Multiple table fields in an itab.

Question

Hi friends,
i have a query about a report where i have to display fields from 4 different tables in a report output by taking all those fields into a single internal table.
mara,marc,mard, makt are the tables involved.
now the only way to do this is join condition. Am i right or is there a better way of getting the required output without using joins??
any suggestion is welcome.

Answer 1

Rob,
to see which variant is better he needs to test on big enough data amount (close to production, if there is one). I think you agree that some variants which work fine on small data volumes may work bad on a really big data volumes...
I would use the simple rule to select between join vs for all entries :
- join is more DB-optimizer dependent and if wrong path is used - it's going to be a problem, from the other hand if all join conditions are defined well and WHERE is not very complex - it may work faster, besides - it returns just the data you need... so no unnecessary transfers from DB to applicaiton server. More tables you add to join -> more depends on optimizer to choose the right access path.
- for all entries less dependent on DB optimizer as usually you provide key fields in WHERE clause for corresponding table, works fast enough assuming it's written properly (check for empty intenal table before selecting, no duplicates in the internal table,...), BUT it requires more memory on application server especially when you need to select just a couple of fields but your where condition is contains fields which you don't need in your result, OR if your selection is not very restrictive on some tables which can result in big enough internal table... so if the space is an issue - I would select join.
I had to replace join with select for all entries in some cases as optimizer selected wrong path (it may be a problem with optimizer and not with join itself,,, but often we need to write code which wors fast now and not after SAP fixed error somewhere in optimizer ).