table

type Column struct {
	Table              *Table
	Type               reflect.Type
	Index              int
	Field              string
	Name               string // many_to_many is table name
	Relation           int
	RelationType       reflect.Type
	RelationTable      *Table
	Valuer, Scanner    bool
	Getter, Setter     int
	GetType, SetType   reflect.Type
	GetError, SetError bool
	GetPointer         bool
	Encoding           string // json or gob
	// many_to_many only
	NameLeft, NameRight       string
	ThroughTable              *Table
	ThroughLeft, ThroughRight *Column
}

type Columner interface {
	// field name
	// if relation's struct name, primary key field name, table name and primary key column name
	// return column name
	ColumnName(...string) string
}

type Table struct {
	Type          reflect.Type
	Value         reflect.Value
	Name          string
	Columns       []*Column
	FieldMap      map[string]*Column
	ColumnMap     map[string]*Column // no many relation columns
	PrimaryKey    *Column
	AutoIncrement *Column
	AutoNowAdd    *Column
	AutoNow       *Column
}

type Tabler interface {
	// return table name
	TableName() string
}

type Througher interface {
	// field name
	// return through table, left field name, right field name
	ThroughTable(string) (interface{}, string, string)
}