postgresql 修改表结构，添加索引,postgresql索引要想删除，就要删除表

postgresql 修改表结构，添加索引,postgresql索引要想删除，就要删除表

玩了一下pgsql的修改表格的命令，感觉和mysql基本上差不多，唯有一些不同的是，alter 只能添加主键和外键，普通索引，唯一索引不能添加，还不能删除。要想删除，就要删除表，重建表。这个有点坑爹，我用的版本是8.1.13，非常低的版本了。不知道高版本有没有解决这个问题。

playboy=> alter table test add sex integer; //添加一个表字段
ALTER TABLE
playboy=> d test
Table "public.test"
Column | type | Modifiers
--------------+-----------------------+---------------------------------------------------
id | integer | not null default nextval('seq_test_id'::regclass)
name | character varying(32) |
date_created | date |
sex | integer |
Indexes:
"playboy_id_pk" PRIMARY KEY, btree (id)

playboy=> alter table test alter sex type varchar(1); //修改表字段类型
ALTER TABLE
playboy=> d test
Table "public.test"
Column | Type | Modifiers
--------------+-----------------------+---------------------------------------------------
id | integer | not null default nextval('seq_test_id'::regclass)
name | character varying(32) |
date_created | date |
sex | character varying(1) |
Indexes:
"playboy_id_pk" PRIMARY KEY, btree (id)

playboy=> create unique index unique_name on test(name); //创建唯一索引
CREATE INDEX
playboy=> d test
Table "public.test"
Column | Type | Modifiers
--------------+-----------------------+---------------------------------------------------
id | integer | not null default nextval('seq_test_id'::regclass)
name | character varying(32) |
date_created | date |
sex | character varying(1) |
Indexes:
"playboy_id_pk" PRIMARY KEY, btree (id)
"unique_name" UNIQUE, btree (name)

playboy=> alter table test rename sex to age; //表字段改名
ALTER TABLE
playboy=> d test
Table "public.test"
Column | Type | Modifiers
--------------+-----------------------+---------------------------------------------------
id | integer | not null default nextval('seq_test_id'::regclass)
name | character varying(32) |
date_created | date |
age | character varying(1) |
Indexes:
"playboy_id_pk" PRIMARY KEY, btree (id)
"unique_name" UNIQUE, btree (name)

playboy=> alter table test drop age; //删除表字段
ALTER TABLE