php small query help

PHP Code:

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$query = "SELECT * FROM `Student`"; 


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Thats fine, but i need to extend it.

The Students table has a field called 'Student_ID'
The Persons table has a field called 'Student_ID' (foreign key etc)

I want to select all the entries from the 'Student' table where the 'Student_ID' is not in the 'Persons' table

any help guys?

What db are you using? If mysql then you should search about joins I think there is equivalent about inner join in mssql to mysql.

in mssql.
$query = 'select * from student s inner join persons p where s.student_id=p.student_id';

That should also work in MySQL.