genmai.go
func (c *Condition) Between(from, to interface{}) *Condition {
	return c.appendQuery(100, Between, &between{from, to})
}
func (c *Condition) Between(from, to interface{}) *Condition {
	return c.appendQuery(100, Between, &between{from, to})
}
// Between adds "BETWEEN ... AND ..." clause to the Condition and returns it for method chain.