PLSQL and substr problem

From: M.Jord <mjjugs_at_gofree.indigo.ie>
Date: Mon, 23 Aug 1999 18:32:43 +0100
Message-ID: <eNfw3.3884$r4.2249@news.indigo.ie>

I am trying to select the first seven char of a 8 characters column within a large
table.
& then compare this with existing seven digit numbers. If there is a match then I need to delete the seven digit numbers.

I have used a loop and substr(col.name,1,7) to select the digits into a cursor, and tried to compare this to a 2nd cursor which contains the 8 digits.
Can anyone help me write the pl/sql script to do this task.
eg

Table X

Herd no
A1093459
A109345 >for deletion
B2062768
B206276 >for deletion Received on Mon Aug 23 1999 - 12:32:43 CDT