genmai.go
func (c *Condition) Limit(lim int) *Condition {
	return c.appendQuery(500, Limit, lim)
}
func (c *Condition) Limit(lim int) *Condition {
	return c.appendQuery(500, Limit, lim)
}
// Limit adds "LIMIT" clause to the Condition and returns it for method chain.