sql - 在 postgresql 中添加二选一非空约束

Question

如果我在 Postgresql 中有一个表:

create table Education ( 
    id                  integer references Profiles(id),
    finished            YearValue not null,
    started             YearValue,
    qualification       text,
    schoolName          text,
    studiedAt           integer references Organizations(id),
    primary key (id)
);

我需要进行约束，以便 schoolName 或 studiedAt 不能为 null(其中之一必须包含信息)。

我该怎么做？

Answer 1

您可以使用 check constraint例如

constraint chk_education check (schoolName is not null or studiedAt is not null)

来自手册:

A check constraint is the most generic constraint type. It allows you to specify that the value in a certain column must satisfy a Boolean (truth-value) expression.

编辑:符合 Pithyless 解释的替代方案:

constraint chk_education check ((schoolName is not null and studiedAt is null) or (schoolName is null and studiedAt is not null))