Custom preloading sql cannot be used properly.

[sejeongdev]

Hello.

I was using the preload function using the subquery through custom preloading sql in gorm, but the recent update made it impossible to use the subquery in the preload.

go-gorm/playground#807
I've written a detailed case in the pull request above.

Preload("Pets", func(db *gorm.DB) *gorm.DB { subscope := db.Select("MAX(id) as id").Model(&Pet{}).Group("name") return db.Where("id in (?)", subscope)

I'd appreciate it if you could check it out.