Question

We have a table like,

Table1(Contract_id, name, address, contact_no)

and another table like,

Table2(Contract_id, approver, owner, authority)

Sample data:

mysql> select * from Table1;
+-------------+-------+---------+------------+
| contract_id | owner | address | contact_no |
+-------------+-------+---------+------------+
|       11111 | XXX   | Madurai | 897161     |
|       12456 | XYZ   | Madras  | 897161     |
|       11111 | XYZ   | Madras  | 897161     |
+-------------+-------+---------+------------+
3 rows in set (0.00 sec)

mysql> select * from Table2;
+-------------+----------+
| contract_id | approver |
+-------------+----------+
|       11111 | YZX      |
|       11112 | YYY      |
+-------------+----------+
2 rows in set (0.00 sec)

I have written a query to get all contract_ids and matching data for a criteria like this,

“Get all contracts with Owner like ‘X’ and address like “Mad” and approver = ‘YZX'”

select contract_id,owner,address,approver 
from 
(
    select *
    from Table1 
    where owner like '%X%' 
    and address like '%Mad%'
) t1 
inner join 
(
    select * 
    from Table2 
    where approver = 'YZX'
) t2 using (contract_id);

It is returning the results correctly. But the problem is left table has two matching rows and right table has only one matching row. So the row in right table is duplicated twice.

> +-------------+---------------+-----------+-------------+
> |contract_id  |  owner        | address   | approver    |
> +-------------+---------------+-----------+-------------+
> |11111        | XXX           | Madurai   | YZX         |
> +-------------+---------------+-----------+-------------+
> |11111        | XYZ           | Madras    | YZX         | 
> +-------------+---------------+-----------+-------------+

The approver value is duplicated twice. Can i somehow avoid this mysql itself?
I want null value for the second row’s approver column.

EDIT 1:

I edited my query to have group by approver at the end,

select contract_id,owner,address,approver 
from 
(
    select contract_id
    from Table1 
    where owner like '%X%' 
    and address like '%Mad%'
) t1 
inner join 
(
    select contract_id 
    from Table2 
    where approver = 'YZX'
) t2 using (contract_id) group by approver;

Now the results became like,

> +-------------+---------------+-----------+-------------+
> |contract_id  |  owner        | address   | approver    |
> +-------------+---------------+-----------+-------------+
> |11111        | XYZ           | Madurai   | YZX         |
> +-------------+---------------+-----------+-------------+

The second went missing now. I want that as well.

EDIT 2: Added the sample data and exact queries.

EDIT 3: I want the results to be formatted like the below,

> +-------------+---------------+-----------+-------------+
> |contract_id  |  owner        | address   | approver    |
> +-------------+---------------+-----------+-------------+
> |11111        | XXX           | Madurai   | YZX         |
> +-------------+---------------+-----------+-------------+
> |11111        | XYZ           | Madras    | NULL        | 
> +-------------+---------------+-----------+-------------+

EDIT 4: I acheived what I wanted. Below is the query I used.

create temporary table table1 select * 
from 
(
    select *
    from Table1 
    where owner like '%X%' 
    and address like '%Mad%'
) t1 
inner join 
(
    select * 
    from Table2 
    where approver = 'YZX'
) t2 using (contract_id) limit 1;

and the query,

insert into table1 select contract_id, IF((select count(*) from table1 where owner = t.owner and contract_id = t.contract_id) > 0, NULL, t.contract_id),IF((select count(*) from table1 where address = t.adress and contract_id = t.contract_id) > 0, NULL, t.contract_id),IF((select count(*) from table1 where approver = t.approver and contract_id = t.contract_id) > 0, NULL, t.contract_id)
from 
((
    select *
    from Table1 
    where owner like '%X%' 
    and address like '%Mad%'
) t1 
inner join 
(
    select * 
    from Table2 
    where approver = 'YZX'
) t2 using (contract_id)) t;  

Answer 1

Just to be clear the data is not duplicating. Since you are joining the two tables on contract_id and the same contract id is associated with two records, you will have the approver appear twice.

mysql> select * from Table1;
+-------------+-------+---------+------------+
| contract_id | owner | address | contact_no |
+-------------+-------+---------+------------+
|       11111 | XXX   | Madurai | 897161     | -- contract_id 11111
|       12456 | XYZ   | Madras  | 897161     |
|       11111 | XYZ   | Madras  | 897161     | -- contract_id 11111
+-------------+-------+---------+------------+
3 rows in set (0.00 sec)

mysql> select * from Table2;
+-------------+----------+
| contract_id | approver |
+-------------+----------+
|       11111 | YZX      | -- contract_id 11111
|       11112 | YYY      |
+-------------+----------+
2 rows in set (0.00 sec)

So the result will always be two records from table1 and one record from table two with an approver = 'YZX'

On another note, I might consider rewriting the query to the following:

select t1.contract_id, t1.owner, t1.address, t2.approver 
from table1 t1
inner join table2 t2
  on t1.contract_id = t2.contract_id
where t1.owner like '%X%'
  and t1.address like '%Mad%'
  and t2.approver = 'YZX'

Based on your comment, I am beginning to think you might want a LEFT JOIN:

select t1.contract_id, t1.owner, t1.address, t2.approver 
from table1 t1
left join table2 t2
  on t1.contract_id = t2.contract_id
  and t2.approver = 'YZX'
where t1.owner like '%X%'
  and t1.address like '%Mad%'

See SQL Fiddle with Demo

Edit 2: There is not simple way to force this to use a null for additional fields. You can attempt to use a rownumber to get the results:

select x.contract_id, 
  x.owner,
  x.address,
  case when (@rownum:=@rownum+1 = 1) then x.approver else null end approver
from 
(
  select t1.contract_id, t1.owner, t1.address, t2.approver
  from table1 t1
  inner join table2 t2
    on t1.contract_id = t2.contract_id
    and t2.approver = 'YZX'
  where t1.owner like '%X%'
    and t1.address like '%Mad%'
) x, (SELECT @rownum:=0) r

See SQL Fiddle with Demo