Getting data from multiple tables results with less records - php

Question

I have Joomla tables (shown bellow) with some records in it (records are about companies). What I want to achieve is to get all records and group them to new table (I am using PHP for this). Problem is that there is 548 records (companies) and I got 439 records (after grouping).
Does someone knows where's the problem?
Here is database:
And here is query:
SELECT a.itemid as ID, a.title as Name, c.name as Categories, d.data_txt as Description, d.fieldid as FieldID FROM `jos_sobi2_item` as a
INNER JOIN `jos_sobi2_cat_items_relations` as b ON b.itemid=a.itemid
INNER JOIN `jos_sobi2_categories` as c ON c.catid = b.catid
INNER JOIN `jos_sobi2_fields_data`as d ON a.itemid=d.itemid

Answer 1

The issue is inner join is filtering out the records which are not in the related tables but in jos_sobi2_item
You may want to do left join something as
select
a.itemid as ID,
a.title as Name,
c.name as Categories,
d.data_txt as Description,
d.fieldid as FieldID
FROM `jos_sobi2_item` as a
left join `jos_sobi2_cat_items_relations` as b ON b.itemid=a.itemid
left join `jos_sobi2_categories` as c ON c.catid = b.catid
left join `jos_sobi2_fields_data`as d ON a.itemid=d.itemid
Here is an illustration of this
create table table1 (t1id int , name varchar(100));
insert into table1 values (1,'aa'),(2,'cc'),(3,'dd'),(4,'ee'),(5,'ff'),(6,'bb'),(7,'gg');
create table table2 (t2id int, description varchar(100));
insert into table2 values (1,'desc1'),(2,'desc2'),(3,'desc3');
create table table3 (t3id int, t1id int , t2id int);
insert into table3 values (1,1,2),(2,3,2),(3,2,2),(4,7,3);
create table table4 (t4id int , t1id int ,fieldid int);
insert into table4 values (1,1,10),(2,3,23),(3,4,34),(4,5,50);
select
t1.t1id,
t1.name,
t2.description,
t4.fieldid
from table1 t1
left join table3 t3 on t3.t1id = t1.t1id
left join table2 t2 on t2.t2id = t3.t2id
left join table4 t4 on t4.t1id = t1.t1id;
+------+------+-------------+---------+
| t1id | name | description | fieldid |
+------+------+-------------+---------+
| 1 | aa | desc2 | 10 |
| 2 | cc | desc2 | NULL |
| 3 | dd | desc2 | 23 |
| 4 | ee | NULL | 34 |
| 5 | ff | NULL | 50 |
| 6 | bb | NULL | NULL |
| 7 | gg | desc3 | NULL |
+------+------+-------------+---------+
The above example is similar to what you have.

Answer 2

If you still want to use INNER
1. Try a LEFT JOIN instead a INNER JOIN, and put a condition in WHERE
SELECT a.itemid as ID, a.title as Name, c.name as Categories, d.data_txt as Description, d.fieldid as FieldID FROM `jos_sobi2_item` as a
LEFT JOIN `jos_sobi2_cat_items_relations` as b ON b.itemid=a.itemid
LEFT JOIN `jos_sobi2_categories` as c ON c.catid = b.catid
LEFT JOIN `jos_sobi2_fields_data`as d ON a.itemid=d.itemid
WHERE b.itemid IS NULL OR c.catid IS NULL OR d.itemid IS NULL
Look at your results and see where you have nulls, after that you will discover what records from the jos_sobi2_item don't have a connection in the other tables.
Or if you want to use LEFT JOIN :
1.Run the query:
SELECT a.itemid as ID, a.title as Name, c.name as Categories, d.data_txt as Description, d.fieldid as FieldID,
COUNT(b.itemid), COUNT(c.catid), COUNT(d.itemid)
FROM `jos_sobi2_item` as a
LEFT JOIN `jos_sobi2_cat_items_relations` as b ON b.itemid=a.itemid
LEFT JOIN `jos_sobi2_categories` as c ON c.catid = b.catid
LEFT JOIN `jos_sobi2_fields_data`as d ON a.itemid=d.itemid
GROUP BY a.itemid
Analyze the counts for duplicate records, you can put a condition where count > 1 on every count.