func (db *DB) First(dest interface{}, conds ...interface{}) (tx *DB) {
	tx = db.Limit(1).Order(clause.OrderByColumn{
		Column: clause.Column{Table: clause.CurrentTable, Name: clause.PrimaryKey},
	})
	if len(conds) > 0 {
		if exprs := tx.Statement.BuildCondition(conds[0], conds[1:]...); len(exprs) > 0 {
			tx.Statement.AddClause(clause.Where{Exprs: exprs})
		}
	}