查询以根据一个字段的最大值和另一字段的特定值查找数据

Question

My SQL skills are minimal so I hope someone will help me. I am writing a PHP script in which I need to do some SQL queries:

I have a table called product_status, which has three 4 columns: id prod_id status_date status_code

So if we consider a product with id 1000, the table would have entries like:

id    prod_id   status_date            status_code  
1     1000      2015-09-01 08:20:35    100
2     1000      2015-09-01 09:22:40    200
3     1000      2015-09-01 09:35:51    300
4     1000      2015-09-01 09:42:55    400

Now, considering that say 300 is the status code for 'out-of-stock'. I want to write a query, where for a given date, it gives me all products that were NOT out-of-stock at the end of that day. In other words it should give me products 1000 if I query it for date '2015-09-01' since 300 is NOT the LAST entry for that product for that date in this table.

I am unable to write a query that works for this :( My query is:

select prod_id, status from product_status
where status_code != 300
group by prod_id, status
having date(max(status_date)) = '2015-09-01'

This returns me products which have statuses other than 300 as final status for the given day as well... Can anyone help correct my SQL?

Answer 1

you want to filter by status, not group by it in this query, like this:

select prod_id, status from product_status
where status_code != 300
group by prod_id
having date(max(status_date)) = '2015-09-01'

Answer 2

Try this query

SELECT prod_id, 
SUBSTRING_INDEX(GROUP_CONCAT(status_date ORDER BY status_date DESC), ',', 1) as max_date, 
SUBSTRING_INDEX(GROUP_CONCAT(status_code ORDER BY status_date DESC), ',', 1) as recent_code
FROM product_status
GROUP BY prod_id
HAVING recent_code != '300' AND date(max_date) = '2015-09-01'