SQL PostgreSQL 9.1 主键自增
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PostgreSQL 9.1 primary key autoincrement
提问by WildDev
I'm trying to add a primary key with an autoincrement.
我正在尝试使用自动增量添加主键。
I have read some docs and other questions - there're SERIALand nextval()statements but it doesn't work.
我已经阅读了一些文档和其他问题 - 有SERIAL和nextval()陈述，但它不起作用。
Here's what I made:
这是我做的：
CREATE TABLE IF NOT EXISTS "category" (
"id" integer SERIAL PRIMARY KEY,
"name" varchar(30) DEFAULT NULL
); // the error near "SERIAL"
and
和
CREATE SEQUENCE your_seq;
CREATE TABLE IF NOT EXISTS "category" (
"id" integer PRIMARY KEY nextval('your_seq'),
"name" varchar(30) DEFAULT NULL
); // the error near 'nextval'
What do I wrong? I just want to increment the primary key by 1.
我怎么了？我只想将主键加 1。
回答by mu is too short
serialis, more or less, a column type so saying integer serialis like saying text text, just say serial:
serial或多或少是一种列类型，所以说integer serial就像说text text，只需说serial：
CREATE TABLE IF NOT EXISTS "category" (
"id" SERIAL PRIMARY KEY,
"name" varchar(30) DEFAULT NULL
);
If you want to create the sequence yourself then you want to make the default value of idthe next value in the sequence and that means saying default nextval('your_seq'):
如果您想自己创建序列，那么您希望将序列中id的下一个值设为默认值，这意味着default nextval('your_seq')：
CREATE SEQUENCE your_seq;
CREATE TABLE IF NOT EXISTS "category" (
"id" integer PRIMARY KEY default nextval('your_seq'),
"name" varchar(30) DEFAULT NULL
);
To simulate the usual serialbehavior you'll also want to make the sequence owned by the table:
要模拟通常的serial行为，您还需要使表拥有序列：
alter sequence your_seq owned by category.id;
Reading the Serial Typessection of the manual might be fruitful.
阅读手册的串行类型部分可能会很有成效。
I'd also recommend that you don't double quote your table and column names unless you have to. PostgreSQL will fold your identifiers to lower case so idand "id"will be the same thing but unnecessary quoting is a bad habit that can easily lead to a big mess of quotes everywhere.
我还建议你不要双引号你的表和列名，除非你必须。PostgreSQL将折叠的标识符以小写因此id而"id"将是相同的事情，但不必要的报价是一个坏习惯，很容易导致行情的大混乱无处不在。
回答by Valentin Podkamennyi
If someone needs to modify an existing table to add a primary key with auto-increment:
如果有人需要修改现有表以添加具有自动增量的主键：
ALTER TABLE table_name ADD COLUMN pk_column_name SERIAL PRIMARY KEY;
