Help me with this outer MySql join (or join)

Question

This comes from converting MSSQL to MySql. The following is the code I'm trying to execute:

CREATE TEMPORARY TABLE PageIndex (
  IndexId int AUTO_INCREMENT NOT NULL PRIMARY KEY,
  ItemId VARCHAR(64)
);

INSERT INTO PageIndex (ItemId)
SELECT Paths.PathId
  FROM Paths,
       ((SELECT Paths.PathId
           FROM AllUsers, Paths
          WHERE Paths.ApplicationId = @ApplicationId
            AND AllUsers.PathId = Paths.PathId
            AND (@Path IS NULL
                OR Paths.LoweredPath LIKE LOWER(@Path))) AS SharedDataPerPath
          UNION -- This used to be a FULL OUTER JOIN but MySQL doesnt support that.
        (SELECT DISTINCT Paths.PathId
           FROM PerUser, Paths
          WHERE Paths.ApplicationId = @ApplicationId
            AND PerUser.PathId = Paths.PathId
            AND (@Path IS NULL
                OR Paths.LoweredPath LIKE LOWER(@Path))) AS UserDataPerPath
             ON SharedDataPerPath.PathId = UserDataPerPath.PathId)
          WHERE Paths.PathId = SharedDataPerPath.PathId OR Paths.PathId = UserDataPerPath.PathId
          ORDER BY Paths.Path ASC;

Suppose that there are any variables. Where this breaks down is in the "As SharedDataPerPath" part, so I assume I am imposing a select statement so that you can access it, since the table is not supported in MySQL? If the table layout helps, answer with a comment and I will add this to the question.

Thanks in advance!

Answer 1

-- Assuming these are defined in your store procedure
DECLARE @ApplicationId VARCHAR(64);
DECLARE @Path VARCHAR(256);
SET @ApplicationId = NULL;
Set @Path = NULL;

CREATE TEMPORARY TABLE SharedDataPerPath
(
  PathId VARCHAR(256)
);

CREATE TABLE UserDataPerPath
(
  PathId VARCHAR(256)
);

-- Do this instead of aliasing a select statment 'AS SharedDataPerPath'
INSERT INTO SharedDataPerPath
SELECT Paths.PathId
  FROM aspnet_PersonalizationAllUsers AllUsers, aspnet_Paths Paths
 WHERE Paths.ApplicationId = @ApplicationId
   AND AllUsers.PathId = Paths.PathId
   AND (@Path IS NULL OR Paths.LoweredPath LIKE LOWER(@Path));

-- Do this instead of aliasing a select statement 'AS UserDataPerPath'
INSERT INTO UserDataPerPath
SELECT DISTINCT Paths.PathId
  FROM aspnet_PersonalizationPerUser PerUser, aspnet_Paths Paths
 WHERE Paths.ApplicationId = @ApplicationId
   AND PerUser.PathId = Paths.PathId
   AND (@Path IS NULL OR Paths.LoweredPath LIKE LOWER(@Path));

-- This is how I would do my 'FULL OUTER JOIN'
SELECT Paths.PathId
    FROM `wppi_net_db`.`aspnet_Paths` Paths,
         (SELECT *
            FROM SharedDataPerPath AS s
            LEFT OUTER JOIN UserDataPerPath AS u
              ON s.PathID = u.PathID
           UNION -- OR UNION ALL see: http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/
          SELECT *
            FROM SharedDataPerPath AS s
           RIGHT OUTER JOIN UserDataPerPath AS u
              ON s.PathID = u.PathID) AS DataPerPaths
   WHERE Paths.PathId = DataPerPaths.PathId
   ORDER BY Paths.Path ASC;

-- At some point you need to drop your temp tables
DROP TEMPORARY TABLE SharedDataPerPath;
DROP TEMPORARY TABLE UserDataPerPath;

Answer 2

A FULL OUTER JOIN UNION LEFT JOIN, RIGHT JOIN. .. , , , . , . , .

, FULL OUTER JOIN UNION JOIN , . , UNION ed , WHERE, .

Answer 3

, , , , , , . , .

• Swap the table sources on the columns you use for joining from one selection to another to account for the NULLs generated by external joins.

• Add the COALESCE functions to your "fixed columns", which can also be returned as NULLs created by external joins.

Example:

SELECT
`Wins_VW`.`Year`,
`Wins_VW`.`Period`,
COALESCE(`Wins_VW`.`Wins`,0) as Wins,
COALESCE(`Leads_VW`.`Leads`,0) as Leads
FROM `Wins_VW` LEFT OUTER JOIN `Leads_VW`
ON( `Wins_VW`.`Year` = `Leads_VW`.`Year`
AND `Wins_VW`.`Period` = `Leads_VW`.`Period`)

UNION

SELECT
`Leads_VW`.`Year`,
`Leads_VW`.`Period`,
COALESCE(`Wins_VW`.`Wins`,0) as Wins,
COALESCE(`Leads_VW`.`Leads`,0) as Leads
FROM `Wins_VW` RIGHT OUTER JOIN `Leads_VW`
ON( `Wins_VW`.`Year` = `Leads_VW`.`Year`
AND `Wins_VW`.`Period` = `Leads_VW`.`Period`)