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orAClE中两张表A,B;AB有一相同字段,如何判断A的...

select * from t1 where exists(select 1 from T2 where T1.name = T2.name and T1.time > T2.Time1 and T1.time < T2.time2) 试一下,不知道对不对

两列的值不一样也没关系吗,如果这样,在C1中输入=COUNTA(A1,B1),然后下拉

select distinct(AID) as ID from A union select distinct(BID) as ID from B

declare i int; j int; begin for i in 65..90 loop --得到字母A-Z,如果只需要Q后面的,把65换为82 insert into test (mapcode) values (chr(i)); end loop; for i in 65..90 loop for j in 65..90 loop insert into test (mapcode) values (ch...

使用 GREATEST 函数即可。 SQL> SELECT 2 GREATEST(1,3,5,7,9) A 3 FROM 4 dual; A---------- 9SQL> select greatest('aa', 'bb', 'cc') A 2 from dual;A--cc

你说的这个问题很简单,一般都是采用触发器来实现的。 具体实现方式,请参考一下触发器的使用方法。 一看就明白。

保留a,b,c的联接关系,分别求,用union汇总, select 'a' as tab_name, distinct a.id, count(distinct a.id) from a, b, c where a.id = b.id a.id= c.id group by distinct a.id union select 'b', distinct b.id, count(distinct b.id) from ...

select null AID,BID from b where b.bid not in (select bid from ab where aid='A1') union select AID,BID from ab where aid='A1'

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