Question

假设我在表中有3列--A，B和C.我想确保如果我在列A中插入一些值（比如说x），我就不能插入一个有B或C的元组等于x，即，对于所有元组，值x应对于列A保持唯一。

请注意，对于其他元组，可以在A中重复x。

我知道SQL中的UNIQUE子句，但这只是为了确保一个值只在特定列中出现一次。由于Oracle中的CHECK语句不允许子查询，我无法弄清楚如何实现它。

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

然后不允许这个另一个元组的条目 -

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

另一方面，这个没问题（是的，2名员工可以使用相同类型的相同号码）

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

Answer 1

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（doc）

，它可能会也可能不会起作用

Answer 2

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;
/

fiddle

SQL Oracle约束值在多列之间是唯一的

2 个答案: