Table tab1 (
   id     SERIAL
)

Table tab2 (
   id      SERIAL,
   tab1ID  BIGINT UNSIGNED NOT NULL,
   relData CHAR(10),
   FK tab1ID -> tab1.id
)

INSERT INTO tab2 (tab1ID, relData) 
SELECT  aa.id, bb.data
FROM  Tab1      AS aa,
     (SELECT  "data1" AS data
         UNION
      SELECT  "data2" AS data
         UNION
      SELECT  "data3" AS data
              ) AS bb
WHERE aa.id=4

------------------------------
| field1       | field2      |
------------------------------
| 123          | a           |
| 234          | b           |
| 345          | c           |
------------------------------

SELECT aa.id /*0*/, bb.data /*1*/
FROM (
    SELECT   tab1.id AS id, tab2.data AS data
UNION 
    SELECT   tab3.id AS id, tab5.info AS data
)

while($cur=mysqli_fetch_array($result)){
   echo $cur[0].', '.$cur[1].'<br>';
}

while($cur=mysqli_fetch_array($result, MYSQLI_NUM)){
   echo $cur[0].', '.$cur[1].'<br>';
}