Getting rows from multiple table - PHP and loop - php

Question

I'm trying to search for all the parent category of child category from 2 tables
Sample database
table1 table2
+------------+-------------+ +------------+-------------+
|Categ_name |Categ_parent | |Temp_name |Temp_parent |
+------------+-------------+ +------------+-------------+
|Items |0 | |Cookware |Kitchen |
|House |Item | |Utensils |Cookware |
|Car |Item | +------------+-------------+
|Kitchen |House |
|Living Room |House |
|Appliance |Living Room |
+------------+-------------+
if I search for 'Utensils', hoping to get
Categories :
Cookware
Kitchen
House
Items
as a result but I'm a little confused with SQL.
$i='Utensils';
while($i!='0'){
$sql="SELECT m.Categ_parent AS parent,t.Temp_parent AS parent, FROM table1 AS m,table2 AS t WHERE m.Categ_name='".$i."' OR t.Temp_name='".$i."' LIMIT 1";
$result=mysqli_query($con,$sql);
$row=mysqli_fetch_array($result);
$i=$row['parent'];
echo $i;
}
I'm not getting any result or error from this code

Answer 1

For repeatedly accessing the same table, you might be better off using a stored procedure.
## Create a view so that we can work more easily with the tables
create view items as select Categ_name as name, Categ_parent as parent from table1
union (select Temp_name as name, Temp_parent as parent from table2);
name parent
-------------------------
Item 0
House Item
Car Item
Kitchen House
Living Room House
Appliance Living Room
Cookware Kitchen
Utensils Cookware
DROP PROCEDURE IF EXISTS selectName;
CREATE PROCEDURE selectName(IN currentName VARCHAR(100))
BEGIN
drop temporary table if exists tmp_results;
create temporary table tmp_results (
name varchar(100)
);
while (exists(select parent from items where name = currentName)) DO
select parent into currentName from items where name = currentName;
insert into tmp_results select currentName;
END WHILE;
select * from tmp_results;
END;
To use this procedure:
call selectName('Utensils');
Cookware
Kitchen
House
Item
0
PHP code to initialize database (run the statements only ONCE to create the view and stored procedure):
// create view
$mysqli->query("
drop view if exists viewItems;
create view viewItems as select Categ_name as name, Categ_parent as parent from table1
union (select Temp_name as name, Temp_parent as parent from table2)";
");
// create stored procedure
$mysqli->query("
DROP PROCEDURE IF EXISTS selectParents;
CREATE PROCEDURE selectParents(IN currentName VARCHAR(100))
BEGIN
drop temporary table if exists tmp_results;
create temporary table tmp_results (
name varchar(100)
);
while (exists(select parent from viewItems where name = currentName)) DO
select parent into currentName from viewItems where name = currentName;
insert into tmp_results select currentName;
END WHILE;
select * from tmp_results;
END"
);
PHP code to query
$name = mysqli_real_escape_string($name);
$results = $mysqli->query("CALL selectParents($name)");

Answer 2

at first the SQL you wrote has an error which is the "," before "from ...".
I suggest using UNION instead of the current SQL command. The current command will mix two parent values and one of which may not be right.
Try the following solution, which works good on my computer:
$i='Utensils';
while($i!='0'){
$sql="(SELECT Categ_parent as parent from table1 WHERE Categ_name='".$i."')
UNION
(SELECT Temp_parent as parent from table2 where Temp_name='".$i."')";
$result = mysqli_query($con,$sql);
if($result && mysqli_num_rows($result)){
$row = mysqli_fetch_array($result);
$i = $row["parent"];
}
else{
$i = '0';
}
echo $i."<br>";
}