使用GORM在MySQL中获取NULL日期时间值

Question

I want to fetch the last visit_details row having out_time as NULL using Gorm. NIL is itself a type where VisitDetail OutTime is mysql.NullTime.

Code:-

var visitDetail models.VisitDetail
db.Where("out_time=? ", nil).Last(&visitDetail)

//model VisitDetails
type VisitDetail struct {
    Id              int
    Visitor         Visitor  `gorm:"foreignkey:ClientId;association_foreignkey:Id"`
    VisitorId       int      `gorm:"not null;"`
    Location        Location `gorm:"foreignkey:LocationId;association_foreignkey:Id"`
    LocationId      int      `gorm:"not null;"`
    Purpose         string
    InTime          time.Time `gorm:"not null;"`
    OutTime         mysql.NullTime
    User            User `gorm:"foreignkey:ClientId;association_foreignkey:Id"`
    UserId          int  `gorm:"not null;"`
    Status          int  `gorm:"not null;"`
    ApproveByClient int  `gorm:"not null;"`
}

Query:-

select * from visit_details where out_time is NULL order by id desc limit 1;
+----+------------+-------------+---------+---------------------+----------+---------+--------+-------------------+
| id | visitor_id | location_id | purpose | in_time             | out_time | user_id | status | approve_by_client |
+----+------------+-------------+---------+---------------------+----------+---------+--------+-------------------+
| 20 |          1 |           8 |         | 2018-02-20 17:13:25 | NULL     |    1609 |      0 |                 0 |
+----+------------+-------------+---------+---------------------+----------+---------+--------+-------------------+
1 row in set (0.04 sec)

Answer 1

Go doesn't recognize NULL in particular. I think you can achieve it using a raw query in GORM. like this.

db.Raw("SELECT * FROM visit_details WHERE out_time is NULL order by id desc limit 1").Scan(&visitDetail)

This is one one to fetch the column. Hope this helps.