在postgresql中添加一个二分之一的非空约束

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)
);

我需要创建一个约束,以便schoolName或者studiedAt不需要为null(其中一个必须包含信息).

我该怎么做呢？

Answer 1

您可以使用检查约束,例如

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

从手册:

检查约束是最通用的约束类型.它允许您指定某列中的值必须满足布尔(真值)表达式.

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))