Question

I m与复杂的结构数据库合作,在更新后,我们开始使用全球资源评估,因此,我需要利用全球资源评估来改变这一说法。

query := `
  SELECT * FROM foo
  UNION ALL
  SELECT * FROM bar WHERE id=1`
rows, err := db.Query(query)

这样做的最佳方式是什么?

Answer 1

注:gorm 直接使用db.Raw。

db.Raw("? UNION ?",
    db.Select("*").Model(&Foo{}),
    db.Select("*").Model(&Bar{}),
).Scan(&union)

the above will produce something like the following:

SELECT * FROM "foos"
WHERE "foos"."deleted_at" IS NULL
UNION
SELECT * FROM "bars"
WHERE "bars"."deleted_at" IS NULL

Answer 2

From this github issue, there s a workaround where if you don t want to use db.Raw, you can actually use Joins. Something like the following should work.

db.Table("foo").Joins("UNION ?", db.Table("bar").Where("id = ?", 1)).Scan(&results)

并非偶然,但是,由于你,你可以使用其他链式方法:Raw。

Answer 3

thanks to @mkopriva, db.Raw will do the job. although the code provided might not work with legacy gorm(github.com/jinzhu/gorm), you need to convert *gorm.DB to gorm.SqlExpr in raw clause

db.Raw("? UNION ?",
    db.Select("*").Model(&Foo{}).QueryExpr(),
    db.Select("*").Model(&Bar{}).QueryExpr(),
).Scan(&union)

友情链接