How do I convert this Access Query to mySQL query?

问题

Given a complex query for a beginner in database, how can I convert this access sql to mysql? Here is the MS ACCESS query:

SELECT tblSections.[Course Code], tblSections.Section, tblSections.Day, tblSections.[Start Time], tblSections.[End Time], tblSections.Room, tblProfessors.[Last Name], tblProfessors.[First Name], Count(tblStudentsCoursesSections.[Student ID]) AS Enrolled, ([tblCourses].[Max])-[Enrolled] AS Slots
    FROM tblCourses INNER JOIN (tblStudentsCoursesSections RIGHT JOIN (tblProfessors INNER JOIN tblSections ON tblProfessors.[ID Number] = tblSections.[Professor ID]) ON (tblStudentsCoursesSections.[Course Code] = tblSections.[Course Code]) AND (tblStudentsCoursesSections.Section = tblSections.Section)) ON tblCourses.[Course Code] = tblSections.[Course Code]
    GROUP BY tblSections.[Course Code], tblSections.Section, tblSections.Day, tblSections.[Start Time], tblSections.[End Time], tblSections.Room, tblProfessors.[Last Name], tblProfessors.[First Name], tblStudentsCoursesSections.[Course Code], tblStudentsCoursesSections.Section, tblCourses.Max
    HAVING (((tblSections.[Course Code])="SOCTEC2"));

I tried converting it by replacing [] by `` but it didn't work. Is there something wrong? This is what I inputted in the mySQL in the command line. The corresponding error is also displayed.

SELECT tblSections.`Course Code`, tblSections.Section, tblSections.Day, tblSections.`Start Time`, tblSections.`End Time`, tblSections.Room, tblProfessors.`Last Name`, tblProfessors.`First Name`, Count(tblStudentsCoursesSections.`Student ID`) AS Enrolled, (`tblCourses`.`Max`)-`Enrolled` AS Slots FROM tblCourses INNER JOIN (tblStudentsCoursesSections RIGHT JOIN (tblProfessors INNER JOIN tblSections ON tblProfessors.`ID Number` = tblSections.`Professor ID`) ON (tblStudentsCoursesSections.Section = tblSections.Section) AND (tblStudentsCoursesSections.`Course Code` = tblSections.`Course Code`)) ON tblCourses.`Course Code` = tblSections.`Course Code` GROUP BY tblSections.`Course Code`, tblSections.Section, tblSections.Day, tblSections.`Start Time`, tblSections.`End Time`, tblSections.Room, tblProfessors.`Last Name`, tblProfessors.`First Name`, tblStudentsCoursesSections.`Course Code`, tblStudentsCoursesSections.Section, tblCourses.Max HAVING (((tblSections.`Course Code`)="SOCTEC2"));

Isn't it that the count of the enrolled student will be displayed along the enrolled field?

UPDATE!!

I did what you suggested but I reverted back to HAVING keyword since WHERE results to syntax error. 

SELECT 
    tblSections.`Course Code`,
    tblSections.`Section`,
    tblSections.`Day`,
    tblSections.`Start Time`,
    tblSections.`End Time`,
    tblSections.`Room`,
    tblProfessors.`Last Name`,
    tblProfessors.`First Name`,
    COUNT(tblStudentsCoursesSections.`Student ID`) AS `Enrolled`,
    /* Since Enrolled was just defined as an alias in this scope you cannot use it 
      in the SELECT yet, but you can do the aggregate COUNT again */
    (`tblCourses`.`Max` - COUNT(tblStudentsCoursesSections.`Student ID`)) AS `Slots`
FROM
    # Order your table joins according to the pairs used in ON clauses...
    tblCourses
    INNER JOIN tblSections ON tblCourses.`Course Code` = tblSections.`Course Code`
    RIGHT JOIN tblProfessors ON tblProfessors.`ID Number` = tblSections.`Professor ID`
    INNER JOIN tblStudentsCoursesSections 
        ON ((tblStudentsCoursesSections.Section = tblSections.Section)
        AND (tblStudentsCoursesSections.`Course Code` = tblSections.`Course Code`))
GROUP BY 
    tblSections.`Course Code`,
    tblSections.`Section`,
    tblSections.`Day`,
    tblSections.`Start Time`,
    tblSections.`End Time`,
    tblSections.`Room`,
    tblProfessors.`Last Name`,
    tblProfessors.`First Name`,
    /* These are not in your SELECT list and so should probably not be in the GROUP BY
    tblStudentsCoursesSections.`Course Code`,
    tblStudentsCoursesSections.`Section`,
     Might need to group on `Slots` instead of tblCourses.Max */
    tblCourses.Max
/* This should be a WHERE rather than HAVING since it does not operate on an aggregate */
HAVING
    /* Single quotes preferred for string literals */
    tblSections.`Course Code` = 'SOCTEC2';

Unfortunately, sections with zero enrolled student does not show up. Why is that so?

回答1:

MS Access has an unusual requirement that JOINs be enclosed in a messy set of nested (). What you need to do here is unravel which tables are joined in pairs by inspecting the various ON conditions then lining them up appropriately

I've also enclosed the rest of your columns and aliases in backticks inside the GROUP BY where you had some missing.

SELECT 
    tblSections.`Course Code`,
    tblSections.`Section`,
    tblSections.`Day`,
    tblSections.`Start Time`,
    tblSections.`End Time`,
    tblSections.`Room`,
    tblProfessors.`Last Name`,
    tblProfessors.`First Name`,
    COUNT(tblStudentsCoursesSections.`Student ID`) AS `Enrolled`,
    /* Since Enrolled was just defined as an alias in this scope you cannot use it 
      in the SELECT yet, but you can do the aggregate COUNT again */
    (`tblCourses`.`Max` - COUNT(tblStudentsCoursesSections.`Student ID`)) AS `Slots`
FROM
    # Order your table joins according to the pairs used in ON clauses...
    tblCourses
    INNER JOIN tblSections ON tblCourses.`Course Code` = tblSections.`Course Code`
    /* This RIGHT JOIN is assumed to be returning all records from tblProfessors regardless
       of match in tblSections. If that is the opposite of what was intended, change to LEFT JOIN */
    RIGHT JOIN tblProfessors ON tblProfessors.`ID Number` = tblSections.`Professor ID`
    INNER JOIN tblStudentsCoursesSections 
        ON (tblStudentsCoursesSections.Section = tblSections.Section)
        AND (tblStudentsCoursesSections.`Course Code` = tblSections.`Course Code`)
/* This should be a WHERE rather than HAVING since it does not operate on an aggregate */
WHERE 
    /* Single quotes preferred for string literals */
    tblSections.`Course Code` = 'SOCTEC2';
GROUP BY 
    tblSections.`Course Code`,
    tblSections.`Section`,
    tblSections.`Day`,
    tblSections.`Start Time`,
    tblSections.`End Time`,
    tblSections.`Room`,
    tblProfessors.`Last Name`,
    tblProfessors.`First Name`,
    /* These are not in your SELECT list and so should probably not be in the GROUP BY
    tblStudentsCoursesSections.`Course Code`,
    tblStudentsCoursesSections.`Section`,
     Might need to group on `Slots` instead of tblCourses.Max */
    `Slots`

Addendum

Unfortunately, sections with zero enrolled student does not show up. Why is that so?

Since you have an INNER JOIN between tblStudentsCoursesSections and tblSections, no records in tblStudentsCoursesSections will eliminate that section from the results. To ensure the section is returned anyway, use a LEFT JOIN tblStudentsCoursesSections in place of INNER JOIN tblStudentsCoursesSections. Since tblSections is on the "left side" of the join, it will return even if there's no match.

来源：https://stackoverflow.com/questions/20661805/how-do-i-convert-this-access-query-to-mysql-query

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mysql

sql

database

ms-access

ms-access-2010