SQL 在 postgresql 上将默认值设置为 null
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set default value to null on postgresql
提问by 1252748
I read herethat I should be able to set the default value of a column like this:
我在这里读到我应该能够像这样设置列的默认值：
ALTER [ COLUMN ] column SET DEFAULT expression
But this:
但是这个：
ALTER address.IsActive SET DEFAULT NULL
Gives me this error:
给我这个错误：
ERROR: syntax error at or near "address" LINE 1: ALTER address.IsActive SET DEFAULT NULL
错误：“地址”处或附近的语法错误第 1 行：ALTER address.IsActive SET DEFAULT NULL
What have I done wrong? Also, how can I specify multiple columns to have their default value be NULL?
我做错了什么？另外，如何指定多个列以使其默认值为NULL？
采纳答案by álvaro González
You're not running the complete statement. You're missing the ALTER TABLEpart:
你没有运行完整的语句。你错过了ALTER TABLE部分：
ALTER TABLE [ ONLY ] name [ * ] action [, ... ] ALTER TABLE [ ONLY ] name [ * ] RENAME [ COLUMN ] column TO new_column ALTER TABLE name RENAME TO new_namewhere action is one of:
[...]
ALTER TABLE [ ONLY ] name [ * ] action [, ... ] ALTER TABLE [ ONLY ] name [ * ] RENAME [ COLUMN ] column TO new_column ALTER TABLE name RENAME TO new_name其中动作是以下之一：
[...]
回答by a_horse_with_no_name
The correct syntax is:
正确的语法是：
ALTER TABLE table_name ALTER COLUMN column_name SET DEFAULT NULL;
For several columns you repeat the ALTER COLUMNpart as documented in the manual:
对于多个列，您可以ALTER COLUMN按照手册中的说明重复该部分：
ALTER TABLE table_name
ALTER COLUMN foo SET DEFAULT NULL,
ALTER COLUMN bar SET DEFAULT 0;
回答by Pandian
Try like below... it will work....
像下面这样尝试......它会起作用......
ALTER TABLE address ALTER COLUMN IsActive SET DEFAULT NULL
回答by Tim
alter table dogs
alter column breed set default 'boxer'
alter table dogs
alter column breed set default null
