设置JSON列的默认值 [英] Setting default value for a json column
问题描述
我正在研究使用Postgres通过activerecords将json设置为列的功能 json处理功能我想知道如何在创建表时给它一个默认值,例如 {name:``,other_name:''}
等等...
I am looking at using Postgres's feature of setting json into a column via activerecords json handling features I am wondering how I would give it a default value upon table creation of something like {name: '', other_name: ''}
and so on ...
我还希望了解如何为列创建默认的json值,例如上面的示例,然后再填充值,但是在
I am also looking to understand how if I create a default json value for a column, like the example above and then later on I fill in the values, but then at a some other time reset it back to "default" how that would look.
推荐答案
就像其他默认设置一样,一旦修复,就可以将其重置为默认外观。 JSON语法:
It's just like any other default, once you fix up the json syntax:
CREATE TABLE mytable (
someothercol integer,
somecol json DEFAULT '{"name": "", "other_name": ""}'
);
如果设置为 DEFAULT
,只是这样:
If you set to DEFAULT
, it does just that:
regress=> INSERT INTO mytable(someothercol, somecol) VALUES (42, '{"nondefault": 1}');
INSERT 0 1
regress=> SELECT * FROM mytable;
someothercol | somecol
--------------+-------------------
42 | {"nondefault": 1}
(1 row)
regress=> UPDATE mytable SET somecol = DEFAULT WHERE someothercol = 42;
UPDATE 1
regress=> SELECT * FROM mytable;
someothercol | somecol
--------------+--------------------------------
42 | {"name": "", "other_name": ""}
(1 row)
这篇关于设置JSON列的默认值的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!