('e','ee',5,6,7);
go

select * from tab1;

--查询总分比平均分大的记录并按总分降序排列
select a,b,c,d,e,f,d+e+f as sumScore,(d+e+f)/3 as avgScore from tab1 where d+e+f>(d+e+f)/3 order by b,d+e+f desc;

--根据第二张表字段值更新第一张表字段值
--update 表一 set 表一.A = 表二.B from 表一,表二 where 表一.C = 表二.D
update tab1 set tab1.a=tab2.b from tab1,tab2 where tab1.c=tab2.d;