RE: Knotty puzzle with chaining to files not known at compile time

["Larry Ducie" <larry_ducie@xxxxxxxxxxx>]

Hi Carel,

<snip>
The QSQPRCED API uses the SQLDA descriptor. The SQLDA data structure 
contains an array, which you have to lopp through to get the column data 
retrieved.

You can also use embedded SQL with descriptor SQLDA, which makes that form 
of SQL dynamic.

It seems James, the originator, cannot use embedded SQL.
</snip>

Absolutely! Both methods use the SQLDA, but using the QSQPRCED API isn't the 
same as using dynamic embedded SQL:

When you use embedded SQL you create a SQL ILE RPG Object (CRTSQLRPGI). This 
object contains the information about communicating with the database - such 
as the SQL package to be used, RDB connect method, cursor behaviour, SQL 
rules, etc... To compile this object I believe you need the DB2 Query Mgr 
and SQL DevKit (5722ST1 on V5R4M0) installed. You simply place the SQL 
directives in your program and the SQL pre-compiler creates the appropriate 
structures for you. You don't even need to know that the SQLDA exists.

When you use the QSQPRCED API you can create a bound RPG program 
(CRTBNDRPG). The calls via QSQPRCED externalise the interaction with the 
database so you don't need any special development tools to compile your 
program object. Like many system APIs - you get it for free, but it just 
takes a little more work to use it. It is your responsibility to create the 
SQL package, prepare the statement into the package, describe the result set 
into the SQLDA, set the parameter markers, open the cursor, fetch the 
results, and close the cursor. This is mostly achieved through calls to 
QSQPRCED and is pretty straightforward, if a little confusing at first 
sight.

So, anybody can run dynamic SQL statements from within their RPG programs - 
you don't need to use embedded SQL.

Cheers

Larry Ducie