Unique value Constraint with multiple columns across table，不是Oracle中的组合

Question

在 oracle 中有没有办法强制两列之间的唯一性？

它不是两列组合之间的唯一性，而是两列之间 table 的值。

参考文献：

不应允许的示例数据：

id | phone1 | phone2
1  | 111    | 111

id | phone1 | phone2
1  | 111    | NULL
2  | 111    | NULL  

id | phone1 | phone2
1  | 111    | NULL
2  | NULL   | 111

我的 Oracle 版本：

Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

Answer 1

我会结合检查约束和函数的唯一索引来解决它：

CREATE TABLE t(id NUMBER, phone1 NUMBER, phone2 NUMBER);
ALTER  TABLE t ADD CONSTRAINT c1 CHECK (phone1 <> phone2);
CREATE UNIQUE INDEX u ON t(COALESCE(phone1, phone2));

案例 1 有效：

INSERT INTO t VALUES (1, 111, 111);
ORA-02290: check constraint (C1) violated

案例 2 也适用：

INSERT INTO t VALUES (1, 111, NULL);
INSERT INTO t VALUES (2, 111, NULL);
ORA-00001: unique constraint (U) violated

案例三，还有：

INSERT INTO t VALUES (1, 111, NULL);
INSERT INTO t VALUES (2, NULL, 111);
ORA-00001: unique constraint (WFL.U) violated

然而，这不受保护：

INSERT INTO t VALUES (1, 111, 222);
INSERT INTO t VALUES (2, 222, 111);

Answer 2

我会使用 check() 约束来确保每一行的唯一性，以及跨行唯一性的唯一索引：

create table mytable (
    id int, 
    phone1 int, 
    phone2 int,
    check (phone1 <> phone2)
);

create unique index myidx on mytable(
    greatest(coalesce(phone1, phone2), coalesce(phone2, phone1)),
    least(coalesce(phone1, phone2), coalesce(phone2, phone1))
);

这种方法的好处是它还可以防止插入像 (111, 222) 和 (222, 111) 这样的元组。

Demo on DB Fiddle:

insert into mytable values(1, 111, 111);

ORA-02290: check constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.SYS_C0020876) violated

begin
    insert into mytable values(1, 111, null);
    insert into mytable values(1, 111, null);
end;
/

ORA-00001: unique constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.MYIDX) violated
ORA-06512: at line 3

begin
    insert into mytable values(1, 111, null);
    insert into mytable values(1, null, 111);
end;
/

ORA-00001: unique constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.MYIDX) violated
ORA-06512: at line 3

begin
    insert into mytable values(1, 111, 222);
    insert into mytable values(1, 222, 111);
end;
/

ORA-00001: unique constraint (FIDDLE_SMBYKTEIHNNVOHKZSCYK.MYIDX) violated
ORA-06512: at line 3

Unique value Constraint with multiple columns across table，不是Oracle中的组合

Unique value Constraint with multiple columns across the table, not the combination in Oracle

sql

oracle

unique-constraint

multiple-columns