mysql decimal类型的精度问题

若是是小数精度是16位，计算的时候要特别当心，好比balance和locked的类型是decimal(32,16)，下面的sql就会有精度问题：

UPDATE accounts SET balance = balance - '2.2345678977654321', locked = locked + '2.2345678977654321' WHERE accounts.id = 1

改为下面的就能够了

UPDATE accounts SET balance = balance - cast('2.2345678977654321' as decimal(32,16)), locked = locked + cast('2.2345678977654321' as decimal(32,16))  WHERE accounts.id = 1

更新：

问题出在用了字符串上，改为以下也就正确了：

UPDATE accounts SET balance = balance - 2.2345678977654321, locked = locked + 2.2345678977654321 WHERE accounts.id = 1