在Mysql中从右表加入四个没有重复的表？

Question

I have to fetch data of all users from database, the database structure is as following, which is just few columns from each table, but enough for proof of concept

 CREATE TABLE `tblpersonal` (
  `intCompNo` int(11) NOT NULL,
  `strName` varchar(500) COLLATE utf8_bin NOT NULL)


CREATE TABLE `tbledu` (
  `intEduId` int(11) NOT NULL AUTO_INCREMENT,
  `intCompNo` int(11) NOT NULL,
  `intEduType` varchar(64) COLLATE utf8_bin DEFAULT NULL)


CREATE TABLE `tbltrain` (
  `intTrainId` int(5) NOT NULL AUTO_INCREMENT,
  `intCompNo` int(5) NOT NULL,
  `strCourseName` varchar(300) COLLATE utf8_bin NOT NULL)

CREATE TABLE `tblrequests` (
  `intReqId` int(11) NOT NULL AUTO_INCREMENT,
  `intCompNo` int(11) NOT NULL,
  `strNotes` varchar(512) COLLATE utf8_bin NOT NULL,
  `dateOfSubmit` datetime NOT NULL,
  PRIMARY KEY (`intReqId`))

now I am running the query below to get the person name, IDs of his education and ID's of his training, and the last request number he has sent

SELECT tblpersonal.intCompNo, tblpersonal.strName, tbltrain.intTrainId, tbledu.intEduId, tblrequests.intReqId

FROM tblpersonal

LEFT JOIN tblrequests ON tblpersonal.intCompNo = tblrequests.intCompNo

AND tblrequests.intReqId = (SELECT MAX(req.intReqId) FROM tblrequests AS req WHERE req.intCompNo = tblpersonal.intCompNo)

LEFT JOIN tbltrain ON tblpersonal.intCompNo = tbltrain.intCompNo

LEFT JOIN tbledu ON tblpersonal.intCompNo = tbledu.intCompNo

WHERE tblrequests.intReqId IS NOT NULL

AND tblpersonal.intCompNo = 12368

GROUP BY tblpersonal.intCompNo, tbltrain.intTrainId, tbledu.intEduId

ORDER BY tblpersonal.intCompNo, tbledu.intEduId, tbltrain.intTrainid;

the problem is that I have Cartesian product as a result, shows result for only one employee as below

+-----------+--------------------------+------------+----------+----------+
| intCompNo | strName                  | intTrainId | intEduId | intReqId |
+-----------+--------------------------+------------+----------+----------+
|     12368 | ????? ???? ???? ???????? |       5194 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5203 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5575 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5580 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5585 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5591 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5636 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5666 |      107 |      388 |
|     12368 | ????? ???? ???? ???????? |       5676 |      107 |      388 |

How can I get employee data with all his training and education without duplicates

Running Example of Database can be found below

Answer 1

If you don't mind a bit of string aggregation

SELECT
 tblpersonal.intCompNo
,tblpersonal.strName
,GROUP_CONCAT(DISTINCT tblrequests.intReqId ORDER BY tblrequests.intReqId SEPARATOR ', ') AS intReqIdList
,GROUP_CONCAT(DISTINCT tbledu.intEduId ORDER BY tbledu.intEduId SEPARATOR ', ') AS intEduIdList
,GROUP_CONCAT(DISTINCT tbltrain.intTrainId ORDER BY tbltrain.intTrainId SEPARATOR ', ') AS intTrainIdList
,COUNT(DISTINCT tbltrain.intTrainId) AS intTrainIds
FROM tblpersonal
INNER JOIN tblrequests
  ON tblrequests.intCompNo = tblpersonal.intCompNo
 AND tblrequests.intReqId = (SELECT MAX(req.intReqId) FROM tblrequests AS req WHERE req.intCompNo = tblpersonal.intCompNo)
LEFT JOIN tbltrain
  ON tbltrain.intCompNo = tblpersonal.intCompNo
LEFT JOIN tbledu
  ON tbledu.intCompNo = tblpersonal.intCompNo
WHERE tblpersonal.intCompNo = 12368
GROUP BY
 tblpersonal.intCompNo
,tblpersonal.strName
ORDER BY tblpersonal.intCompNo;

Result:

\nintCompNo |  strName | intReqIdList |  intEduIdList |  intTrainIdList |  intTrainIds\n--------: |  :-------- |  :----------- |  :----------- |  :--------------------------------------------------------------------------------------------------------------------------------------------- |  ----------: \n    12368 |  TEST_USER |  213 |107, 109 |  5194, 5203, 5575, 5580, 5585, 5591, 5636, 5666, 5676, 5680, 5682, 5685, 5688, 5694, 5700, 5704, 5709, 5713, 5718, 5720, 5722, 5725, 7008, 7014 |  24 \n

A test on db<>fiddle here

Or how do you feel about uniting them?

SET @CompNo = 12368;
SELECT
 person.intCompNo
,person.strName AS PersonName
,Src.Source
,Src.SrcId
FROM
(
  SELECT req.intCompNo, 'req' AS Source, MAX(req.intReqId) AS SrcId
  FROM tblrequests req
  WHERE req.intCompNo = @CompNo
  GROUP BY req.intCompNo

  UNION ALL

  SELECT train.intCompNo, 'trn', train.intTrainId
  FROM tbltrain AS train
  WHERE train.intCompNo = @CompNo

  UNION ALL

  SELECT edu.intCompNo, 'edu', edu.intEduId
  FROM tbledu AS edu
  WHERE edu.intCompNo = @CompNo
) AS Src
INNER JOIN tblpersonal AS person
        ON Src.intCompNo = person.intCompNo
ORDER BY 
 person.intCompNo, 
 Src.Source, 
 Src.SrcId;

db<>fiddle here

Or maybe this variation of using unions?

SET @CompNo = 12368;
SELECT
 person.intCompNo
,person.strName AS PersonName
,Src.intReqId
,Src.intTrainId
,Src.intEduId
FROM
(
  SELECT req.intCompNo
  , MAX(req.intReqId) AS intReqId
  , 0 AS intTrainId
  , 0 AS intEduId
  FROM tblrequests req
  WHERE req.intCompNo = @CompNo
  GROUP BY req.intCompNo

  UNION ALL

  SELECT train.intCompNo
  , 0 AS intReqId
  , train.intTrainId
  , 0 AS intEduId
  FROM tbltrain AS train
  WHERE train.intCompNo = @CompNo

  UNION ALL

  SELECT edu.intCompNo
  , 0 AS intReqId
  , 0 AS intTrainId
  , edu.intEduId
  FROM tbledu AS edu
  WHERE edu.intCompNo = @CompNo
) AS Src
INNER JOIN tblpersonal AS person
        ON Src.intCompNo = person.intCompNo
ORDER BY 
 person.intCompNo,
 Src.intTrainId, Src.intEduId, Src.intReqId;

But perhaps you're more looking for a solution like this one that works in MySql 8.0 . It re-uses a CTE (Common Table Expression).
And uses the window function ROW_NUMBER.
Basically, it links the edu & requests on the same calculated row number of the bigger training table.

WITH PERSONAL AS
(
    SELECT intCompNo, strName
    FROM tblpersonal
    WHERE intCompNo IN (12368)
)
SELECT
 person.intCompNo
,person.strName AS PersonName
,req.intReqId
,edu.intEduId
,trn.intTrainId
FROM PERSONAL AS person
LEFT JOIN
(
  SELECT t.intCompNo, t.intTrainId
  , ROW_NUMBER() 
      OVER (PARTITION BY t.intCompNo 
                ORDER BY t.intTrainId) AS rn
  FROM tbltrain AS t
  JOIN PERSONAL p
    ON p.intCompNo = t.intCompNo
) AS trn
ON trn.intCompNo = person.intCompNo
LEFT JOIN
(
  SELECT t.intCompNo
  , MAX(t.intReqId) AS intReqId
  , 1 AS rn
  FROM tblrequests t
  JOIN PERSONAL p
    ON p.intCompNo = t.intCompNo
  GROUP BY t.intCompNo
) AS req
  ON req.intCompNo = trn.intCompNo
 AND req.rn = trn.rn
LEFT JOIN
(
  SELECT t.intCompNo, t.intEduId
  , ROW_NUMBER() 
      OVER (PARTITION BY t.intCompNo 
                ORDER BY t.intEduId) AS rn
  FROM tbledu AS t
  JOIN PERSONAL p
    ON p.intCompNo = p.intCompNo
) AS edu
  ON edu.intCompNo = trn.intCompNo
 AND edu.rn = trn.rn
ORDER BY person.intCompNo;

\nintCompNo |  PersonName | intReqId | intEduId | intTrainId\n--------: |  :--------- |  -------: |  -------: |  ---------: \n    12368 |  TEST_USER |  213 |107 |  5194 \n    12368 |  TEST_USER |  null | 109 |  5203 \n    12368 |  TEST_USER |  null | null | 5575 \n    12368 |  TEST_USER |  null | null | 5580 \n    12368 |  TEST_USER |  null | null | 5585 \n    ... \n\n

Test on db<>fiddle here

Answer 2

You seem to be after something like this, which, if not correct, at least has the appearance of a valid query.

SELECT DISTINCT p.intCompNo
              , p.strName
              , t.intTrainId
              , e.intEduId
              , r.intReqId  
           FROM tblpersonal p
           LEFT 
           JOIN tblrequests r
             ON r.intCompNo = p.intCompNo 
           JOIN 
              ( SELECT req.intCompNo
                     , MAX(req.intReqId) intreqid
                  FROM tblrequests req 
                 GROUP 
                    BY req.intCompNo 
              ) x 
             ON x.intreqid = r.intReqId 
            AND x.intCompNo = p.intCompNo)
           LEFT 
           JOIN tbltrain t 
             ON t.intCompNo = p.intCompNo 
           LEFT 
           JOIN tbledu e
             ON e.intCompNo = p.intCompNo 
          WHERE r.intReqId IS NOT NULL
            AND p.intCompNo = 12368 
          ORDER 
             BY p.intCompNo
              , e.intEduId
              , t.intTrainid;