QueryBuilder Constructs Complicate Query

QueryBuilder provides an API for convenient and fluent construction of SQL queries. It consists of a set of methods enabling developers to easily construct SQL queries without compromising readability.

It serves as an alternative to ORM. ORM is more for simple CRUD operations, whereas QueryBuilder is for complex queries with subqueries and multi-joins.

Usage example:

// User is a wrapper for result row in this example
type User struct {
    Name string
    Age  int
}
var users []User
// Get a QueryBuilder object. Takes DB driver name as parameter
// Second return value is error, ignored here
qb, _ := orm.NewQueryBuilder("mysql")
// Construct query object
qb.Select("user.name",
    "profile.age").
    From("user").
    InnerJoin("profile").On("user.id_user = profile.fk_user").
    Where("age > ?").
    OrderBy("name").Desc().
    Limit(10).Offset(0)
// export raw query string from QueryBuilder object
sql := qb.String()
// execute the raw query string
o := orm.NewOrm()
o.Raw(sql, 20).QueryRows(&users)

Full API interface:

type QueryBuilder interface {
    Select(fields ...string) QueryBuilder
    ForUpdate() QueryBuilder
    From(tables ...string) QueryBuilder
    InnerJoin(table string) QueryBuilder
    LeftJoin(table string) QueryBuilder
    RightJoin(table string) QueryBuilder
    On(cond string) QueryBuilder
    Where(cond string) QueryBuilder
    And(cond string) QueryBuilder
    Or(cond string) QueryBuilder
    In(vals ...string) QueryBuilder
    OrderBy(fields ...string) QueryBuilder
    Asc() QueryBuilder
    Desc() QueryBuilder
    Limit(limit int) QueryBuilder
    Offset(offset int) QueryBuilder
    GroupBy(fields ...string) QueryBuilder
    Having(cond string) QueryBuilder
    Update(tables ...string) QueryBuilder
    Set(kv ...string) QueryBuilder
    Delete(tables ...string) QueryBuilder
    InsertInto(table string, fields ...string) QueryBuilder
    Values(vals ...string) QueryBuilder
    Subquery(sub string, alias string) string
    String() string
}

Now we support Postgress, MySQL and TiDB.