Question

Please help me in this….

1. There are few databases DB1,DB2,DB3,DB4,DB5….

2. each database has same tables T1,T2,T3…..Tn. (each table has same columns C1, C2, C3……Cn… but data in those tables are different)

3. Requirement: *query:* select C1, C2, C3 from T1 inner join T2 on T1.C4 = T2.C4

   the query will be same for all databases.

4. First step is to create drop down menu for Databases DB1, DB2, DB3, DB4, DB5

5. Then select one or more databases after that the query should run for selected database or databeses.

What source should I select and how to create dataset for them?

Answer 1

Create a parameter called something like SelectedDatabase.

Hard-code the values of the available databases within it.

Change the query expression to be something like:

="select C1, C2, C3 from " & Parameters!SelectedDatabase.Value & ".T1 inner join " & Parameters!SelectedDatabase.Value & ".T2 on T1.C4 = T2.C4"

This is an example of a dynamic query – you can find out more here.

Note that if users can directly enter values that will be used in a dynamic query, you will be opening your code to the risk of SQL injection attacks (obligatory XKCD reference here). This is why you should hard-code the available values (if possible).