Wht does it mean - "ASSIGN it_DB_TBL_name TO fs1 CASTING TYPE x"?

Question

Hi Experts,
Just curious,
Pls. let me know that, Wht is the functionality of the following statement:
ASSIGN it_DB_TBL_name TO <fs1> CASTING TYPE x
thanq

Answer 1

ASSIGN feld TO <fs> CASTING TYPE type.
ASSIGN feld TO <fs> CASTING TYPE (typename).
ASSIGN feld TO <fs> CASTING LIKE fld.
ASSIGN feld TO <fs> CASTING DECIMALS dec.
You can use ASSIGN ... CASTING to treat the contents of a field as a value of another type using a field symbol. One application for this statement would be to provide different views on a structure with casts on different types.
One wide-spread ABAP technique is to use C fields or structures as containers for storing structures of different types that are frequently only known at runtime. The components of the structure are selected with offset/length accesses to the container. Since this technique no longer works with Unicode, you can also look upon an existing memory area as a container with the suitable type definition using a field symbol with the ASSIGN ... CASTING statement. In the next example, a certain field of database table X031L is read, whereby the field and table names are only defined at runtime.
Example:
* Read a field of table X031L
PARAMETERS:
  TAB_NAME    LIKE SY-TNAME,             "Table name
  TAB_COMP    LIKE X031L-FIELDNAME,      "Field name
  ANZAHL      TYPE I DEFAULT 10.         "Number of lines
DATA:
  BEGIN OF BUFFER,
    ALIGNMENT TYPE F,                    "Alignment
    C(8000)   TYPE C,                    "Table contents
  END OF BUFFER.
FIELD-SYMBOLS:
  <WA>   TYPE ANY,
   TYPE ANY.
* Set field symbol with suitable to buffer area
ASSIGN BUFFER TO <WA> CASTING TYPE (TAB_NAME).
SELECT * FROM (TAB_NAME) INTO <WA>.
  CHECK SY-DBCNT < ANZAHL.
  ASSIGN COMPONENT TAB_COMP OF STRUCTURE <WA> TO .
  WRITE: / TAB_COMP, .
ENDSELECT.
Until now, in the ASSIGN feld TO <f> CASTING ... statement, the system checked to ensure that the field was at least as long as the type that was assigned to the field symbol, <f>. (Field symbols can either be typed at declaration or the type specified in an ASSIGN statement using CASTING TYPE). The syntax check is now more thorough. Now, you can only assign the field field (in either a Unicode or non-Unicode program)
provided it is at least as long as the type assigned to the field symbol <f>. Otherwise, the system returns a syntax error. At runtime, the system only checks to see whether or not the lengths are compatible in the current system (as before).
If the field type or field symbol type is a deep structure, the system also checks that the offset and type of all the reference components match in the area of field that is covered by <f>. The syntax check is now more thorough. Now, the system checks that these components must be compatible with all systems, whether they have a one-byte, double-byte, or four-byte character length. At runtime, the system only checks to see whether or not the reference components are compatible in the current system
In Unicode systems, in the ASSIGN str TO <f> TYPE C/N and ASSIGN str TO <f> CASTING TYPE C/N statements, the length of str may not always be a multiple of the character length, in which case the program terminates at runtime.