informatica use summary (1)

1. Use of filter conditions The
Filter component is executed by the powercenter server, and the source filter defined in the source qualifier is actually converted into SQL statements and executed by the database server. If you want to have the least impact on data performance, it is recommended to use the filter component, but the database will have greater I/O. If you use the source filter in the source qualifier, the pressure on Powercenter is less, and if there is an index on this field on the database The effect will be better.
2. Error-prone point
1) My sql writing in sql query is:
Select a.col1,a.col2 from a ,b where a.id=b.aid,
do I need to drag both a and b tables in this case In fact, it is not necessary to enter the mapping, but it is recommended to drag these two tables into the mapping, which is to improve the readability of the program.
2) Self-join mapping
In the two branches from source qualifier to joiner, at least one branch must add another component between source qualifier and joiner;
Joinerkey must be sorted;
Joiner must Use sorted input;
3. It is best to sort before using the joiner, which can improve the performance of the joiner in most cases.
If the sorted joiner is used, the sorter component sorts the associated fields in the joiner component, and requires that the data entered into the joiner component from the master table and the detail table are in order.
Another way to get sorted data is to use the custom SQL statement order by in the source qualifier to sort the desired columns.
4. The target table structure can be dragged from the source to the target designer workspace to generate the target, but it cannot be dragged from the target to the source designer to generate a new source definition.