7

假设我在一个表中有 3 列 - A、B 和 C。我想确保如果我在 A 列中插入一些值（比如 x），我不能插入 B 或 C 等于 x 的元组，即对于所有元组，值 x 对于列 A 应保持唯一。

请注意，对于其他一些元组，x 可以在 A 中重复。

我知道 SQL 中的 UNIQUE 子句，但这只是为了确保一个值在特定列中只出现一次。由于 Oracle 中的 CHECK 语句不允许子查询，我不知道如何实现这一点。

编辑（添加更多信息）

主键是 Employee_Number，而有问题的 3 列是 LandlineNo、MobileNo 和 VOIP。因此假设这是一个条目：

Employee_Number = 1, LandlineNo = x, MobileNo = y, VOIP = z

然后不允许另一个元组的这个条目 -

Employee_Number = 2, LandlineNo = a, MobileNo = x, VOIP = c

另一方面，这个就可以了（是的，2名员工可以拥有相同数量的相同类型）

Employee_Number = 2, LandlineNo = x, MobileNo = b, VOIP = c
4

2 回答 2

2 
CREATE MATERIALIZED VIEW mv_my
BUILD IMMEDIATE
REFRESH FAST ON COMMIT AS
SELECT DISTINCT
    CASE 
        WHEN t2.Employee_Number IS NOT NULL THEN 1
        WHEN t3.Employee_Number IS NOT NULL THEN 1
        WHEN t4.Employee_Number IS NOT NULL THEN 1
        ELSE 0
    END AS wrong
FROM table t1
    LEFT JOIN table t2 ON t2.MobileNo = t1.LandlineNo AND t2.Employee_Number != t1.Employee_Number
    LEFT JOIN table t3 ON t3.VOIP = t1.LandlineNo AND t3.Employee_Number != t1.Employee_Number
    LEFT JOIN table t4 ON t4.VOIP = t1.MobileNo AND t4.Employee_Number != t1.Employee_Number
/

ALTER TABLE mv_my ADD CHECK(wrong = 0)
/

根据您的 oracle 版本（文档） ，它可能有效也可能无效

于 2013-11-02T18:41:53.317 回答
1 
create table table1(
   a varchar2(20) not null,
   b varchar2(20) not null,
   c varchar2(20) not null
)
/
create table ctrs (
   val varchar2(20) unique,
   ctr_a int,
   ctr_b int,
   ctr_c int,
   check(ctr_a*ctr_b+ctr_a*ctr_c+ctr_b*ctr_c=0)
)
/
create trigger table1_trg 
before insert or update or delete on table1
for each row
begin
   if deleting then 
      update ctrs set ctr_a = ctr_a - 1 where val = :old.a;
      update ctrs set ctr_b = ctr_b - 1 where val = :old.b;
      update ctrs set ctr_c = ctr_c - 1 where val = :old.c;
   elsif inserting then
      merge into ctrs using (
        select :new.a as x from dual union all
        select :new.b as x from dual union all
        select :new.c as x from dual
      )
      on (val = x)
      when not matched then 
         insert (val, ctr_a, ctr_b, ctr_c) values (x, 0, 0, 0);
      update ctrs set ctr_a = ctr_a + 1 where val = :new.a;
      update ctrs set ctr_b = ctr_b + 1 where val = :new.b;
      update ctrs set ctr_c = ctr_c + 1 where val = :new.c;
   else
      update ctrs set ctr_a = ctr_a - 1 where val = :old.a;
      update ctrs set ctr_b = ctr_b - 1 where val = :old.b;
      update ctrs set ctr_c = ctr_c - 1 where val = :old.c;
      merge into ctrs using (
        select :new.a as x from dual union all
        select :new.b as x from dual union all
        select :new.c as x from dual
      )
      on (val = x)
      when not matched then 
         insert (val, ctr_a, ctr_b, ctr_c) values (x, 0, 0, 0);
      update ctrs set ctr_a = ctr_a + 1 where val = :new.a;
      update ctrs set ctr_b = ctr_b + 1 where val = :new.b;
      update ctrs set ctr_c = ctr_c + 1 where val = :new.c;
   end if;
end;
/

小提琴

于 2013-11-02T17:53:40.193 回答