数据仓库服务 GaussDB(DWS)-枚举类型:枚举类型的安全性

时间：2025-02-12 15:04:42

枚举类型的安全性

每一种枚举数据类型都是独立的并且不能和其他枚举类型相比较。

  
       CREATE TYPE happiness AS ENUM ('happy', 'very happy', 'ecstatic');CREATE TABLE holidays (num_weeks integer, happiness happiness);INSERT INTO holidays(num_weeks,happiness) VALUES (4, 'happy');INSERT INTO holidays(num_weeks,happiness) VALUES (6, 'very happy');INSERT INTO holidays(num_weeks,happiness) VALUES (8, 'ecstatic');INSERT INTO holidays(num_weeks,happiness) VALUES (2, 'sad');ERROR:  invalid input value for enum happiness: "sad"SELECT person.name, holidays.num_weeks FROM person, holidays       WHERE person.current_mood = holidays.happiness;ERROR:  operator does not exist: mood = happiness

如果需要作比较，可以使用自定义的操作符或者在查询中加上显式类型：

  
        SELECT person.name, holidays.num_weeks FROM person, holidays       WHERE person.current_mood::text = holidays.happiness::text; name | num_weeks------+----------- Moe  |         4(1 row)