根据另一个表的列值从表中选择记录

Question

I know forming this query is trivial, but I am not able frame the exact query. Based on what I have read so far, the solution may include joining two tables. Here is the problem :

TABLE_ONE {S_NO, DK_NO, FRM , DATE}

TABLE_TWO {S_NO, DK_NO , TO}

I want to select a record from TABLE_ONE based on an input value of DK_NO and value checked for TO field of TABLE_TWO or FRM field of TABLE_ONE

unsuccessful trials so far:

1)

$sql = "select * from TABLE_ONE where DK_NO like '%".$dkno."%' and (FRM='".$department."' or  (TABLE_TWO.DK_NO like '%".$dakno."%' and TABLE_TWO.TO='".$department."'))";

2)

$sql = "select * from TABLE_ONE where DK_NO like '%".$dkno."%' and (FRM='".$department."' or   TABLE_TWO.TO='".$department."')";

Answer 1

Recommended reading: JOIN.

Using inner join:

"select t1.* 
from table_one t1 inner join table_two t2 on t1.dk_no = t2.dk_no
where (t1.frm = '". $department. "' or t2.to = '".$department. "') 
    and t1.dk_no like '%" . $dkno . "%'";