问题
select * from table where id = 1
update table set reading =1 where id = 1
将以上2步改成独立一句sql。
答案：
update table set reading = (select reading from table t where t.id = 1)
select * from table where id = 1
update table set reading =1 where id = 1
将以上2步改成独立一句sql。
update table set reading = (select reading from table t where t.id = 1)