Diligence neglected in play --- Go of GORM query

Inquire

//通过主键查询第一条记录
db.First(&user)
//// SELECT * FROM users ORDER BY id LIMIT 1;

// 随机取一条记录
db.Take(&user)
//// SELECT * FROM users LIMIT 1;

// 通过主键查询最后一条记录
db.Last(&user)
//// SELECT * FROM users ORDER BY id DESC LIMIT 1;

// 拿到所有的记录
db.Find(&users)
//// SELECT * FROM users;

// 查询指定的某条记录(只可在主键为整数型时使用)
db.First(&user, 10)
//// SELECT * FROM users WHERE id = 10;

Where conditions

Ordinary SQL

// 获取第一条匹配的记录
db.Where("name = ?", "jinzhu").First(&user)
//// SELECT * FROM users WHERE name = 'jinzhu' limit 1;

// 获取全部匹配的记录
db.Where("name = ?", "jinzhu").Find(&users)
//// SELECT * FROM users WHERE name = 'jinzhu';

// <>
db.Where("name <> ?", "jinzhu").Find(&users)

// IN
db.Where("name IN (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users)

// LIKE
db.Where("name LIKE ?", "%jin%").Find(&users)

// AND
db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)

// 时间
db.Where("updated_at > ?", lastWeek).Find(&users)

// BETWEEN
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)

Struct & Map

// Struct
db.Where(&User{Name: "jinzhu", Age: 20}).First(&user)
//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20 LIMIT 1;

// Map
db.Where(map[string]interface{}{"name": "jinzhu", "age": 20}).Find(&users)
//// SELECT * FROM users WHERE name = "jinzhu" AND age = 20;

// 主键的切片
db.Where([]int64{20, 21, 22}).Find(&users)
//// SELECT * FROM users WHERE id IN (20, 21, 22);

When prompted by query structure, will GORM query by only non-zero field, this means that if you field is 0, '', when other values ​​false or zero, will not be used to construct a query ,E.g:

db.Where(&User{Name: "jinzhu", Age: 0}).Find(&users)
//// SELECT * FROM users WHERE name = "jinzhu";

You can use a pointer or implement Scanner / Valuer interfaces to avoid this problem.

// 使用指针
type User struct {
  gorm.Model
  Name string
  Age  *int
}

// 使用 Scanner/Valuer
type User struct {
  gorm.Model
  Name string
  Age  sql.NullInt64  // sql.NullInt64 实现了 Scanner/Valuer 接口
}

Select Fields

Select, specify the fields you want to retrieve from the database, the default will select all of the fields.

db.Select("name, age").Find(&users)
//// SELECT name, age FROM users;

db.Select([]string{"name", "age"}).Find(&users)
//// SELECT name, age FROM users;

db.Table("users").Select("COALESCE(age,?)", 42).Rows()
//// SELECT COALESCE(age,'42') FROM users;