Difference between collect and move stmts

Question

hi
anyone plz explain...
1. Difference between collect and move stmts
2. Badi and user exit.
gowri

Answer 1

Hi,
1.COLLECT:COLLECT is used to create unique or compressed datsets. The key fields are the default key fields of the internal table itab .
If you use only COLLECT to fill an internal table, COLLECT makes sure that the internal table does not contain two entries with the same default key fields.
If, besides its default key fields, the internal table contains number fields,the contents of these number fields are added together if the internal table already contains an entry with the same key fields.
If the default key of an internal table processed with COLLECT is blank, all the values are added up in the first table line.
If you specify wa INTO , the entry to be processed is taken from the explicitly specified work area wa . If not, it comes from the header line of the internal table itab .
After COLLECT , the system field SY-TABIX contains the index of the - existing or new - table entry with default key fields which match those of the entry to be processed.
COLLECT can create unique or compressed datasets and should be used precisely for this purpose. If uniqueness or compression are unimportant, or two values with identical default key field values could not possibly occur in your particular task, you should use APPEND instead. However, for a unique or compressed dataset which is also efficient, COLLECT is the statement to use.
If you process a table with COLLECT , you should also use COLLECT to fill it. Only by doing this can you guarantee that the internal table will actually be unique or compressed, as described above and COLLECT will run very efficiently.
If you use COLLECT with an explicitly specified work area, it must be compatible with the line type of the internal table.
In 'move' the actually data copies into another data field
2.
Difference between BADI and USER-EXIT.
i) BADI's can be used any number of times, where as USER-EXITS can be used only one time.
Ex:- if your assigning a USER-EXIT to a project in (CMOD), then you can not assign the same to other project.
ii) BADI's are oops based.
A. BAdI Definition
1. SE18
2. Enter the name for the BAdI to be created in customer namespace and press "Create".
3. Enter a definition for your BAdI and on the interface tab enter a name for the BAdI interface. SAP proposes a name and it is pretty good. Meanwhile a BAdI class is also created which is not in our concern.
e.g for "ZTEST", SAP proposes "ZIF_EX_TEST" for the interface and "ZCL_EX_TEST" for the class.
4. Save your BAdI.
5. Double-click on the interface name. It will pass to a Class Builder session to make you implement your interface. If you are not familiar to the Class Builder; it's a bit like Function Builder and it will be easy to discover its procedure.
6. Save and activate your interface.
B. Calling your BAdI from an application program
1. Declare a reference variable with reference to the Business Add-In interface.
e.g. DATA exit_ref TYPE REF TO zif_ex_test.
2. Call the static method GET_INSTANCE of the service class CL_EXITHANDLER. This returns an instance of the required object.
e.g.
CALL METHOD CL_EXITHANDLER=>GET_INSTANCE
CHANGING instance = exit_ref .
3. After those two steps, you can now call all of the methods of the BAdI where it is required in your program. Make sure you specify the method interfaces correctly.
C. BAdI Implementations
1. SE19
2. Enter the name for the BAdI implementation to be created in customer namespace and press "Create".
3. It will request the BAdI definition name to which this implementation will be tied.
4. Enter a definition for your implementation and on the interface tab enter a name for the implementing class. Again SAP proposes a name and it is pretty good.
e.g for "ZIMPTEST", SAP proposes "ZCL_IM_IMPTEST".
5. Save your implementation.
6. To implement a method, just double-click on the method name and you will be taken to the Class Builder to write the code for it. Here you redefine the BAdI interface methods.
7. You must activate your implementation to make it executable. You can only activate or deactivate an implementation in its original system without modification. The activation or deactivation must be transported into subsequent systems
Regards