更改列類型爲timestamp

Question

我有一個是這樣定義的表：

CREATE TABLE session_requests 
(
    id character varying(255) NOT NULL, 
    authorization_enc character varying(255), 
    auto_close integer, 
    date_created character varying(255) DEFAULT '1970-01-01 01:00:00'::character varying,, 
.... 
) 

我試圖做

alter table session_requests alter column date_created type timestamp using date_created::timestamp; 

是我得到的錯誤是

ERROR: default for column "date_created" cannot be cast automatically to type timestamp 

任何人有任何建議嗎？

Answer 1

在一次交易中完成。你甚至可以做一個single statement：

ALTER TABLE session_requests 
    ALTER date_created DROP DEFAULT 
,ALTER date_created type timestamp USING date_created::timestamp 
,ALTER date_created SET DEFAULT '1970-01-01 01:00:00'::timestamp; 

SQL Fiddle.

旁白：character varying(255)幾乎總是在Postgres的一個壞的（毫無意義）的選擇。更多：

• Refactor foreign key to fields