英文:
Is this a valid SQL query
问题
以下是要翻译的内容：
// 第一种方式
db.Table("tbl1 AS A").Select("A.field1").Joins("JOIN tbl2 AS B ON A.field2 = B.field2").Find(&result)
// 第二种方式
db.Table("tbl1 AS A").Select("field1").Joins("JOIN tbl2 AS B ON A.field2 = B.field2").Find(&result)
假设这是有效的，你会如何使用 Golang 和 GORM 进行转换？
英文:
SELECT A.field1 FROM tbl1 AS A,tbl2 AS B WHERE A.field2=B.field2;
Or this the correct way
SELECT field1 FROM tbl1 AS A,tbl2 AS B WHERE A.field2=B.field2;
Assuming this is valid, how would you convert it into golang using gorm?
答案1
得分: 4
实际上这取决于情况。如果field1只存在于tbl1或tbl2中，那么两种写法都可以。否则，第一种写法是正确的，可以消除歧义。
顺便说一句，与其使用这种旧式的内连接写法，你应该这样写：
SELECT A.field1
FROM tbl1 AS A
INNER JOIN tbl2 AS B ON A.field2=B.field2;
使用gorm的话，可以这样写：
db.Joins("Tbl2").Find(&tbl1)
如果你说你只了解这个SQL，可以使用原始的SQL语句来实现：
var field1 string
rows, err := db.Raw("SELECT A.field1 FROM tbl1 AS A INNER JOIN tbl2 AS B ON A.field2=B.field2 WHERE B.Field3 = ?", "something").Rows()
defer rows.Close()
for rows.Next() {
rows.Scan(&field1)
// ...
}
英文:
Actually it depends. If field1 only exists in tbl1 or tbl2 then both would work. Otherwise first one is correct and removes ambiguity.
BTW, instead of using such old style inner join you should write that as:
SELECT A.field1
FROM tbl1 AS A
inner join tbl2 AS B ON A.field2=B.field2;
With gorm:
db.Joins("Tbl2").Find(&tbl1)
EDIT? Since you are saying you don't know anything other than this SQL, you could use raw SQL as such:
var field1 string
rows, err := db.Raw("SELECT A.field1 FROM tbl1 AS A inner join tbl2 AS B on A.field2=B.field2 where b.Field3 = ?", "something").Rows()
defer rows.Close()
for rows.Next() {
rows.Scan(&field1)
// ...
}
答案2
得分: 0
type Tbl1 struct {
....
}
var Fields []struct {
Field1 string
}
-- gorm
err := gorm.Model(&Tbl1{}).
Joins("tbl2 ON tbl1.field2 = tbl2.field2").
Select("tbl1.field1").
Scan(&Fields).Error
if err!=nil {
...
}
参考：https://gorm.io/docs/query.html
英文:
type Tbl1 struct {
....
}
var Fields []struct {
Field1 string
}
-- gorm
err := gorm.Model(&Tbl1{}).
Joins("tbl2 ON tbl1.field2 = tbl2.field2").
Select("tbl1.field1").
Scan(&Fields).Error
if err!=nil {
...
}
Reference: https://gorm.io/docs/query.html
答案3
得分: 0
模型
type tbl1 struct {
field1 string
field2 string
}
type tbl2 struct {
field1 string
field2 string
}
SQL
SELECT A.field1 FROM tbl1 A INNER JOIN tbl2 B ON A.field2 = B.field2
Gorm
db.
Model(tbl1{}).
Select("A.field1").
Joins("INNER JOIN tbl2 B ON A.field2 = B.field2").
Scan(&tbl1{})
英文:
Models
type tbl1 struct {
field1 string
field2 string
}
type tbl2 struct {
field1 string
field2 string
}
SQL
SELECT A.field1 FROM tbl1 A INNER JOIN tbl2 B ON A.field2 = B.field2
Gorm
db.
Model(tbl1{}).
Select("A.field1").
Joins("INNER JOIN tbl2 B ON A.field2 = B.field2").
Scan(&tbl1{})
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论