sql query select only one row from multiple rows

Question

I have this query:

SELECT p.[PostingID]
      ,[EmployerID]
      ,[JobTitle]                  
      ,pin.[IndustryID]         
FROM [Posting] p
INNER JOIN [City] c
  ON p.CityID = c.CityID
LEFT OUTER JOIN PostingIndustry pin
  ON p.PostingID = pin.PostingID
WHERE (c.CityID = @CityId OR @CityId IS NULL) 
  AND (p.StateProvinceID = @StateProvinceId OR @StateProvinceId IS NULL) 
  AND (pin.IndustryID = @IndustryId OR @IndustryId IS NULL) 
  AND 
  (
     (p.[Description] LIKE '%' + @Keyword + '%' OR @Keyword IS NULL) 
     OR (p.[JobTitle] LIKE '%' + @Keyword + '%'  OR @Keyword IS NULL)
  ) 
  AND p.StreetAddress IS NOT NULL 
  AND p.ShowOnMap = 1

Which returns results for all the pin.[IndustryID] if IndustryId is not selected or if all the industries are selected. If only one industry is selected I am getting one result which is good, but when one posting is included in multiple industries then I am getting multiple results as on the image shown below:

So for example when thats happening I want to get only one result for that posting id otherwise I am getting multiple results for one google map marker per the image below:

Is there a way how I can optimize the query above to do what I need? Thanks in advance, Laziale

Answer 1

Try using a group by clause at the end

Use MAX(IndustryId) .

Then also

GROUP BY PostingId,EmployerId,Jobtitle

Answer 2

What about selecting only the row with the smallest IndustryId:

SELECT [PostingID]
      ,[EmployerID]
      ,[JobTitle]                  
      ,MIN(pin.[IndustryID])         
FROM [Posting] p
INNER JOIN [City] c
  ON p.CityID = c.CityID
LEFT OUTER JOIN PostingIndustry pin
  ON p.PostingID = pin.PostingID
WHERE (c.CityID = @CityId OR @CityId IS NULL) 
  AND (p.StateProvinceID = @StateProvinceId OR @StateProvinceId IS NULL) 
  AND (pin.IndustryID = @IndustryId OR @IndustryId IS NULL) 
  AND 
  (
     (p.[Description] LIKE '%' + @Keyword + '%' OR @Keyword IS NULL) 
     OR (p.[JobTitle] LIKE '%' + @Keyword + '%'  OR @Keyword IS NULL)
  ) 
  AND p.StreetAddress IS NOT NULL 
  AND p.ShowOnMap = 1
GROUP BY [PostingID],[EmployerID],[JobTitle] 

Whenever you have only one, it returns that one, when you have more than one it returns only the one with the smallest IndustryId.

Answer 3

不要选择行业ID并使用“ SELECT DISTINCT ...”