与使用php的mysql嵌套选择查询混淆

Question

please help to find what the mistake here. Actually i am a beginner.. Help Me..

$query1="select Sub_Code,Sub_Name from subj_mast where Dept_id='(select Dep_Id from academic where Reg_No=$reg)' and Sem='$sem'";

The above query is not working but when i split like this its working...

$query2="select Dep_Id from academic where Reg_No=$reg";
$query3="select Sub_Code,Sub_Name from subj_mast where Dept_id='104' and Sem='$sem'";

here 104 is Dept_id corresponds to Reg_No given. 104 is got by using query2. Confused a lot ... is my query1 is right???

Answer 1

You're wrapping your subquery inside of quotes. Remove the quotes.

Eg:

$query1="select Sub_Code,Sub_Name from subj_mast where Dept_id=(select Dep_Id from academic where Reg_No=$reg) and Sem='$sem'";