在銷量增加中犯了同樣的錯誤，一開始就認為是sql語句錯了，結果就是這個逗號被直接忽略，在service層浪費了兩個半鐘。。。感謝啊，要是沒你的提示還不知道要搞多久。

解決了，原來是沒有刪除

set?stock?=?stock?-?#{amount}，

這的逗號

### Error updating database.? Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where item_id = 5 and stock >= 1' at line 3

### The error may involve defaultParameterMap

### The error occurred while setting parameters

### SQL: update item_stock? ? ?set stock = stock - 1,? ? ?where item_id = 5 and stock >= 1

### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where item_id = 5 and stock >= 1' at line 3

; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where item_id = 5 and stock >= 1' at line 3]