Abusing language features for fun and profit, query provides a different take for querying SQL databases in Go keeping SQL front and centre, but using language constructs to generate the SQL.
query provides a set of helper functions to assist with querying a SQL database. The caller is able to prepare SQL queries through defining a Go struct which doubles as the scan target when retrieving a SQL result set. The results may then be transformed into the application domain model in a type-safe manner, or the original query struct can be used by the application using the Ident function. This reduces the load on the developer to have to define a query, define SQL-safe variables to scan into, and convert the results into a usable model by combining the first and second operation.
type User struct {
ID int
Name string
}
func FindUser(ctx context.Context, db *sql.DB, userID int) (User, error) {
type users struct {
query.Conditions `q:"id = $1"`
ID int
Name string
}
return query.One(ctx, db, func(row users) User {
return User{ID: row.ID, Name: row.Name}
}, userID)
}
type User struct {
ID int
Name string
}
func FindUsers(ctx context.Context, db *sql.DB, limit, offset int) ([]User, error) {
type users struct {
query.Limit `q:"$1"`
query.Offset `q:"$2"`
ID int
Name string
}
return query.All(ctx, db, func(row users) User {
return User{ID: row.ID, Name: row.Name}
}, limit, offset)
}
type User struct {
ID int
Name string
Addresses []Address
}
type Address struct {
ID int
City string
State string
}
func FindUser(ctx context.Context, db *sql.DB, userID int) (User, error) {
return query.One(ctx, db, func(u userQuery) User {
user := User{
ID: u.ID,
Name: u.Name,
Addresses: make([]Address, len(u.Addresses)),
}
for i, addr := range u.Addresses {
user.Addresses[i] = Address{
ID: addr.ID,
City: addr.City,
State: addr.State,
}
}
return user
}, userID)
}
type usersQuery struct {
query.Table `q:"users"`
ID int
Name string
Addresses []struct {
ID int
City string
State string
} `q:"users.address_id = addresses.id"`
}
type userQuery struct {
query.Conditions `q:"users.id = $1"`
usersQuery
}
While query works with standard database/sql database/transaction handles, additional features can be unlocked by opening the database using query's Open function. The following options are available:
The Namer configuration open allows the caller to specify an object that implements the Namer interface to provide custom query naming rules. This allows customization for databases that do not match the default standard namer conventions used by query.
The Logger holds a function that accepts a query and arguments which is called when a query is executed. This can be used to help with debugging or to keep tabs on what queries are being executed.
db, err := query.Open("sqlite3", "myfile.db", &query.Options{
Namer: myNamer,
Logger: func(query string, args []any) {
fmt.Println(query, args)
},
})
type users struct {
ID int `q:"id"`
Name sql.NullString `q:"name"`
}
// SELECT id, name FROM users
type users struct {
query.Table `q:"user"`
query.Conditions `q:"id = ?"`
query.GroupBy `q:"id, name"`
query.OrderBy `q:"name DESC"`
query.Limit `q:"10"`
query.Offset `q:"?"`
ID int `q:"id"`
Name sql.NullString `q:"name"`
}
// SELECT id, name FROM user WHERE id = ?
// GROUP BY id, name ORDER BY name DESC
// LIMIT 10 OFFSET ?
type users struct {
Count int `q:"COUNT(*)"`
}
// SELECT COUNT(*) FROM users
type usersQuery struct {
query.Table `q:"users"`
ID int
Name string
}
type usersByIDQuery struct {
query.Conditions `q:"id = ?"`
usersQuery
}
// SELECT id, name FROM users WHERE id = ?
type usersQuery struct {
query.Table `q:"users"`
ID int
Name string
Addresses struct {
City string
} `q:"users.address_id = addresses.id`
}
// SELECT users.id, users.name, addresses.city FROM users INNER JOIN addresses ON users.address_id = addresses.id
type usersQuery struct {
query.Table `q:"users"`
ID int
Name string
Addresses struct {
query.LeftJoin
City sql.NullString
} `q:"users.address_id = addresses.id`
}
// SELECT users.id, users.name, addresses.city FROM users LEFT JOIN addresses ON users.address_id = addresses.id
type usersQuery struct {
query.Table `q:"users"`
ID int
Name string
Addresses []struct {
City string
} `q:"users.address_id = addresses.id`
}
// SELECT users.id, users.name, addresses.city FROM users INNER JOIN addresses ON users.address_id = addresses.id