DESCRIBE TABLE is the statement to get the attributes like the number of lines, the line width of each row, etc. of the internal table. DESCRIBE TABLE statement also fills the system fields SY-TFILL (Current no. of lines in internal table), SY-TLENG (line width of the internal table), etc.

DESCRIBE TABLE <internal table> [LINES <lines>].

SORT is the statement to sort an ABAP internal table. We can specify the direction of the sort using the additions ASCENDING and DESCENDING. The default is ascending.

SORT <internal table> [ASCENDING|DESCENDING]

We can also delete the adjacent duplicates from an internal table by using the following statement.

DELETE ADJACENT DUPLICATE ENTRIES FROM <internal table> 
                 [COMPARING <f1> <f2> ... |ALL FIELDS].

COMPARING ALL FIELDS is the default. If we do not specify the COMPARING addition, then the system compares all the fields of both lines. If we specify fields in the COMPARING clause, then the system compares only the fields specified after the COMPARING of both the lines. If at least one line is deleted, the system sets SY-SUBRC to 0, otherwise to 4.

*--------------------------------------------------------------*
*Data Types
*--------------------------------------------------------------*
TYPES: BEGIN OF ty_student,
       id(5)     TYPE n,
       name(10)  TYPE c,
       place(10) TYPE c,
       age       TYPE i,
       END OF ty_student.

*--------------------------------------------------------------*
*Data Declaration
*--------------------------------------------------------------*
DATA: gwa_student TYPE ty_student.
DATA: it  TYPE TABLE OF ty_student.
DATA: gv_lines TYPE i.

gwa_student-id     = 1.
gwa_student-name   = 'JOHN'.
gwa_student-place  = 'London'.
gwa_student-age    = 20.
APPEND gwa_student TO it.

gwa_student-id     = 2.
gwa_student-name   = 'JIM'.
gwa_student-place  = 'New York'.
gwa_student-age    = 21.
APPEND gwa_student TO it.

gwa_student-id     = 3.
gwa_student-name   = 'JACK'.
gwa_student-place  = 'Bangalore'.
gwa_student-age    = 20.
APPEND gwa_student TO it.

gwa_student-id     = 4.
gwa_student-name   = 'ROB'.
gwa_student-place  = 'Bangalore'.
gwa_student-age    = 22.
APPEND gwa_student TO it.

gwa_student-id     = 2.
gwa_student-name   = 'JIM'.
gwa_student-place  = 'New York'.
gwa_student-age    = 21.
APPEND gwa_student TO it.

DESCRIBE TABLE it LINES gv_lines.
WRITE:/ 'No. of lines in IT : ', gv_lines.

WRITE:/ 'SY-TFILL : ', sy-tfill.
WRITE:/ 'SY-TLENG : ', sy-tleng.

WRITE:/ 'Values in IT before SORT' COLOR 4.

WRITE:/ 'ID' COLOR 5,7 'Name' COLOR 5, 18 'Place' COLOR 5,
        37 'Age' COLOR 5.
LOOP AT it INTO gwa_student.
  WRITE:/ gwa_student-id, gwa_student-name, gwa_student-place,
          gwa_student-age.
ENDLOOP.

WRITE:/ 'Values in IT after SORT' COLOR 4.

*SORT by name
SORT it BY name DESCENDING.

WRITE:/ 'ID' COLOR 5,7 'Name' COLOR 5, 18 'Place' COLOR 5,
        37 'Age' COLOR 5.
LOOP AT it INTO gwa_student.
  WRITE:/ gwa_student-id, gwa_student-name, gwa_student-place,
          gwa_student-age.
ENDLOOP.

WRITE:/ 'Values in IT after deleting duplicates' COLOR 4.

*Delete duplicates
SORT it.
DELETE ADJACENT DUPLICATES FROM it.

WRITE:/ 'ID' COLOR 5,7 'Name' COLOR 5, 18 'Place' COLOR 5,
        37 'Age' COLOR 5.
LOOP AT it INTO gwa_student.
  WRITE:/ gwa_student-id, gwa_student-name, gwa_student-place,
          gwa_student-age.
ENDLOOP.

WRITE:/ 'Values in IT after deleting duplicates comparing place' COLOR 4.

*Delete duplicates comparing only place
SORT it BY place.
DELETE ADJACENT DUPLICATES FROM it COMPARING place.

WRITE:/ 'ID' COLOR 5,7 'Name' COLOR 5, 18 'Place' COLOR 5,
        37 'Age' COLOR 5.
LOOP AT it INTO gwa_student.
  WRITE:/ gwa_student-id, gwa_student-name, gwa_student-place,
          gwa_student-age.
ENDLOOP.

Output