https://www.cnblogs.com/kissdodog/p/3297894.html——这个讲清楚了。
https://blog.csdn.net/qq_15058425/article/details/78506193
https://blog.csdn.net/qq_43998763/article/details/103528559
https://cloud.tencent.com/developer/article/1695472
https://www.cnblogs.com/baiyuhong/p/9753173.html
https://blog.csdn.net/wushuo001/article/details/79600463
对于树状结构的数据库表,如何在一个表中查询多次,开始走了不少弯路,比如想尝试用子查询,方向不对。其实就是join查询使用数据库表别名(改变数据表名称)即可。
//价值表带mark分值
type UserMeritTopic2 struct {
// gorm.Model
Id int64 `json:"id"`
Title string `json:"title"`
Title1 string `json:"title1"` //价值分类名称
Title2 string `json:"title2"` //价值分类名称
Title3 string `json:"title3"` //价值分类名称
TopicTitle string `json:"topictitle"` //价值内容名称
Mark int `json:"mark"`
Content string `json:"content"`
User User
}
//测试查询,希望查询出树状结构表的父子孙
//最后用join查询重命名来解决了。
func GetMeritTopic2(mid, uid int64, state int) (usermerittopics []*UserMeritTopic2, err error) {
db := GetDB()
err = db.Table("admin_merit").Select("t2.title as title2,t1.title as title1,admin_merit.title as title,admin_merit_mark.mark as mark,merit_topic.title as topic_title,merit_topic.content as content").
Where("admin_merit.parent_id=?", mid).
Joins("INNER JOIN admin_merit AS t1 ON t1.id = admin_merit.parent_id").
Joins("INNER JOIN admin_merit AS t2 ON t2.id = t1.parent_id").
Joins("left JOIN merit_topic on merit_topic.merit_id=admin_merit.id").
Where("merit_topic.user_id = ? AND merit_topic.state=?", uid, state).
Joins("left JOIN admin_merit_mark on admin_merit_mark.merit_id = merit_topic.merit_id").
Scan(&usermerittopics).Error
return usermerittopics, err
}
gorm的查询结果如下:
[
{
"id": 0,
"title": "大型",
"title1": "专业负责人",
"title2": "项目管理类",
"title3": "",
"topictitle": "阿斯顿发生发送的",
"mark": 4,
"content": "阿斯蒂芬",
}
]