select distinct(name),count(name) num from t_col_desc group by name; name num
a 1
b 2
c 3 select name,num from t_tbl_desc; name num
a
b
c 以上是select出来的两张数据表,结构与字段都一样,都只有两个字段,name,num ,两张表name字段值相同, 其中一个表num字段没有值,将令一个表中的num字段中的值批量更新到没有值的字段中,怎么做?
a 1
b 2
c 3 select name,num from t_tbl_desc; name num
a
b
c 以上是select出来的两张数据表,结构与字段都一样,都只有两个字段,name,num ,两张表name字段值相同, 其中一个表num字段没有值,将令一个表中的num字段中的值批量更新到没有值的字段中,怎么做?
set num=b.name
from t_tbl_desc a ,
(
select name,count(name) num from t_col_desc group by name
)b
where a.name=b.name
t_tbl_desc
set
num=b.num
from
t_tbl_desc a,
(select distinct(name) as name,count(name) num from t_col_desc group by name)b
where
a.name=b.name
没必要发2遍