Struct-based database access layer for Go

This module integrates github.com/Masterminds/squirrel query builder and github.com/jmoiron/sqlx to allow seamless operation based on field tags of row structure.

All three libraries collaborate with standard database/sql and do not take away low level control from user.

This library helps to eliminate literal string column references (e.g. "created_at") and use field references instead (e.g. rf.Ref(&row.CreatedAt) and other mapping functions).

Field tags (db by default) act as a source of truth for column names to allow better maintainability and fewer errors.

Components

Storage is a high level service that provides query building, query executing and result fetching facilities as easy to use facades.

Mapper is a lower level tool that focuses on managing squirrel query builder with row structures.

Referencer helps to build complex statements by providing fully qualified and properly escaped names for participating columns.

Simple CRUD

// Open DB connection.
s, _ := sqluct.Open(
    "postgres",
    "postgres://pqgotest:password@localhost/pqgotest?sslmode=disable",
)

ctx := context.TODO()

const tableName = "products"

type Product struct {
    ID        int       `db:"id,omitempty"`
    Title     string    `db:"title"`
    CreatedAt time.Time `db:"created_at,omitempty"`
}

// INSERT INTO products (id, title, created_at) VALUES (1, 'Apples', <now>), (2, 'Oranges', <now>)
_, err := s.Exec(ctx, s.InsertStmt(tableName, []Product{{
    ID:        1,
    Title:     "Apples",
    CreatedAt: time.Now(),
}, {
    ID:        2,
    Title:     "Oranges",
    CreatedAt: time.Now(),
},
}))
if err != nil {
    log.Fatal(err)
}

// UPDATE products SET title = 'Bananas' WHERE id = 2
_, err = s.Exec(
    ctx,
    s.UpdateStmt(tableName, Product{Title: "Bananas"}).
        Where(s.WhereEq(Product{ID: 2})),
)
if err != nil {
    log.Fatal(err)
}

var (
    result []Product
    row    Product
)
// SELECT id, title, created_at FROM products WHERE id != 3 AND created_at <= <now>
err = s.Select(ctx,
    s.SelectStmt(tableName, row).
        Where(squirrel.NotEq(s.WhereEq(Product{ID: 3}, sqluct.SkipZeroValues))).
        Where(squirrel.LtOrEq{s.Col(&row, &row.CreatedAt): time.Now()}),
    &result,
)
if err != nil {
    log.Fatal(err)
}

// You can also use generic sqluct.Get and sqluct.List in go1.18 or later.
//
// SELECT id, title, created_at FROM products WHERE id != 3 AND created_at <= <now>
result, err = sqluct.List[Product](ctx,
	s,
    s.SelectStmt(tableName, row).
        Where(squirrel.NotEq(s.WhereEq(Product{ID: 3}, sqluct.SkipZeroValues))).
        Where(squirrel.LtOrEq{s.Col(&row, &row.CreatedAt): time.Now()}),
)
if err != nil {
    log.Fatal(err)
}


// DELETE FROM products WHERE id = 2
_, err = s.Exec(ctx, s.DeleteStmt(tableName).Where(Product{ID: 2}, sqluct.SkipZeroValues))
if err != nil {
    log.Fatal(err)
}

Referencing Fields In Complex Statements

type User struct {
    ID        int    `db:"id"`
    FirstName string `db:"first_name"`
    LastName  string `db:"last_name"`
}

type DirectReport struct {
    ManagerID  int `db:"manager_id"`
    EmployeeID int `db:"employee_id"`
}

var s sqluct.Storage

rf := s.Ref()

// Add aliased tables as pointers to structs.
manager := &User{}
rf.AddTableAlias(manager, "manager")

employee := &User{}
rf.AddTableAlias(employee, "employee")

dr := &DirectReport{}
rf.AddTableAlias(dr, "dr")

// Find direct reports that share same last name and manager is not named John.
qb := squirrel.StatementBuilder.Select(rf.Fmt("%s, %s", &dr.ManagerID, &dr.EmployeeID)).
    From(rf.Fmt("%s AS %s", rf.Q("users"), manager)). // Quote literal name and alias it with registered struct pointer.
    InnerJoin(rf.Fmt("%s AS %s ON %s = %s AND %s = %s",
        rf.Q("direct_reports"), dr,
        &dr.ManagerID, &manager.ID, // Identifiers are resolved using row field pointers.
        &dr.EmployeeID, &employee.ID)).
    Where(rf.Fmt("%s = %s", &manager.LastName, &employee.LastName)).
    Where(rf.Fmt("%s != ?", &manager.FirstName), "John") // Regular binds work same way as in standard squirrel.

stmt, args, err := qb.ToSql()
if err != nil {
    log.Fatal(err)
}

fmt.Println(stmt)
fmt.Println(args)

// SELECT dr.manager_id, dr.employee_id 
// FROM users AS manager 
// INNER JOIN direct_reports AS dr ON dr.manager_id = manager.id AND dr.employee_id = employee.id 
// WHERE manager.last_name = employee.last_name AND manager.first_name != ?
//
// [John]

Omitting Zero Values

When building WHERE conditions from row structure it is often needed skip empty fields from condition.

Behavior with empty fields (zero values) can be controlled via omitempty field tag flag and sqluct.IgnoreOmitEmpty, sqluct.SkipZeroValues options.

Please check example below to learn about behavior differences.

var s sqluct.Storage

type Product struct {
    ID    int    `db:"id,omitempty"`
    Name  string `db:"name,omitempty"`
    Price int    `db:"price"`
}

query, args, err := s.SelectStmt("products", Product{}).Where(s.WhereEq(Product{
    ID:    123,
    Price: 0,
})).ToSql()
fmt.Println(query, args, err)
// This query skips `name` in where condition for its zero value and `omitempty` flag.
//   SELECT id, name, price FROM products WHERE id = $1 AND price = $2 [123 0] <nil>

query, args, err = s.SelectStmt("products", Product{}).Where(s.WhereEq(Product{
    ID:    123,
    Price: 0,
}, sqluct.IgnoreOmitEmpty)).ToSql()
fmt.Println(query, args, err)
// This query adds `name` in where condition because IgnoreOmitEmpty is applied and `omitempty` flag is ignored.
//   SELECT id, name, price FROM products WHERE id = $1 AND name = $2 AND price = $3 [123  0] <nil>

query, args, err = s.SelectStmt("products", Product{}).Where(s.WhereEq(Product{
    ID:    123,
    Price: 0,
}, sqluct.SkipZeroValues)).ToSql()
fmt.Println(query, args, err)
// This query adds skips both price and name from where condition because SkipZeroValues option is applied.
//   SELECT id, name, price FROM products WHERE id = $1 [123] <nil>