如何在SQL中合并约束CHECK？

Question

下面有一个table：

CREATE TABLE LectureHalls
(
id SERIAL PRIMARY KEY,
floor INTEGER CHECK (floor <= 4),
classroom INTEGER NOT NULL,
CONSTRAINT sc_unique_lectureHall UNIQUE (id, floor, classroom),
CONSTRAINT sc_unique_lectureHall2 UNIQUE (floor, classroom);
);

是否可以在 sql 中创建这样的约束，以便当 floor = 1 classroom> 0 且 classroom <= 30 时？

Answer 1

这是你想要的吗？

create table lecturehalls (
    id serial primary key,
    floor integer check (floor <= 4),
    classroom integer not null,
    unique (floor, classroom),
    check(floor is distinct from 1 or (classroom > 0 and classroom <= 30))
);

请注意，我删除了 (id, floor, classroom) 上的唯一约束：id 是 table 的主键，因此无论如何这是一个 no-op。

Answer 2

您可以：

CREATE TABLE LectureHalls
(
id SERIAL PRIMARY KEY,
floor INTEGER NOT NULL CHECK (floor BETWEEN 1 AND 4),
classroom INTEGER NOT NULL,
UNIQUE KEY (floor, classroom),
CHECK (floor = 1 AND classroom BETWEEN 1 AND 30) 
);

此表格允许扩展到更多楼层：

CREATE TABLE LectureHalls
(
id SERIAL PRIMARY KEY,
floor INTEGER NOT NULL CHECK (floor BETWEEN 1 AND 4),
classroom INTEGER NOT NULL,
UNIQUE KEY (floor, classroom),
CHECK (floor = 1 AND classroom BETWEEN 1 AND 30 OR
       floor = 2 AND classroom BETWEEN 1 AND 15 OR
       floor = 3 AND classroom BETWEEN 1 and 24) 
);

如何在SQL中合并约束CHECK？

How to combine constraint CHECK in SQL?

sql

postgresql

check-constraints

create-table