mysql执行插入更新语句，影响条数正常应该是几条？

Question

INSERT INTO stock_spec(spec_id,unpay_num)
            (SELECT spec_id,actual_num FROM sales_trade_order 
            WHERE trade_id='194934' ) ON DUPLICATE KEY UPDATE unpay_num=unpay_num+VALUES(unpay_num);

执行如上的插入更新语句，select的值只有一条记录，执行却显示影响两条数据？这正常吗？

Answer 1

官方5.7参考手册：

If you specify ON DUPLICATE KEY UPDATE, and a row is inserted that would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row occurs. The affected-rows value per row is 1 if the row is inserted as a new row, 2 if an existing row is updated, and 0 if an existing row is set to its current values.