Postgres SQL约束一个字符类型(Postgres SQL constraint a character type)

Postgres SQL约束一个字符类型(Postgres SQL constraint a character type)

我在Postgres中有一个表定义。 我想为一个Character数据类型的列添加一个约束，只有3个允许的值：

CREATE TABLE my_table ( id character varying(255) NOT NULL, uid character varying(255) NOT NULL, my_text text NOT NULL, is_enabled boolean NOT NULL );

所以我希望my_text列只包含'A'，'B'或'C'作为值。

我在哪里可以找到关于此的一些文档？

I have a table definition in Postgres. I would like to add a constraint to a column that is of Character datatype to have only 3 allowed values:

CREATE TABLE my_table ( id character varying(255) NOT NULL, uid character varying(255) NOT NULL, my_text text NOT NULL, is_enabled boolean NOT NULL );

So I want the my_text column to contain only 'A', 'B' or 'C' as values.

Where can I find some documentation on this?

最满意答案

使用检查约束：

CREATE TABLE my_table ( id character varying(255) NOT NULL, uid character varying(255) NOT NULL, my_text text NOT NULL, is_enabled boolean NOT NULL, constraint check_allowed check (my_text in ('A', 'B', 'C')) );

手册中的更多细节： http ： //www.postgresql.org/docs/current/static/ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS

Use a check constraint:

CREATE TABLE my_table ( id character varying(255) NOT NULL, uid character varying(255) NOT NULL, my_text text NOT NULL, is_enabled boolean NOT NULL, constraint check_allowed check (my_text in ('A', 'B', 'C')) );

More details in the manual: http://www.postgresql.org/docs/current/static/ddl-constraints.html#DDL-CONSTRAINTS-CHECK-CONSTRAINTS