Question

I have the following sql which returns Projects and related Contractors as well as document size info from three different tables. The sequence is: First Contractors are entered in the system, then Projects are entered for each Contractors, during with document sizes (sheets) are entered. So far so good: The following sql returns all projects along with appropriate Contractors and Sheets fine:

SELECT 
   dbo.generalcontractors.name,
   dbo.Projects.*,
   dbo.sheets.sheetsize,
   dbo.sheets.sheetid
FROM 
   dbo.generalcontractors 
INNER JOIN dbo.Projects ON (dbo.generalcontractors.uid = dbo.Projects.generalcontractorid)
INNER JOIN dbo.sheets ON (dbo.Projects.sheetid = dbo.sheets.sheetid) 
ORDER BY 
    dbo.Projects.projectdate DESC

Now, what needs to happen is that documents for individual projects are entered in a ProjectDocuments table. I have the following code which checks to see documents exist in the ProjectsDocuments table and return appropriate values; currently, the project id is hard-coded and it work.

Question is: how can I combine the following sql into the sql above? I am looking for one query result which will show any matching rows from the ProjectsDocument table and if no matching then will show ‘Not Found’.

This is for SQL Server 2005.

Thanks!

IF (SELECT COUNT(*) FROM dbo.projectsdocuments, dbo.Projects 
    WHERE projectsdocuments.projectid = Projects.projectid 
    AND Projects.projectid = 5) > 0 
    SELECT * 
    FROM projectsdocuments 
ELSE 
    SELECT 'Not Found' AS HighPrice

Answer 1

One option would be to just simply add the ProjectDocuments table to your query, using a LEFT OUTER JOIN.

If there are no matching rows in the ProjectDocuments table – then all columns from that table will be NULL – so capturing one of the columns and using the ISNULL(<colname>, 'Not Found') construction, you’d be displaying ‘Not Found’ when no values have been found in ProjectDocuments:

SELECT 
   gc.name,
   pr.ProjectDate, pr.Column1, pr.Column2, ....., pr.ColumnN,
   s.sheetsize,
   s.sheetid,
   ISNULL(pd.Name, 'Not Found') AS 'ProjectDocumentName',
   pd.Column1, ..., pd.ColumnN
FROM 
   dbo.GeneralContractors gc 
INNER JOIN 
   dbo.Projects pr ON gc.uid = pr.GeneralContractorID
INNER JOIN 
   dbo.Sheets s ON pr.SheetID = s.SheetID
LEFT OUTER JOIN
   dbo.ProjectsDocuments pd ON pr.ProjectID = pd.ProjectID
ORDER BY 
    pr.ProjectDate DESC

Two things I’d recommend doing:

• use meaningful table aliases (like gc for GeneralContractor, pr for Project and so forth) – it makes reading the queries just soooo much easier….

• explicitly specify the columns you want to to retrieve from the tables – that prevents unwanted surprises when suddenly your table has five BLOB columns more that get returned – even though you don’t need them!