gojsj2025/backend/docs/gorm/SQL Builder.md

SQL Builder Raw SQL Query Raw SQL with Scan

type Result struct { ID int Name string Age int }

var result Result db.Raw("SELECT id, name, age FROM users WHERE id = ?", 3).Scan(&result)

db.Raw("SELECT id, name, age FROM users WHERE name = ?", "jinzhu").Scan(&result)

var age int db.Raw("SELECT SUM(age) FROM users WHERE role = ?", "admin").Scan(&age)

var users []User db.Raw("UPDATE users SET name = ? WHERE age = ? RETURNING id, name", "jinzhu", 20).Scan(&users) Exec with Raw SQL

db.Exec("DROP TABLE users") db.Exec("UPDATE orders SET shipped_at = ? WHERE id IN ?", time.Now(), []int64{1, 2, 3})

// Exec with SQL Expression db.Exec("UPDATE users SET money = ? WHERE name = ?", gorm.Expr("money * ? + ?", 10000, 1), "jinzhu") NOTE GORM allows cache prepared statement to increase performance, checkout Performance for details

Named Argument GORM supports named arguments with sql.NamedArg, map[string]interface{}{} or struct, for example:

db.Where("name1 = @name OR name2 = @name", sql.Named("name", "jinzhu")).Find(&user) // SELECT * FROM users WHERE name1 = "jinzhu" OR name2 = "jinzhu"

db.Where("name1 = @name OR name2 = @name", map[string]interface{}{"name": "jinzhu2"}).First(&result3) // SELECT * FROM users WHERE name1 = "jinzhu2" OR name2 = "jinzhu2" ORDER BY users.id LIMIT 1

// Named Argument with Raw SQL db.Raw("SELECT _ FROM users WHERE name1 = @name OR name2 = @name2 OR name3 = @name", sql.Named("name", "jinzhu1"), sql.Named("name2", "jinzhu2")).Find(&user) // SELECT _ FROM users WHERE name1 = "jinzhu1" OR name2 = "jinzhu2" OR name3 = "jinzhu1"

db.Exec("UPDATE users SET name1 = @name, name2 = @name2, name3 = @name", sql.Named("name", "jinzhunew"), sql.Named("name2", "jinzhunew2")) // UPDATE users SET name1 = "jinzhunew", name2 = "jinzhunew2", name3 = "jinzhunew"

db.Raw("SELECT _ FROM users WHERE (name1 = @name AND name3 = @name) AND name2 = @name2", map[string]interface{}{"name": "jinzhu", "name2": "jinzhu2"}).Find(&user) // SELECT _ FROM users WHERE (name1 = "jinzhu" AND name3 = "jinzhu") AND name2 = "jinzhu2"

type NamedArgument struct { Name string Name2 string }

db.Raw("SELECT _ FROM users WHERE (name1 = @Name AND name3 = @Name) AND name2 = @Name2", NamedArgument{Name: "jinzhu", Name2: "jinzhu2"}).Find(&user) // SELECT _ FROM users WHERE (name1 = "jinzhu" AND name3 = "jinzhu") AND name2 = "jinzhu2" DryRun Mode Generate SQL and its arguments without executing, can be used to prepare or test generated SQL, Checkout Session for details

stmt := db.Session(&gorm.Session{DryRun: true}).First(&user, 1).Statement stmt.SQL.String() //=> SELECT * FROM users WHERE id = $1 ORDER BY id stmt.Vars //=> []interface{}{1} ToSQL Returns generated SQL without executing.

GORM uses the database/sql’s argument placeholders to construct the SQL statement, which will automatically escape arguments to avoid SQL injection, but the generated SQL don’t provide the safety guarantees, please only use it for debugging.

sql := db.ToSQL(func(tx *gorm.DB) *gorm.DB { return tx.Model(&User{}).Where("id = ?", 100).Limit(10).Order("age desc").Find(&[]User{}) }) sql //=> SELECT * FROM "users" WHERE id = 100 AND "users"."deleted_at" IS NULL ORDER BY age desc LIMIT 10 Row & Rows Get result as *sql.Row

// Use GORM API build SQL row := db.Table("users").Where("name = ?", "jinzhu").Select("name", "age").Row() row.Scan(&name, &age)

// Use Raw SQL row := db.Raw("select name, age, email from users where name = ?", "jinzhu").Row() row.Scan(&name, &age, &email) Get result as *sql.Rows

// Use GORM API build SQL rows, err := db.Model(&User{}).Where("name = ?", "jinzhu").Select("name, age, email").Rows() defer rows.Close() for rows.Next() { rows.Scan(&name, &age, &email)

// do something }

// Raw SQL rows, err := db.Raw("select name, age, email from users where name = ?", "jinzhu").Rows() defer rows.Close() for rows.Next() { rows.Scan(&name, &age, &email)

// do something } Checkout FindInBatches for how to query and process records in batch Checkout Group Conditions for how to build complicated SQL Query

Scan *sql.Rows into struct Use ScanRows to scan a row into a struct, for example:

rows, err := db.Model(&User{}).Where("name = ?", "jinzhu").Select("name, age, email").Rows() // (*sql.Rows, error) defer rows.Close()

var user User for rows.Next() { // ScanRows scan a row into user db.ScanRows(rows, &user)

// do something } Connection Run mutliple SQL in same db tcp connection (not in a transaction)

db.Connection(func(tx *gorm.DB) error { tx.Exec("SET my.role = ?", "admin")

tx.First(&User{}) }) Advanced Clauses GORM uses SQL builder generates SQL internally, for each operation, GORM creates a *gorm.Statement object, all GORM APIs add/change Clause for the Statement, at last, GORM generated SQL based on those clauses

For example, when querying with First, it adds the following clauses to the Statement

var limit = 1 clause.Select{Columns: []clause.Column{{Name: "*"}}} clause.From{Tables: []clause.Table{{Name: clause.CurrentTable}}} clause.Limit{Limit: &limit} clause.OrderBy{Columns: []clause.OrderByColumn{ { Column: clause.Column{ Table: clause.CurrentTable, Name: clause.PrimaryKey, }, }, }} Then GORM build finally querying SQL in the Query callbacks like:

Statement.Build("SELECT", "FROM", "WHERE", "GROUP BY", "ORDER BY", "LIMIT", "FOR") Which generate SQL:

SELECT * FROM users ORDER BY users.id LIMIT 1 You can define your own Clause and use it with GORM, it needs to implements Interface

Check out examples for reference

Clause Builder For different databases, Clauses may generate different SQL, for example:

db.Offset(10).Limit(5).Find(&users) // Generated for SQL Server // SELECT _ FROM "users" OFFSET 10 ROW FETCH NEXT 5 ROWS ONLY // Generated for MySQL // SELECT _ FROM users LIMIT 5 OFFSET 10 Which is supported because GORM allows database driver register Clause Builder to replace the default one, take the Limit as example

Clause Options GORM defined Many Clauses, and some clauses provide advanced options can be used for your application

Although most of them are rarely used, if you find GORM public API can’t match your requirements, may be good to check them out, for example:

db.Clauses(clause.Insert{Modifier: "IGNORE"}).Create(&user) // INSERT IGNORE INTO users (name,age...) VALUES ("jinzhu",18...); StatementModifier GORM provides interface StatementModifier allows you modify statement to match your requirements, take Hints as example

import "gorm.io/hints"

db.Clauses(hints.New("hint")).Find(&User{}) // SELECT _ /_+ hint */ FROM users