状态缩写检查约束

Question

I want to create a check constraint for state abbreviations. I only want to allow a two character insert for the State column. What would be the code? my code was: State VARCHAR(2) NOT NULL CONSTRAINT CK_StateAbbr CHECK (State like 'xx')

I am assuming putting the xx in there will only allow xx for the state. Would I put CHECK (State like '[AZ][AZ]')?

Answer 1

With most versions of MySQL, it makes no difference. A check constraint is accepted as syntax, but it is not implemented.

That leaves you with several choices. First, ignore the issue. This would be the most common approach. Second, use a trigger. That makes for messy code and is not optimal.

The third approach is to create a table with all valid state abbreviations. Then you can use a foreign key constraint, to ensure that the value is valid.