MYSQL-如果当前值为零，如何获取上一行的值

Question

I have a table called value_record like below

id | record_id | value | serverTime
1  |     20    |   0   |  2016-04-19 04:51:16
2  |     20    |   0   |  2016-04-19 04:40:19
3  |     20    |   0   |  2016-04-19 04:27:34
4  |     20    |   70  |  2016-04-19 04:14:24
5  |     20    |   50  |  2016-04-19 04:02:21

..

select value from value_record
where record_id in(20) 
order by serverTime desc limit 1;

output :

0

but expected output is:

70

it means if current value is zero then query go back previous row where not zero and display the non zero value.

How to achieve this in mysql?

Answer 1

You need to filter values different than 0 and you don't need IN clause:

SELECT
    `value`
FROM
    value_record
WHERE
    record_id = 20
    AND `value` > 0
ORDER BY
    serverTime DESC
LIMIT 1;

Answer 2

SELECT value 
FROM value_record 
WHERE record_id IN(20) 
AND value > 0 
ORDER BY serverTime LIMIT 1;