英文:
golang - mysql driver - database functions
问题
我已经创建了一个结构体来存储空间类型，并且创建了一个扫描函数来帮助查询数据库中的行。我在插入这种类型时遇到了问题。
我可以使用以下 SQL 语句插入数据：
INSERT INTO 'table' ('spot') VALUES (GeomFromText('POINT(10 10)'));
如果我在 database/sql/driver 中使用 Value 接口；
> type Value interface{}
>
> Value 是驱动程序必须能够处理的值。它可以是 nil，也可以是以下类型之一的实例：
>
> int64
>
> float64
>
> bool
>
> []byte
>
> string [*] 除了 Rows.Next 之外的所有地方。
>
> time.Time
并使用以下代码；
func (p Point) Value() (driver.Value, error) {
return "GeomFromText('" + p.ToWKT() + "')", nil
}
我最终得到的 SQL 语句发送到数据库如下；
INSERT INTO 'table' ('spot') VALUES ('GeomFromText('POINT(10 10)')');
问题在于函数 GeomFromText 被引号包围。有没有办法避免这种情况？我正在使用 gorm，并尽量减少原始 SQL 查询的使用。
数据库端使用的是 point 类型。
英文:
I have created a struct to store spatial types and I have created a scan function to help query rows in my database. I am having issues inserting this type.
I can insert data using the following sql;
INSERT INTO 'table' ('spot') VALUES (GeomFromText('POINT(10 10)'));
If I use Value interface in database/sql/driver;
> type Value interface{}
>
> Value is a value that drivers must be able to handle. It is either nil or an instance of one of these types:
>
> int64
>
> float64
>
> bool
>
> []byte
>
> string [*] everywhere except from Rows.Next.
>
> time.Time
And use this code;
func (p Point) Value() (driver.Value, error) {
return "GeomFromText('" + p.ToWKT() + "')", nil
}
I end up with the following sql statement going to the database;
INSERT INTO 'table' ('spot') VALUES ('GeomFromText('POINT(10 10)')');
The issue being that the function GeomFromText is in quotes. Is there a way to avoid this scenario? I am using gorm and trying to keep raw sql queries to a minimum.
The mysql type being used on the database end is a point.
答案1
得分: 1
请查看下面两个链接，其中的概念是从这里借用的：
Schema
创建表Points：
create table Points
(
id int auto_increment primary key,
name VARCHAR(20) not null,
location Point NOT NULL,
description VARCHAR(200) not null,
SPATIAL INDEX(location),
key(name)
)engine=MyISAM; -- 用于使用空间索引和避免错误1464
-- 插入一行数据，以便后面证明Update语句可以工作
INSERT INTO Points (name, location, description) VALUES
('point1', GeomFromText('POINT(31.5 42.2)'), 'some place');
Update语句
这个概念是从这里借用的：http://stackoverflow.com/a/7135890
UPDATE Points
set location = PointFromText(CONCAT('POINT(',13.33,' ',26.48,')'))
where id=1;
验证
select * from points;
（当你打开Value Editor查看blob时，点的位置已经更新）
所以，要点是在更新语句中使用concat()函数。
英文:
Please see the two urls below where the concept was poached from
Schema
-- http://howto-use-mysql-spatial-ext.blogspot.com/
create table Points
( id int auto_increment primary key,
name VARCHAR(20) not null,
location Point NOT NULL,
description VARCHAR(200) not null,
SPATIAL INDEX(location),
key(name)
)engine=MyISAM; -- for use of spatial indexes and avoiding error 1464
-- insert a row, so we can prove Update later will work
INSERT INTO Points (name, location, description) VALUES
( 'point1' , GeomFromText( ' POINT(31.5 42.2) ' ) , 'some place');
Update statement
-- concept borrowed from http://stackoverflow.com/a/7135890
UPDATE Points
set location = PointFromText(CONCAT('POINT(',13.33,' ',26.48,')'))
where id=1;
Verify
select * from points;
(when you open the Value Editor to see the blob, the point is updated)
So, the takeaway is to play with the concat() inside of the update statement.
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