app.get('/gauthServer',function(req,res) {
        console.log(req.cookies.currentUserEmail);
        console.log(req.cookies.currentUsername);
        console.log(req.cookies.currentUserId);
        console.log(req.cookies.accesstoken);
        //res.redirect("/");
    });

解决方法

Column       |            Type             |            Modifiers            
--------------------+-----------------------------+---------------------------------
 id                 | uuid                        | not null
 name               | character varying(255)      | 
 products           | character varying           | default '{}'::character varying

如何将products列更改为“character varying []”,并将相应的修饰符更改为默认的“{}”:: character varying []？本质上,我想将字符串转换为字符串数组.请注意,products列对字符数没有限制.

alter table "containers" alter "products" type character varying[];

抛出以下错误

ERROR: column “products” cannot be cast to type character varying[]

The USING option of SET DATA TYPE can actually specify any expression involving the old values of the row; that is,it can refer to other columns as well as the one being converted. This allows very general conversions to be done with the SET DATA TYPE Syntax. Because of this flexibility,the USING expression is not applied to the column’s default value (if any); the result might not be a constant expression as required for a default. This means that when there is no implicit or assignment cast from old to new type,SET DATA TYPE might fail to convert the default even though a USING clause is supplied. In such cases,drop the default with DROP DEFAULT,perform the ALTER TYPE,and then use SET DEFAULT to add a suitable new default.

alter table containers alter products drop default;
alter table containers alter products type text[] using array[products];
alter table containers alter products set default '{}';

这三个操作可以在一个语句中完成：

alter table containers 
    alter products drop default,alter products type text[] using array[products],alter products set default '{}';

我在SQL数据库中有一个字符串，表示一个URL。有些网址很短，有些很长。我真的不知道这是我可能遇到的最长的URL，所以为了安全起见，我会采用较大的值，例如256或512。

当我定义最大字符串长度时（例如，使用SQLAlchemy）：

url_field = Column(String(256))

即使实际的字符串较短，这是否也会占用每一行的空间（存储空间）？

我假设这与实现细节有关。我正在使用postgreSQL，但对sqlite和mysql也很感兴趣。