Question

我想将一列数据从文本更改为类型时间戳。我的数据中没有时区。我的数据格式如28-03-17 17:22，包括时间和日期，但没有时区。换句话说，我的所有数据都在同一时区。我该怎么做？

我在下面尝试了多种方法，但我仍然找不到合适的方法。希望你能帮帮我。

当然，如果我的麻烦得以解决，我可以建立一个新的桌子。

alter table AB
alter create_time type TIMESTAMP;

ERROR:  column "create_time" cannot be cast automatically to type timestamp without time zone
HINT:  You might need to specify "USING create_time::timestamp without time zone".
********** Error **********

ERROR: column "create_time" cannot be cast automatically to type timestamp without time zone
SQL state: 42804
Hint: You might need to specify "USING create_time::timestamp without time zone".

alter table AB
alter create_time type TIMESTAMP without time zone;

ERROR:  column "create_time" cannot be cast automatically to type timestamp without time zone
HINT:  You might need to specify "USING create_time::timestamp without time zone".
********** Error **********

ERROR: column "create_time" cannot be cast automatically to type timestamp without time zone
SQL state: 42804
Hint: You might need to specify "USING create_time::timestamp without time zone".

alter table AB
alter create_time::without time zone type TIMESTAMP;

ERROR:  syntax error at or near "::"
LINE 2:  alter create_time::without time zone type TIMESTAM
                          ^
********** Error **********

ERROR: syntax error at or near "::"
SQL state: 42601
Character: 50

alter table AB
alter create_time UTC type TIMESTAMP;

ERROR:  syntax error at or near "UTC"
LINE 2: alter create_time UTC type TIMESTAMP;
                          ^
********** Error **********

ERROR: syntax error at or near "UTC"
SQL state: 42601
Character: 50

Answer 1

USING...出现在类型：

之后

... alter create_time type TIMESTAMP USING create_time::TIMESTAMP;

Answer 2

如果create_time的TEXT类型具有有效的日期值，则更容易按如下方式继续进行更改（建议首先将表转储作为备份）：

-- Create a temporary TIMESTAMP column
ALTER TABLE AB ADD COLUMN create_time_holder TIMESTAMP without time zone NULL;

-- Copy casted value over to the temporary column
UPDATE AB SET create_time_holder = create_time::TIMESTAMP;

-- Modify original column using the temporary column
ALTER TABLE AB ALTER COLUMN create_time TYPE TIMESTAMP without time zone USING create_time_holder;

-- Drop the temporary column (after examining altered column values)
ALTER TABLE AB DROP COLUMN create_time_holder;

Answer 3

您没有指定create_time的原始类型，因此我假设它是带时区的TIME（因为DATE类型或带有时区的TIMESTAMP在尝试更改为没有时区的TIMESTAMP时不应该给出所述错误）。由于TIMESTAMP除了TIME之外还有日期信息，因此您需要在ALTER语句中补充日期信息，例如：

ALTER TABLE AB ALTER COLUMN create_time TYPE TIMESTAMP without time zone USING date('20170327') + create_time;

如果你有一个相应的DATE列（比如create_date），你可以将它传递给date（）函数，如：

ALTER TABLE AB ALTER COLUMN create_time TYPE TIMESTAMP without time zone USING date(create_date) + create_time;

Answer 4

用于将列的数据类型从bigint更改为时间戳（对于纪元到时间戳）

alter table <tablename> alter column <columnname> type timestamp without time zone using to_timestamp(<columnname>) AT TIME ZONE 'UTC';

例如;

alter table AB alter column col type timestamp without time zone using to_timestamp(col) AT TIME ZONE 'UTC';

用于将列的数据类型从timestamp更改为bigint（用于时间戳到纪元）

alter table <tablename> alter column <columnname> type bigint using extract(EPOCH from <columnname>);

例如;

alter table AB alter column col type bigint using extract(EPOCH from col);

postgreSQL将列数据类型更改为没有时区的时间戳

4 个答案: