create cursor b1 (jnh n(1),mc c(3))
insert into b1 values (1,"ab")
insert into b1 values (2,"abc")
insert into b1 values (3,"ac")
insert into b1 values (4,"bc")
insert into b1 values (5,"A5")

create cursor b2 (jnh n(1),mc c(2))
insert into b2 values (1,"ab")
insert into b2 values (2,"aba")
insert into b2 values (3,"a")

查两表mc中完全相同的记录。
SELECT * FROM b1 WHERE ALLTRIM(mc) in (SELECT ALLTRIM(mc) FROM b2)
这个查法不行，应如何进行？谢谢！

select * from b1,b2 where alltrim(b1.mc)==alltrim(b2.mc)

select * from b1 inner join b2 on alltrim(b1.mc)==alltrim(b2.mc)

create cursor b2 (jnh n(1),mc c(2))
insert into b2 values (2,"aba")
这个mc数据"aba"会丢失"a"

[此贴子已经被作者于2021-11-21 21:00编辑过]

是我把宽度写错了

谢谢以上各位了！！！

两位版主，查询出来是两表连接表，如何只出现一个表?
特别是对查不相同时很重要。
谢谢！

[此贴子已经被作者于2021-11-22 09:13编辑过]

选择想要的字段就可以

create cursor b1 (jnh n(1),mc c(3))
insert into b1 values (1,"ab")
insert into b1 values (2,"abc")
insert into b1 values (3,"ac")
insert into b1 values (4,"bc")
insert into b1 values (5,"A5")

create cursor b2 (jnh n(1),mc c(3))
insert into b2 values (1,"ab")
insert into b2 values (2,"aba")
insert into b2 values (3,"a")

select b1.jnh,b1.mc from b1,b2 where b1.mc==b2.mc

查两表全部
select * from b1,b2 where alltrim(b1.mc)==alltrim(b2.mc)

查相同的b1
select b1.* from b1,b2 where alltrim(b1.mc)==alltrim(b2.mc)

查相同的b2
select b2.* from b1,b2 where alltrim(b1.mc)==alltrim(b2.mc)

b1有b2没有
select * from b1 where mc not in (select mc from b2)

b2有b1没有
select * from b2 where mc not in (select mc from b1)

多谢！！！