Comparing Strings in sql -

i have data in following format in table in column , column b.

column             column b 12345678xy           1111111 12345678xyabcn00001  1111111 

using sql, need make sure, whenever in 2 rows in column in above mentioned format, column b should have same number each of them.

could kindly me comparing strings under column a. not sure, how approach this!!!

here query may help:

select * table1 t1 inner join table1 t2 on  left(t1.column_a,10) = left(t2.column_a,10) t1.column_b <> t2.column_b 

you can see running here: http://sqlfiddle.com/#!6/129b1/1