基于另一列的列的约束

Question

+----+-------+------+-----------+
| ID | Col1  | Col2 |   Col3    |
+----+-------+------+-----------+
|  1 | "One" |    0 | "Yeah"    |
|  2 | "One" |    0 | "Meh"     |
|  3 | "One" |    0 | "Why Not" |
|  4 | "Two" |    1 | "Huh"!    |
+----+-------+------+-----------+

而不是

+----+-------+------+-----------+
| ID | Col1  | Col2 |   Col3    |
+----+-------+------+-----------+
|  1 | "One" |    0 | "Yeah"    |
|  2 | "One" |    0 | "Meh"     |
|  3 | "One" |    1 | "Why Not" | (Normally it must be 0 or line 1 and 2 
|  4 | "Two" |    1 | "Huh"!    | Must be "1" )
+----+-------+------+-----------+

Answer 1

即使MySQL支持check约束，您也不会使用check约束来实现这一点。我认为最好的方法是使用外键约束。

您需要第二个表，其中包含有效的col1/col2值：

create table Col1Col2 as (
    col1 varchar(255) not null primary key,
    col2 int not null,
    unique (col1, col2)  -- this is not strictly necessary see below
);

那么你的桌子应该是：

create table t as (
    id int auto_increment primary key,
    col1 varchar(255) not null,
    col2 int not null
    col3 int,
    constraint fk_t_col1_col2 foreign key (col1, col2) references col1col2(col1, col2)
);