Purpose of using wild cards in SAP-ABAP

Question

what is the purpose of using the following in ABAP programs.
In my case these naming convention are used in Reports * (Custom Programs)
1> tables: *nast.
why we use * before the table name?
2> Data:  %var1 type mara-matnr,
What for this % is used to declare the variable. what effect it will have?
              %%var1 type marc-werks.
this kind of declaration is also used, what purpose?
3> Perform %<form-name>.
A sub routine is called with the above kind of syntax, what purpose?
Please help me to find what purpose they are used?
Message was edited by:
        VK AJAY
Message was edited by:
        VK AJAY

Answer 1

HI,
WILDCARD characters which are used for comparisions with character strings & numeric strings.
Refer samplecode:
Example to select all customers whose name begins with 'M':
DATA SCUSTOM_WA TYPE SCUSTOM.
SELECT ID NAME FROM SCUSTOM
       INTO CORRESPONDING FIELDS OF SCUSTOM_WA
       WHERE NAME LIKE 'M%'.
  WRITE: / SCUSTOM_WA-ID, SCUSTOM_WA-NAME.
ENDSELECT.
Example to select all customers whose name contains 'huber':
DATA SCUSTOM_WA TYPE SCUSTOM.
SELECT ID NAME FROM SCUSTOM
       INTO CORRESPONDING FIELDS OF SCUSTOM_WA
       WHERE NAME LIKE '%huber%'.
  WRITE: / SCUSTOM_WA-ID, SCUSTOM_WA-NAME.
ENDSELECT.
Example to select all customers whose name does not contain 'n' as the second character:
DATA SCUSTOM_WA TYPE SCUSTOM.
SELECT ID NAME FROM SCUSTOM
       INTO CORRESPONDING FIELDS OF SCUSTOM_WA
       WHERE NAME NOT LIKE '_n%'.
  WRITE: / SCUSTOM_WA-ID, SCUSTOM_WA-NAME.
ENDSELECT.
Reward points if this Helps.
Manish