// 使用指针 type User struct { ID int64 Name *string`gorm:"default:'小王子'"` Age int64 } user := User{Name: new(string), Age: 18))} db.Create(&user) // 此时数据库中该条记录name字段的值就是''
使用Scanner/Valuer接口方式实现零值存入数据库
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// 使用 Scanner/Valuer type User struct { ID int64 Name sql.NullString `gorm:"default:'小王子'"`// sql.NullString 实现了Scanner/Valuer接口 Age int64 } user := User{Name: sql.NullString{"", true}, Age:18} db.Create(&user) // 此时数据库中该条记录name字段的值就是''
扩展创建选项
例如PostgreSQL数据库中可以使用下面的方式实现合并插入, 有则更新, 无则插入。
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// 为Instert语句添加扩展SQL选项 db.Set("gorm:insert_option", "ON CONFLICT").Create(&product) // INSERT INTO products (name, code) VALUES ("name", "code") ON CONFLICT;
查询
一般查询
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// 根据主键查询第一条记录 db.First(&user) //// SELECT * FROM users ORDER BY id LIMIT 1;
// 随机获取一条记录 db.Take(&user) //// SELECT * FROM users LIMIT 1;
// 根据主键查询最后一条记录 db.Last(&user) //// SELECT * FROM users ORDER BY id DESC LIMIT 1;
// 查询所有的记录 db.Find(&users) //// SELECT * FROM users;
// 查询指定的某条记录(仅当主键为整型时可用) db.First(&user, 10) //// SELECT * FROM users WHERE id = 10;
// Get first matched record db.Where("name = ?", "jinzhu").First(&user) //// SELECT * FROM users WHERE name = 'jinzhu' limit 1;
// Get all matched records db.Where("name = ?", "jinzhu").Find(&users) //// SELECT * FROM users WHERE name = 'jinzhu';
// <> db.Where("name <> ?", "jinzhu").Find(&users) //// SELECT * FROM users WHERE name <> 'jinzhu';
// IN db.Where("name IN (?)", []string{"jinzhu", "jinzhu 2"}).Find(&users) //// SELECT * FROM users WHERE name in ('jinzhu','jinzhu 2');
// LIKE db.Where("name LIKE ?", "%jin%").Find(&users) //// SELECT * FROM users WHERE name LIKE '%jin%';
// AND db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users) //// SELECT * FROM users WHERE name = 'jinzhu' AND age >= 22;
// Time db.Where("updated_at > ?", lastWeek).Find(&users) //// SELECT * FROM users WHERE updated_at > '2000-01-01 00:00:00';
// BETWEEN db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users) //// SELECT * FROM users WHERE created_at BETWEEN '2000-01-01 00:00:00' AND '2000-01-08 00:00:00';
Struct & Map查询
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// 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);
db.Not("name", "jinzhu").First(&user) //// SELECT * FROM users WHERE name <> "jinzhu" LIMIT 1;
// Not In db.Not("name", []string{"jinzhu", "jinzhu 2"}).Find(&users) //// SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");
// Not In slice of primary keys db.Not([]int64{1,2,3}).First(&user) //// SELECT * FROM users WHERE id NOT IN (1,2,3);
db.Not([]int64{}).First(&user) //// SELECT * FROM users;
// Plain SQL db.Not("name = ?", "jinzhu").First(&user) //// SELECT * FROM users WHERE NOT(name = "jinzhu");
// Struct db.Not(User{Name: "jinzhu"}).First(&user) //// SELECT * FROM users WHERE name <> "jinzhu";
Or条件
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db.Where("role = ?", "admin").Or("role = ?", "super_admin").Find(&users) //// SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';
// Struct db.Where("name = 'jinzhu'").Or(User{Name: "jinzhu 2"}).Find(&users) //// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';
// Map db.Where("name = 'jinzhu'").Or(map[string]interface{}{"name": "jinzhu 2"}).Find(&users) //// SELECT * FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2';
// 未找到 db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrInit(&user) //// SELECT * FROM USERS WHERE name = 'non_existing'; //// user -> User{Name: "non_existing", Age: 20}
db.Where(User{Name: "non_existing"}).Attrs("age", 20).FirstOrInit(&user) //// SELECT * FROM USERS WHERE name = 'non_existing'; //// user -> User{Name: "non_existing", Age: 20}
// 找到 db.Where(User{Name: "Jinzhu"}).Attrs(User{Age: 30}).FirstOrInit(&user) //// SELECT * FROM USERS WHERE name = jinzhu'; //// user -> User{Id: 111, Name: "Jinzhu", Age: 20}
// 未找到 db.Where(User{Name: "non_existing"}).Attrs(User{Age: 20}).FirstOrCreate(&user) //// SELECT * FROM users WHERE name = 'non_existing'; //// INSERT INTO "users" (name, age) VALUES ("non_existing", 20); //// user -> User{Id: 112, Name: "non_existing", Age: 20}
// 找到 db.Where(User{Name: "jinzhu"}).Attrs(User{Age: 30}).FirstOrCreate(&user) //// SELECT * FROM users WHERE name = 'jinzhu'; //// user -> User{Id: 111, Name: "jinzhu", Age: 20}
Assign
不管记录是否找到，都将参数赋值给 struct 并保存至数据库.
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// 未找到 db.Where(User{Name: "non_existing"}).Assign(User{Age: 20}).FirstOrCreate(&user) //// SELECT * FROM users WHERE name = 'non_existing'; //// INSERT INTO "users" (name, age) VALUES ("non_existing", 20); //// user -> User{Id: 112, Name: "non_existing", Age: 20}
// 找到 db.Where(User{Name: "jinzhu"}).Assign(User{Age: 30}).FirstOrCreate(&user) //// SELECT * FROM users WHERE name = 'jinzhu'; //// UPDATE users SET age=30 WHERE id = 111; //// user -> User{Id: 111, Name: "jinzhu", Age: 30}
高级查询
子查询
基于 *gorm.expr 的子查询
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db.Where("amount > ?", db.Table("orders").Select("AVG(amount)").Where("state = ?", "paid").SubQuery()).Find(&orders) // SELECT * FROM "orders" WHERE "orders"."deleted_at" IS NULL AND (amount > (SELECT AVG(amount) FROM "orders" WHERE (state = 'paid')));
选择字段
Select，指定你想从数据库中检索出的字段，默认会选择全部字段。
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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;
db.Order("age desc, name").Find(&users) //// SELECT * FROM users ORDER BY age desc, name;
// 多字段排序 db.Order("age desc").Order("name").Find(&users) //// SELECT * FROM users ORDER BY age desc, name;
// 覆盖排序 db.Order("age desc").Find(&users1).Order("age", true).Find(&users2) //// SELECT * FROM users ORDER BY age desc; (users1) //// SELECT * FROM users ORDER BY age; (users2)
数量
Limit，指定从数据库检索出的最大记录数。
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db.Limit(3).Find(&users) //// SELECT * FROM users LIMIT 3;
// -1 取消 Limit 条件 db.Limit(10).Find(&users1).Limit(-1).Find(&users2) //// SELECT * FROM users LIMIT 10; (users1) //// SELECT * FROM users; (users2)
偏移
Offset，指定开始返回记录前要跳过的记录数。
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db.Offset(3).Find(&users) //// SELECT * FROM users OFFSET 3;
// -1 取消 Offset 条件 db.Offset(10).Find(&users1).Offset(-1).Find(&users2) //// SELECT * FROM users OFFSET 10; (users1) //// SELECT * FROM users; (users2)
总数
Count，该 model 能获取的记录总数。
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db.Where("name = ?", "jinzhu").Or("name = ?", "jinzhu 2").Find(&users).Count(&count) //// SELECT * from USERS WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (users) //// SELECT count(*) FROM users WHERE name = 'jinzhu' OR name = 'jinzhu 2'; (count)
db.Model(&User{}).Where("name = ?", "jinzhu").Count(&count) //// SELECT count(*) FROM users WHERE name = 'jinzhu'; (count)
db.Table("deleted_users").Count(&count) //// SELECT count(*) FROM deleted_users;
db.Table("deleted_users").Select("count(distinct(name))").Count(&count) //// SELECT count( distinct(name) ) FROM deleted_users; (count)
rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Rows() for rows.Next() { ... }
// 使用Scan将多条结果扫描进事先准备好的结构体切片中 type Result struct { Date time.Time Total int } var rets []Result db.Table("users").Select("date(created_at) as date, sum(age) as total").Group("date(created_at)").Scan(&rets)
rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Rows() for rows.Next() { ... }
type Result struct { Date time.Time Total int64 } db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Scan(&results)
连接
Joins，指定连接条件
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rows, err := db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Rows() for rows.Next() { ... }
db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&results)
// 多连接及参数 db.Joins("JOIN emails ON emails.user_id = users.id AND emails.email = ?", "jinzhu@example.org").Joins("JOIN credit_cards ON credit_cards.user_id = users.id").Where("credit_cards.number = ?", "411111111111").Find(&user)
// 更新单个属性，类似于 `Update` db.Model(&user).UpdateColumn("name", "hello") //// UPDATE users SET name='hello' WHERE id = 111;
// 更新多个属性，类似于 `Updates` db.Model(&user).UpdateColumns(User{Name: "hello", Age: 18}) //// UPDATE users SET name='hello', age=18 WHERE id = 111;
批量更新
批量更新时Hooks（钩子函数）不会运行。
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db.Table("users").Where("id IN (?)", []int{10, 11}).Updates(map[string]interface{}{"name": "hello", "age": 18}) //// UPDATE users SET name='hello', age=18 WHERE id IN (10, 11);