Re: Should I be using SQL?

[Scott Klement <midrange-l@xxxxxxxxxxxxxxxx>]

In this exammple, "MyLib" and "MyFile" are the names of RPG variables. 
This is what the SQL statement will load the results into... these RPG 
variable names.

"System_Table_Schema" is (believe it or not) the actual field name in 
the physical file that Rob is reading.  SQL can have up to 30 characters 
in the name of a field in a file.

For some reason, Rob is renaming "System_Table_Schema" as "Library" in 
his SQL statement.  That means that the result of the SELECT statement 
goes into a "Result Set" (you might think of this as a temporary file, 
except that it's in memory, not on disk -- and it contains the results 
of the query -- just a holding place within SQL for the output of the 
SELECT statement).      So in the temporary output from SQL, the field 
will be renamed from System_Table_Schema to Library.  Then this Library 
field is loaded into the MyLib variable in the RPG program.

I have no clue why Rob renamed the field before loading it into a 
variable in this particular example.

However, if you ran this statement interactively (instead of inside an 
RPG program) the column heading would read "Library" instead of 
"System_Table_Schema" which might be easier for an i5/OS veteran to 
understand.  (Since "Schema" is what libraries are called in SQL verbiage).


David Turnidge wrote:
> Thank you for this... I'm trying to learn SQL and have a question...
>
> You define "MyLib" and "MyFile", however you declare C1 selecting
> "System_Table_Schema" as "library", and System_Table_Name" as "file", from
> qsys2/systables....
>
> Then you open C1. The you Fetch C1 int :MyLib, :MyFile. What is the
> relationship between MyLib and System_Table_Schema???
>
> Thank you,
>
> Dave