// Copyright 2013 - 2016 The XORM Authors. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.

/*

Package xorm is a simple and powerful ORM for Go.

Installation

Make sure you have installed Go 1.11+ and then:

    go get xorm.io/xorm

Create Engine

Firstly, we should create an engine for a database

    engine, err := xorm.NewEngine(driverName, dataSourceName)

Method NewEngine's parameters are the same as sql.Open which depend drivers' implementation.
Generally, one engine for an application is enough. You can define it as a package variable.

Raw Methods

XORM supports raw SQL execution:

1. query with a SQL string, the returned results is []map[string][]byte

    results, err := engine.Query("select * from user")

2. query with a SQL string, the returned results is []map[string]string

    results, err := engine.QueryString("select * from user")

3. query with a SQL string, the returned results is []map[string]interface{}

    results, err := engine.QueryInterface("select * from user")

4. execute with a SQL string, the returned results

    affected, err := engine.Exec("update user set .... where ...")

ORM Methods

There are 8 major ORM methods and many helpful methods to use to operate database.

1. Insert one or multiple records to database

    affected, err := engine.Insert(&struct)
    // INSERT INTO struct () values ()
    affected, err := engine.Insert(&struct1, &struct2)
    // INSERT INTO struct1 () values ()
    // INSERT INTO struct2 () values ()
    affected, err := engine.Insert(&sliceOfStruct)
    // INSERT INTO struct () values (),(),()
    affected, err := engine.Insert(&struct1, &sliceOfStruct2)
    // INSERT INTO struct1 () values ()
    // INSERT INTO struct2 () values (),(),()

2. Query one record or one variable from database

    has, err := engine.Get(&user)
    // SELECT * FROM user LIMIT 1

    var id int64
    has, err := engine.Table("user").Where("name = ?", name).Get(&id)
    // SELECT id FROM user WHERE name = ? LIMIT 1

    var id int64
    var name string
    has, err := engine.Table(&user).Cols("id", "name").Get(&id, &name)
    // SELECT id, name FROM user LIMIT 1

3. Query multiple records from database

    var sliceOfStructs []Struct
    err := engine.Find(&sliceOfStructs)
    // SELECT * FROM user

    var mapOfStructs = make(map[int64]Struct)
    err := engine.Find(&mapOfStructs)
    // SELECT * FROM user

    var int64s []int64
    err := engine.Table("user").Cols("id").Find(&int64s)
    // SELECT id FROM user

4. Query multiple records and record by record handle, there two methods, one is Iterate,
another is Rows

    err := engine.Iterate(new(User), func(i int, bean interface{}) error {
        // do something
    })
    // SELECT * FROM user

    rows, err := engine.Rows(...)
    // SELECT * FROM user
    defer rows.Close()
    bean := new(Struct)
    for rows.Next() {
        err = rows.Scan(bean)
    }

or

    rows, err := engine.Cols("name", "age").Rows(...)
    // SELECT * FROM user
    defer rows.Close()
    for rows.Next() {
        var name string
        var age int
        err = rows.Scan(&name, &age)
    }

5. Update one or more records

    affected, err := engine.ID(...).Update(&user)
    // UPDATE user SET ...

6. Delete one or more records, Delete MUST has condition

    affected, err := engine.Where(...).Delete(&user)
    // DELETE FROM user Where ...

7. Count records

    counts, err := engine.Count(&user)
    // SELECT count(*) AS total FROM user

    counts, err := engine.SQL("select count(*) FROM user").Count()
    // select count(*) FROM user

8. Sum records

    sumFloat64, err := engine.Sum(&user, "id")
    // SELECT sum(id) from user

    sumFloat64s, err := engine.Sums(&user, "id1", "id2")
    // SELECT sum(id1), sum(id2) from user

    sumInt64s, err := engine.SumsInt(&user, "id1", "id2")
    // SELECT sum(id1), sum(id2) from user

Conditions

The above 8 methods could use with condition methods chainable.
Notice: the above 8 methods should be the last chainable method.

1. ID, In

    engine.ID(1).Get(&user) // for single primary key
    // SELECT * FROM user WHERE id = 1
    engine.ID(schemas.PK{1, 2}).Get(&user) // for composite primary keys
    // SELECT * FROM user WHERE id1 = 1 AND id2 = 2
    engine.In("id", 1, 2, 3).Find(&users)
    // SELECT * FROM user WHERE id IN (1, 2, 3)
    engine.In("id", []int{1, 2, 3}).Find(&users)
    // SELECT * FROM user WHERE id IN (1, 2, 3)

2. Where, And, Or

    engine.Where().And().Or().Find()
    // SELECT * FROM user WHERE (.. AND ..) OR ...

3. OrderBy, Asc, Desc

    engine.Asc().Desc().Find()
    // SELECT * FROM user ORDER BY .. ASC, .. DESC
    engine.OrderBy().Find()
    // SELECT * FROM user ORDER BY ..

4. Limit, Top

    engine.Limit().Find()
    // SELECT * FROM user LIMIT .. OFFSET ..
    engine.Top(5).Find()
    // SELECT TOP 5 * FROM user // for mssql
    // SELECT * FROM user LIMIT .. OFFSET 0 //for other databases

5. SQL, let you custom SQL

    var users []User
    engine.SQL("select * from user").Find(&users)

6. Cols, Omit, Distinct

    var users []*User
    engine.Cols("col1, col2").Find(&users)
    // SELECT col1, col2 FROM user
    engine.Cols("col1", "col2").Where().Update(user)
    // UPDATE user set col1 = ?, col2 = ? Where ...
    engine.Omit("col1").Find(&users)
    // SELECT col2, col3 FROM user
    engine.Omit("col1").Insert(&user)
    // INSERT INTO table (non-col1) VALUES ()
    engine.Distinct("col1").Find(&users)
    // SELECT DISTINCT col1 FROM user

7. Join, GroupBy, Having

    engine.GroupBy("name").Having("name='xlw'").Find(&users)
    //SELECT * FROM user GROUP BY name HAVING name='xlw'
    engine.Join("LEFT", "userdetail", "user.id=userdetail.id").Find(&users)
    //SELECT * FROM user LEFT JOIN userdetail ON user.id=userdetail.id

Builder

xorm could work with xorm.io/builder directly.

1. With Where

    var cond = builder.Eq{"a":1, "b":2}
    engine.Where(cond).Find(&users)

2. With In

    var subQuery = builder.Select("name").From("group")
    engine.In("group_name", subQuery).Find(&users)

3. With Join

    var subQuery = builder.Select("name").From("group")
    engine.Join("INNER", subQuery, "group.id = user.group_id").Find(&users)

4. With SetExprs

    var subQuery = builder.Select("name").From("group")
    engine.ID(1).SetExprs("name", subQuery).Update(new(User))

5. With SQL

    var query = builder.Select("name").From("group")
    results, err := engine.SQL(query).Find(&groups)

6. With Query

    var query = builder.Select("name").From("group")
    results, err := engine.Query(query)
    results, err := engine.QueryString(query)
    results, err := engine.QueryInterface(query)

7. With Exec

    var query = builder.Insert("a, b").Into("table1").Select("b, c").From("table2")
    results, err := engine.Exec(query)

More usage, please visit http://xorm.io/docs
*/
package xorm