Question

I am using DB2 database.

I have a query like:

DELETE FROM MYSCHEMA.MY_TABLE WHERE (PROD LIKE 'AB%' OR PROD LIKE 'CD%' OR PROD LIKE 'EF%');

Above query is present in a properties file and I am executing it using a java program.

However, now I want to externalize the where condition.

I have created a new Table PROD_LIKE having a single column PROD_NAME with entries as below:

PROD_NAME
------------
AB
CD
EF
------------

I want to modify the delete query’s where condition such that it uses the entries present in above newly created table.

How can I achieve it ?

DB2 documentation says:

Resolving the problemEven though other databases like SQL Server or Oracle allow the use of database columns for both operands in a “like” comparison, DB2 is more restrictive. When the query database is a DB2 one has to avoid calculations or selects like the above mentioned. There is no way to use a database column as second operand when querying a DB2 and using “like” in a comparison.

What could be the alternative for this ?

Answer 1

In TSQL I’d probably do this,

DELETE 
   T
FROM 
    MYSCHEMA.MY_TABLE T 
    INNER JOIN PROD_NAME P
      ON LEFT(T.PROD,2) = P.PROD_NAME

I’m sure the DB2 SQL is similar as I’m sure this is pretty much ANSI SQL.

You could also try a more general to get rid of the hard coded 2

DELETE 
   T
FROM 
    MYSCHEMA.MY_TABLE T 
    INNER JOIN PROD_NAME P
      ON LEFT(T.PROD, LEN(P.PROD_NAM)) = P.PROD_NAME

I don’t see why you need a like but yes you can if you want.

DELETE 
   T
FROM 
    MYSCHEMA.MY_TABLE T 
    INNER JOIN PROD_NAME P
      ON T.PROD LIKE P.PROD_NAME + '%'