LOOP & JOINS IN DATA SERVICES
diff. bw loops and joins.
which one is better to data service approach. why?
Raghunathan Balasubramanian replied
Joins are meant used to combine data between different sources for a specific condition and produce output that meet the join criteria. This is similar to a SQL SELECT statement that joins two tables with a WHERE segment that has conditions to match the relevant records. Joins are usually used within dataflows or in scripts.
As far as looping is concerned you repeat the same process more than once for a specific number of times as long as the condition in the loop is met with. In this case you repeat the same process that is within the loop over and over. In a loop you can call the same dataflow or script performing the join as may times as you need.
In case of full pushdown, you can achieve this in your dataflow using more than one performance optimization technique.
1. You can use the data transfer transform
2. or use the pushdown_sql function within the dataflow
3. or you can define the dataflow join condition in such a way that the optimized SQL will result in a INSERT/SELECT statement.
Hope this helps.