mysql left join selecting only highest from left table - mysql

Question

I've tried adapting solutions from SELECT biggest row from a LEFT JOIN and mysql: How to INNER JOIN a table but limit join to 1 result with the highest vote or count? but can't figure it out.
I'm joining two tables, the one being joined has two duplicate rows, the only difference is field 'page_id' - I want the one with the highest page_id number
tagID page_id companyID teamID companyID
1510 289 16 9 16
1418 163 16 9 16
(there are other text fields I want but these aren't used in matching so excluded them here)
My original query was
SELECT * FROM `cms_company_tags`
LEFT JOIN `cms_companies` ON `cms_companies`.`companyID`=`cms_company_tags`.`companyID`
WHERE `cms_company_tags`.`teamID`='9'
ORDER BY `cms_companies`.`companyName` ASC
which selected both rows
tagID page_id companyID teamID newsID companyID
1510 289 16 9 0 16
1418 163 16 9 0 16
I've tried
Select cms_company_tags.*, cms_companies.*
From cms_company_tags
Left Join cms_companies
On cms_companies.companyID = cms_company_tags.companyID
And cms_companies.page_id = (
Select Max( t.page_id )
From cms_companies As t
Where t.page_id = cms_company_tags.page_id
GROUP BY cms_company_tags.tagID
ORDER BY cms_company_tags.tagID DESC
)
WHERE `cms_company_tags`.`teamID`='9'
ORDER BY `cms_companies`.`companyName` ASC
and
SELECT * FROM `cms_company_tags`
LEFT JOIN `cms_companies` ON `cms_companies`.`companyID`=`cms_company_tags`.`companyID`
AND `cms_companies`.`page_id` = (SELECT MAX(page_id) AS pageID from `cms_companies` where `cms_companies`.`page_id` = `cms_company_tags`.`page_id`)
WHERE `cms_company_tags`.`teamID`='9'
ORDER BY `cms_companies`.`companyName` ASC
Both of which return
tagID page_id companyID teamID newsID companyID
1510 289 16 9 0 NULL
1418 163 16 9 0 16
With all the text fields being NULL too
I want the only the highest page_id. I could live with a duplicate row with NULL for the text field if it were the highest one and not the lowest one as I'm getting how.
EDIT:
Although this solution from returns the LOWEST page_id it does filter out the duplicate, luckily for me the text parts I need weren't affected. Posting here in the hope this partial solution is useful to someone
SELECT *
FROM cms_company_tags
INNER JOIN (
SELECT companyID, companyName, page_path, MAX(page_id) AS MaxPageID
FROM cms_companies
GROUP BY cms_companies.page_id
) MaxPages ON
cms_company_tags.companyID = MaxPages.companyID AND
cms_company_tags.page_id = MaxPages.MaxPageID AND
cms_company_tags.teamID = 9
ORDER BY MaxPages.companyName ASC

Answer 1

First off: why are you joining? You're only selecting from the left table, so left joining to another table won't affect the results. An inner join would affect results (by omitting companies that don't exist in cms_companies), but a left join won't.
At any rate, to get the highest page ID by company ID and team ID, try this:
SELECT companyID, teamID, MAX(page_ID)
FROM cms_company_tags
GROUP BY companyID, teamID
Then to get the unique rows from cms_company_tags, just join to the "highest by ID" as a subquery:
SELECT tagID, page_id, companyID, teamID
FROM cms_company_tags
INNER JOIN (
SELECT companyID, teamID, MAX(page_ID) AS MaxPageID
FROM cms_company_tags
GROUP BY companyID, teamID
) MaxPages ON
cms_company_tags.companyID = MaxPages.companyID AND
cms_company_tags.teamID = MaxPages.teamID
cms_company_tags.page_id = MaxPages.MaxPageID
This query returns the max page and other information for all companies/teams. You can add WHERE teamID = 9 to limit results to team 9.

Answer 2

Have you used ROW_NUMBER windowed function in sql server.
May be what you are looking is this:
select * from(
select *,row_number()over(partition by companyid, teamid, newsid, companyid order by page_id desc) as num
from 'cms_company_tags'
left join 'cms_companies' on 'cms_companies'.'companyID'='cms_company_tags'.'companyID'
where 'cms_company_tags'.'teamID'='9'
)tbl
where tbl.num =1