Question { 2917 }

Major difference between SQL override and Lookup Sql override

Answer

1. SQL Override is to limit the number of incoming rows entering the mapping pipeline
Lookup Override is to limit the number of lookup rows to avoid the whole table scan by saving the lookup time & cache it uses.

2. Lookup Override uses "Order By" clause by default
SQL Override doesn't uses it & should provide in our query if we require it.

3. SQL Override can provide any kind of join by writing the query
Lookup Override provides only Non-Equi joins

4. Lookup Override gives only one record even if it finds multiple records for a single condition
SQL Override doesn’t do that.

Question { 882 }

Differentiate between mapping parameter and mapping variable?

Answer

A mapping parameter is a user definable constant that takes up a value before running a session. It can be used in SQ expressions, Expression transformation etc.


A mapping variable is also defined similar to the parameter except that the value of the variable is subjected to change. It picks up the value in the following order.

 From the Session parameter file
 As stored in the repository object in the previous run
 As defined in the initial values in the designer
 Data type Default values

Question { 854 }

What is the expected value if the column in an aggregator transform is neither a group by nor an aggregate expression?

Answer

If we do not use an input port in group-by neither in aggregate expression, the Integration Service
will return only the last row value of the column for the input rows.
For example, if we have 100 rows coming from source then aggregator will output only the last record (100th
record)