CRUD Interface - Query - 《GORM v1.23.5 Documentation》

Retrieving a single object
- Retrieving objects with primary key
Retrieving all objects
Conditions
Selecting Specific Fields
Order
Limit & Offset
Group By & Having
Distinct
Joins
- Joins Preloading
- Joins a Derived Table
Scan

Retrieving a single object

GORM provides First, Take, Last methods to retrieve a single object from the database, it adds LIMIT 1 condition when querying the database, and it will return the error ErrRecordNotFound if no record is found.

1. // Get the first record ordered by primary key
2. db.First(&user)
3. // SELECT * FROM users ORDER BY id LIMIT 1;

5. // Get one record, no specified order
6. db.Take(&user)
7. // SELECT * FROM users LIMIT 1;

9. // Get last record, ordered by primary key desc
10. db.Last(&user)
11. // SELECT * FROM users ORDER BY id DESC LIMIT 1;

13. result := db.First(&user)
14. result.RowsAffected // returns count of records found
15. result.Error        // returns error or nil

17. // check error ErrRecordNotFound
18. errors.Is(result.Error, gorm.ErrRecordNotFound)

If you want to avoid the ErrRecordNotFound error, you could use Find like db.Limit(1).Find(&user), the Find method accepts both struct and slice data

The First and Last methods will find the first and last record (respectively) as ordered by primary key. They only work when a pointer to the destination struct is passed to the methods as argument or when the model is specified using db.Model(). Additionally, if no primary key is defined for relevant model, then the model will be ordered by the first field. For example:

1. var user User
2. var users []User

4. // works because destination struct is passed in
5. db.First(&user)
6. // SELECT * FROM `users` ORDER BY `users`.`id` LIMIT 1

8. // works because model is specified using `db.Model()`
9. result := map[string]interface{}{}
10. db.Model(&User{}).First(&result)
11. // SELECT * FROM `users` ORDER BY `users`.`id` LIMIT 1

13. // doesn't work
14. result := map[string]interface{}{}
15. db.Table("users").First(&result)

17. // works with Take
18. result := map[string]interface{}{}
19. db.Table("users").Take(&result)

21. // no primary key defined, results will be ordered by first field (i.e., `Code`)
22. type Language struct {
23. Code string
24. Name string
25. }
26. db.First(&Language{})
27. // SELECT * FROM `languages` ORDER BY `languages`.`code` LIMIT 1

Retrieving objects with primary key

Objects can be retrieved using primary key by using Inline Conditions if the primary key is a number. When working with strings, extra care needs to be taken to avoid SQL Injection; check out Security section for details.

1. db.First(&user, 10)
2. // SELECT * FROM users WHERE id = 10;

4. db.First(&user, "10")
5. // SELECT * FROM users WHERE id = 10;

7. db.Find(&users, []int{1,2,3})
8. // SELECT * FROM users WHERE id IN (1,2,3);

If the primary key is a string (for example, like a uuid), the query will be written as follows:

1. db.First(&user, "id = ?", "1b74413f-f3b8-409f-ac47-e8c062e3472a")
2. // SELECT * FROM users WHERE id = "1b74413f-f3b8-409f-ac47-e8c062e3472a";

When the destination object has a primary value, the primary key will be used to build the condition, for example:

1. var user = User{ID: 10}
2. db.First(&user)
3. // SELECT * FROM users WHERE id = 10;

5. var result User
6. db.Model(User{ID: 10}).First(&result)
7. // SELECT * FROM users WHERE id = 10;

Retrieving all objects

1. // Get all records
2. result := db.Find(&users)
3. // SELECT * FROM users;

5. result.RowsAffected // returns found records count, equals `len(users)`
6. result.Error        // returns error

Conditions

String Conditions

1. // Get first matched record
2. db.Where("name = ?", "jinzhu").First(&user)
3. // SELECT * FROM users WHERE name = 'jinzhu' ORDER BY id LIMIT 1;

5. // Get all matched records
6. db.Where("name <> ?", "jinzhu").Find(&users)
7. // SELECT * FROM users WHERE name <> 'jinzhu';

9. // IN
10. db.Where("name IN ?", []string{"jinzhu", "jinzhu 2"}).Find(&users)
11. // SELECT * FROM users WHERE name IN ('jinzhu','jinzhu 2');

13. // LIKE
14. db.Where("name LIKE ?", "%jin%").Find(&users)
15. // SELECT * FROM users WHERE name LIKE '%jin%';

17. // AND
18. db.Where("name = ? AND age >= ?", "jinzhu", "22").Find(&users)
19. // SELECT * FROM users WHERE name = 'jinzhu' AND age >= 22;

21. // Time
22. db.Where("updated_at > ?", lastWeek).Find(&users)
23. // SELECT * FROM users WHERE updated_at > '2000-01-01 00:00:00';

25. // BETWEEN
26. db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)
27. // SELECT * FROM users WHERE created_at BETWEEN '2000-01-01 00:00:00' AND '2000-01-08 00:00:00';

Struct & Map Conditions

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

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

9. // Slice of primary keys
10. db.Where([]int64{20, 21, 22}).Find(&users)
11. // SELECT * FROM users WHERE id IN (20, 21, 22);

NOTE When querying with struct, GORM will only query with non-zero fields, that means if your field’s value is 0, '', false or other zero values, it won’t be used to build query conditions, for example:

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

To include zero values in the query conditions, you can use a map, which will include all key-values as query conditions, for example:

1. db.Where(map[string]interface{}{"Name": "jinzhu", "Age": 0}).Find(&users)
2. // SELECT * FROM users WHERE name = "jinzhu" AND age = 0;

For more details, see Specify Struct search fields.

Specify Struct search fields

When searching with struct, you can specify which particular values from the struct to use in the query conditions by passing in the relevant field name or the dbname to Where(), for example:

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

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

Inline Condition

Query conditions can be inlined into methods like First and Find in a similar way to Where.

1. // Get by primary key if it were a non-integer type
2. db.First(&user, "id = ?", "string_primary_key")
3. // SELECT * FROM users WHERE id = 'string_primary_key';

5. // Plain SQL
6. db.Find(&user, "name = ?", "jinzhu")
7. // SELECT * FROM users WHERE name = "jinzhu";

9. db.Find(&users, "name <> ? AND age > ?", "jinzhu", 20)
10. // SELECT * FROM users WHERE name <> "jinzhu" AND age > 20;

12. // Struct
13. db.Find(&users, User{Age: 20})
14. // SELECT * FROM users WHERE age = 20;

16. // Map
17. db.Find(&users, map[string]interface{}{"age": 20})
18. // SELECT * FROM users WHERE age = 20;

Not Conditions

Build NOT conditions, works similar to Where

1. db.Not("name = ?", "jinzhu").First(&user)
2. // SELECT * FROM users WHERE NOT name = "jinzhu" ORDER BY id LIMIT 1;

4. // Not In
5. db.Not(map[string]interface{}{"name": []string{"jinzhu", "jinzhu 2"}}).Find(&users)
6. // SELECT * FROM users WHERE name NOT IN ("jinzhu", "jinzhu 2");

8. // Struct
9. db.Not(User{Name: "jinzhu", Age: 18}).First(&user)
10. // SELECT * FROM users WHERE name <> "jinzhu" AND age <> 18 ORDER BY id LIMIT 1;

12. // Not In slice of primary keys
13. db.Not([]int64{1,2,3}).First(&user)
14. // SELECT * FROM users WHERE id NOT IN (1,2,3) ORDER BY id LIMIT 1;

Or Conditions

1. db.Where("role = ?", "admin").Or("role = ?", "super_admin").Find(&users)
2. // SELECT * FROM users WHERE role = 'admin' OR role = 'super_admin';

4. // Struct
5. db.Where("name = 'jinzhu'").Or(User{Name: "jinzhu 2", Age: 18}).Find(&users)
6. // SELECT * FROM users WHERE name = 'jinzhu' OR (name = 'jinzhu 2' AND age = 18);

8. // Map
9. db.Where("name = 'jinzhu'").Or(map[string]interface{}{"name": "jinzhu 2", "age": 18}).Find(&users)
10. // SELECT * FROM users WHERE name = 'jinzhu' OR (name = 'jinzhu 2' AND age = 18);

For more complicated SQL queries. please also refer to Group Conditions in Advanced Query.

Selecting Specific Fields

Select allows you to specify the fields that you want to retrieve from database. Otherwise, GORM will select all fields by default.

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

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

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

Also check out Smart Select Fields

Order

Specify order when retrieving records from the database

1. db.Order("age desc, name").Find(&users)
2. // SELECT * FROM users ORDER BY age desc, name;

4. // Multiple orders
5. db.Order("age desc").Order("name").Find(&users)
6. // SELECT * FROM users ORDER BY age desc, name;

8. db.Clauses(clause.OrderBy{
9. Expression: clause.Expr{SQL: "FIELD(id,?)", Vars: []interface{}{[]int{1, 2, 3}}, WithoutParentheses: true},
10. }).Find(&User{})
11. // SELECT * FROM users ORDER BY FIELD(id,1,2,3)

Limit & Offset

Limit specify the max number of records to retrieve Offset specify the number of records to skip before starting to return the records

1. db.Limit(3).Find(&users)
2. // SELECT * FROM users LIMIT 3;

4. // Cancel limit condition with -1
5. db.Limit(10).Find(&users1).Limit(-1).Find(&users2)
6. // SELECT * FROM users LIMIT 10; (users1)
7. // SELECT * FROM users; (users2)

9. db.Offset(3).Find(&users)
10. // SELECT * FROM users OFFSET 3;

12. db.Limit(10).Offset(5).Find(&users)
13. // SELECT * FROM users OFFSET 5 LIMIT 10;

15. // Cancel offset condition with -1
16. db.Offset(10).Find(&users1).Offset(-1).Find(&users2)
17. // SELECT * FROM users OFFSET 10; (users1)
18. // SELECT * FROM users; (users2)

Refer to Pagination for details on how to make a paginator

Group By & Having

1. type result struct {
2. Date  time.Time
3. Total int
4. }

6. db.Model(&User{}).Select("name, sum(age) as total").Where("name LIKE ?", "group%").Group("name").First(&result)
7. // SELECT name, sum(age) as total FROM `users` WHERE name LIKE "group%" GROUP BY `name` LIMIT 1

10. db.Model(&User{}).Select("name, sum(age) as total").Group("name").Having("name = ?", "group").Find(&result)
11. // SELECT name, sum(age) as total FROM `users` GROUP BY `name` HAVING name = "group"

13. rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Rows()
14. defer rows.Close()
15. for rows.Next() {
16. ...
17. }

19. rows, err := db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Rows()
20. defer rows.Close()
21. for rows.Next() {
22. ...
23. }

25. type Result struct {
26. Date  time.Time
27. Total int64
28. }
29. db.Table("orders").Select("date(created_at) as date, sum(amount) as total").Group("date(created_at)").Having("sum(amount) > ?", 100).Scan(&results)

Distinct

Selecting distinct values from the model

1. db.Distinct("name", "age").Order("name, age desc").Find(&results)

Distinct works with Pluck and Count too

Joins

Specify Joins conditions

1. type result struct {
2. Name  string
3. Email string
4. }

6. db.Model(&User{}).Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&result{})
7. // SELECT users.name, emails.email FROM `users` left join emails on emails.user_id = users.id

9. rows, err := db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Rows()
10. for rows.Next() {
11. ...
12. }

14. db.Table("users").Select("users.name, emails.email").Joins("left join emails on emails.user_id = users.id").Scan(&results)

16. // multiple joins with parameter
17. 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)

Joins Preloading

You can use Joins eager loading associations with a single SQL, for example:

1. db.Joins("Company").Find(&users)
2. // SELECT `users`.`id`,`users`.`name`,`users`.`age`,`Company`.`id` AS `Company__id`,`Company`.`name` AS `Company__name` FROM `users` LEFT JOIN `companies` AS `Company` ON `users`.`company_id` = `Company`.`id`;

Join with conditions

1. db.Joins("Company", DB.Where(&Company{Alive: true})).Find(&users)
2. // SELECT `users`.`id`,`users`.`name`,`users`.`age`,`Company`.`id` AS `Company__id`,`Company`.`name` AS `Company__name` FROM `users` LEFT JOIN `companies` AS `Company` ON `users`.`company_id` = `Company`.`id` AND `Company`.`alive` = true;

For more details, please refer to Preloading (Eager Loading).

Joins a Derived Table

You can also use Joins to join a derived table.

1. type User struct {
2. Id  int
3. Age int
4. }

6. type Order struct {
7. UserId     int
8. FinishedAt *time.Time
9. }

11. query := db.Table("order").Select("MAX(order.finished_at) as latest").Joins("left join user user on order.user_id = user.id").Where("user.age > ?", 18).Group("order.user_id")
12. db.Model(&Order{}).Joins("join (?) q on order.finished_at = q.latest", query).Scan(&results)
13. // SELECT `order`.`user_id`,`order`.`finished_at` FROM `order` join (SELECT MAX(order.finished_at) as latest FROM `order` left join user user on order.user_id = user.id WHERE user.age > 18 GROUP BY `order`.`user_id`) q on order.finished_at = q.latest

Scan

Scanning results into a struct works similarly to the way we use Find

1. type Result struct {
2. Name string
3. Age  int
4. }

6. var result Result
7. db.Table("users").Select("name", "age").Where("name = ?", "Antonio").Scan(&result)

9. // Raw SQL
10. db.Raw("SELECT name, age FROM users WHERE name = ?", "Antonio").Scan(&result)