Question

Suppose that I have the following table:

ID:   STR:
01    abc
02    abcdef
03    abx
04    abxy
05    abxyz
06    abxyv

I need to use an SQL query that returns the ID column and the occurrences of the corresponding string as a prefix for string in other rows. E.g. The desired result for the table above:

ID:   OCC:
01    2
02    1
03    4
04    3
05    1
06    1

Answer 1

You could JOIN the table with itself and GROUP BY the ID to get you the result.

SELECT   t1.ID, COUNT(*)
FROM     ATable t1
         INNER JOIN ATable t2 ON t2.Str LIKE t1.Str + '%'
GROUP BY
         t1.ID

Some notes:

• You want to make sure you have an index on the Str column
• Depending on the amount of data, your DBMS might choke on the amount it has to handle. Worst case, you are asking for the SQR(#Rows) in your table.