为什么无符号整数在PostgreSQL中不可用？ [英] Why unsigned integer is not available in PostgreSQL?

问题描述

我碰到了这篇文章（ MySQL中的tinyint，smallint，mediumint，bigint和int之间有什么区别？），并意识到PostgreSQL不支持无符号整数。

I came across this post (What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL?) and realized that PostgreSQL does not support unsigned integer.

在大多数情况下，我在MySQL中使用无符号整数作为自动递增的主键。在这种设计中，当我将数据库从MySQL移植到PostgreSQL时，该如何克服？

Most of the time, I use unsigned integer as auto incremented primary key in MySQL. In such design, how can I overcome this when I port my database from MySQL to PostgreSQL?

谢谢。

推荐答案

已经回答了为什么postgresql缺少无符号类型的问题。但是我建议对无符号类型使用域。

It is already answered why postgresql lacks unsigned types. However I would suggest to use domains for unsigned types.

http://www.postgresql.org/docs/9.4/static/sql-createdomain.html

 CREATE DOMAIN name [ AS ] data_type
    [ COLLATE collation ]
    [ DEFAULT expression ]
    [ constraint [ ... ] ]
 where constraint is:
 [ CONSTRAINT constraint_name ]
 { NOT NULL | NULL | CHECK (expression) }

域就像一个类型，但有附加约束。

Domain is like a type but with an additional constraint.

举一个具体的例子，您可以使用

For an concrete example you could use

CREATE DOMAIN uint2 AS int4
   CHECK(VALUE >= 0 AND VALUE < 65536);

当我尝试滥用该类型时，这是psql给出的。

Here is what psql gives when I try to abuse the type.

DS1 =＃select（346346 :: uint2）;

DS1=# select (346346 :: uint2);

错误：域uint2的值违反了检查约束 uint2_check

ERROR: value for domain uint2 violates check constraint "uint2_check"

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