SQL SELECT语句，用于从具有外键和关联关系的多个表中提取数据

Question

I have the following tables:

1. Universities( iduni, uniname )
2. Campuses( idcampus, iduni, campusname, campusaddress )
3. Projects( idproject, idcampus, projectname )
4. IndustryCode( idindustrycode, codenumber, description )
5. Specialization( idspec, specname )

The following are the associative tables for some of the above listed tables

1. CampusSpecialization( idcampus, idspec )
2. ProjectSpecialization( idproject, idSpec )
3. ProjectIndustryCode( idproject,idindustrycode )

And I want to generate XML file with the following structure via PHP, but can't figure out the SELECT statement to pull the data from the database. The data being the campuses, universities, projects, industry codes and specializations for each project so that when I can filter the results in my small application later on based on this interconnected data.

    <items>
        <item>
            <campus campusname="$CAMPUSNAME" uniname="$UNINAME" campusaddress="$CAMPUSADDRESS">
                <projects>
                    <project>
                        <name>$PROJECTNAME</name>
                        <specs>
                            <spec>$SPECNAME1</spec>
                            <spec>$SPECNAME2</spec>
                            ...
                        </specs>
                        <industries>
                            <industry>$CODENUMBER1</industry>
                            <industry>$CODENUMBER2</industry>
                            ...
                        </industries>
                    </project>
...
                </projects>
            </campus>
        </item>
        <item>
            <campus ... >
                <projects>
                    <project ... >
                        ...
                    </project>
            </campus>
    </items>

This is my SQL statment so far:

SELECT
  campusname, 
  specname,
  projectname
FROM
  Specialization,Projects
  JOIN CampusSpecialization ON CampusSpecialization.idspec = Specialization.idspec
  JOIN Campuses ON CampusSpecialization.idcampus = Campuses.idcampus
  JOIN ProjectSpecialization ON ProjectSpecialization.idspec = Specialization.idspec

EDIT:

Projects may have one or more codes and industries.

Answer 1

try this:

SELECT c.campusname,u.uniname,c.campusaddress, s.specname, ic.codenumber, p.projectname
FROM campuses c
INNER JOIN universities u ON u.iduni = c.iduni
INNER JOIN camousspecialization cs ON cs.idcampus = c.idcampus
INNER JOIN speicialization s ON s.idspec = cs.idspec
INNER JOIN projectspecialization ps ON ps.idproject = s.idspec
INNER JOIN projectindustrycode pi On pi.idproject = ps.idproject
INNER JOIN industrycode ic on ic.industrycode = pi.industrycode
INNER JOIN projects p on p.idproject = ps.idproject 

Answer 2

Not tested, but this should pull all campuses with projects, and the project's codeNumber and specName.

Note, I am not completely sure about your schema. The associative tables imply there may be multiple codes and specNames per project. Whereas the xml implies there is only one of those per project. This query will return one record for each entry in your associative tables. ie If there are three (3) specifications for "Project A", the SELECT will return three (3) records.

SELECT  c.idCampus
        , c.campusName
        , c.campusAddress
        , u.uniName
        , p.projectName
        , s.specName as ProjectSpecName
        , ic.codeNumber AS ProjectCodeNumber
FROM    Campuses c
            INNER JOIN Universities u ON u.iduni = c.iduni
            INNER JOIN Projects p ON p.idcampus = c.idcampus
            INNER JOIN ProjectSpecialization ps ON ps.idproject = p.idproject
            INNER JOIN Specialization s ON s.idspec = ps.idspec
            INNER JOIN ProjectIndustryCode pic ON pic.idproject = p.idproject
            INNER JOIN IndustryCode ic ON ic.idindustrycode = pic.idindustrycode

Edit: Unfortunately, I do not use php. So I do not know the best or standard way to generate xml in php. You could possibly use group_concat in your SELECT to return a concatenated list of the codes and names for each project. Then split those string into an array in php and use the array count to generate the desired number of xml elements.

SELECT  c.idCampus
        , c.campusName
        , c.campusAddress
        , u.uniName
        , p.projectName
        , GROUP_CONCAT(s.specName SEPARATOR '|') as SpecNameList
        , GROUP_CONCAT(ic.codeNumber SEPARATOR '|') AS CodeNumberList
       ...