PostgreSQL 检查约束

Question

CREATE TABLE my_table
(
    fk      INTEGER,
    field_1 INTEGER,
    field_2 INTEGER,
    field_3 INTEGER
)

VALID:

    fk    |    field_1    |    field_2    |    field_3              
----------+---------------+---------------+---------------
     1    |      1        |      null     |      null
     1    |      null     |      1        |      null
     1    |      null     |      null     |      1

是否可以创建检查约束，仅允许 3 个字段中的 1 个字段对于 1 个 fk 不为空？

Answer 1

想到的直接方法:

CHECK ((field_1 IS NOT NULL AND field_2 IS NULL AND field_3 IS NULL) OR
       (field_2 IS NOT NULL AND field_1 IS NULL AND field_3 IS NULL) OR
       (field_3 IS NOT NULL AND field_1 IS NULL AND field_2 IS NULL))