PostgreSQL怎么更改列类型

PostgreSQL怎么更改列类型

我们来看一下pg中的语法：

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highgo=# \h auto
where action is one of:
    ADD [ COLUMN ] [ IF NOT EXISTS ] column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ]
    DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ]
    ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
    ALTER [ COLUMN ] column_name SET DEFAULT expression

更改列类型demo:

highgo=# alter table p1 alter COLUMN pswd type text ;
ALTER TABLE
highgo=# \d p1
                           Table "public.p1"
 Column |            Type             | Collation | Nullable | Default 
--------+-----------------------------+-----------+----------+---------
 id     | integer                     |           |          | 
 pswd   | text                        |           |          | 
 time   | timestamp without time zone |           |          |

请注意，假如是不同类型转换的话可能不成功。

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