08_abap - internal tables

7/30/2019 08_ABAP - Internal Tables

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ABAP - Internal Tables


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Contents

Objectives

Internal Table Basics

Definition of an Internal Table

APPEND Statement

Reading Data from an Internal Table

Sorting the Contents of an Internal Table

Summary

Q&A


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Contents

Objectives


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Objectives

Define an internal table:

with or without a header line

using the DATA and INCLUDE STRUCTURE statements.

Fill an internal table:

using APPEND via a header line or an explicit work area.

Use LOOP AT and LOOP AT...WHERE

Use SY-TABIX to determine the current row index.

Locate a single row in an internal table: using READ TABLE.

Sort internal tables.


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Contents

Internal Table Basics


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Internal Table

internal table: a temporary table stored in RAM on theapplication server

created and filled by a program during execution

discarded when the program ends

consists of one or more rows with an identical structure

consists of a bodyand an optional header line

body: holds the rows of the internal table (itab)

all rows have the same structure header line: a field string with the same structure as a

row

the single row buffer of the itab


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Internal Table

OCCURS: to create the body of itab

no OCCURS field string

Itab with header line: use BEGIN OF orWITH HEADER LINE

A nested internal table cannot have aheader line

DATA: BEGIN OF it1 OCCURS 10, "has a header line

f1,

f2,

f3,

END OF it1.

DATA it2 LIKE lfa1 OCCURS 100. "doesn't have a header line

DATA it3 LIKE lfa1 OCCURS 100 WITH HEADER LINE. "it does now


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Internal Table

the body and the header line have the same name

Which is referred?

Where in code?

In assignment statements header line

it-f1 = A

field f1 of header line it


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Internal Table - Examples*header line

DATA: BEGIN OF it1 OCCURS 10,

f1,

f2,

f3,

END OF it1.

*no header line

DATA it2 LIKE lfa1 OCCURS 100.

*header line

DATA it3 LIKE lfa1 OCCURS 100 WITH HEADER

LINE.

*no header line

DATA it4 LIKE it3 OCCURS 100.

*header line

DATA BEGIN OF it5 OCCURS 100.

INCLUDE STRUCTURE lfa1.

DATA END OF it5.

* might use

DATA BEGIN OF it6 OCCURS 100.

INCLUDE STRUCTURE lfa1.

DATA: delflag,

rowtotal,

END OF it6.

*don't do it this way

DATA: BEGIN OF it7 OCCURS 100,s LIKE lfa1, "component names will be

END OF it7. "prefixed with it7-s-

DATA it8 LIKE sy-index OCCURS 10

WITH HEADER LINE.

DATA: BEGIN OF it9 OCCURS 10,

f1 LIKE sy-index,

END OF it9.


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APPEND Statement

to add a single row to a internal table

copy 1 row: from work area body (append to the end)

work area can be:

the header line implicit

other field string having the same structure explicit

Syntax: append [wa to] [initial line to] it.

wa is the name of a work area

itis the name of a previously defined internal table

SY-TABIX the relative row number of the rowappended

APPEND INITIAL LINE TO it appends an initial row


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APPEND Statement

DATA: BEGIN OF it OCCURS 3,

f1(1),

f2(2),

END OF it.

it-f1 = 'A'.

it-f2 = 'XX'.

APPEND it TO it.

WRITE: / 'sy-tabix =', sy-tabix.

it-f1 = 'B'.

it-f2 = 'YY'.

APPEND it.


it-f1 = 'C'.

APPEND it.



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Using the OCCURS Addition

How much memory to allocate in 1 time?

OCCURS 0 size of memory = 8KB (fixed)

OCCURS n

size of memory = min(sizeof(n lines),8KB)

Dont use OCCURS 0 if the expected itabsize


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Reading Data from an Internal Table

2 statements:

LOOP AT: to read multiple rows

READ TABLE: to read a single row


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LOOP AT Statement

Syntax: loop at it[into wa] [from m] [to n] [where exp].

---

endloop.

where: itis the name of an internal table.

wa is the name of a work area.

m and n are integer literals, constants, or variables representinga relative row number. For example, 1 means the first row in the

table, 2 means the second, and so on. exp is a logical expression restricting the rows that are read.

--- represents any number of lines of code. These lines areexecuted once for each row retrieved from the internal table.


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LOOP AT Statement

SY-TABIX:

contains the row number of the current record

1st record SY-TABIX = 1; 2nd record SY-TABIX = 2;

after ENDLOOP: SY-TABIX = the value before the

loop

SY-SUBRC:

= 0 if any rows were read

0 if no rows were read


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LOOP AT Statement - exampleREPORT y_vu_1104.

DATA: BEGIN OF it OCCURS 3,f1(1),

f2(2),

END OF it.

it-f1 = 'A'.

it-f2 = 'XX'.

APPEND it TO it. "appends header line IT to body IT

it-f1 = 'B'.

it-f2 = 'YY'.

APPEND it. "same as line 8

it-f1 = 'C'.

APPEND it. "the internal table now contains

three rows.

sy-tabix = sy-subrc = 99.LOOP AT it. "same as: loop at it into it

WRITE: / sy-tabix, it-f1, it-f2.

ENDLOOP.

WRITE: / 'done. sy-tabix =', sy-tabix,

/ ' sy-subrc =', sy-subrc.


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Using the FROM, TO, and WHERE additions

REPORT y_vu_1105.

DATA: BEGIN OF it OCCURS 3,f1(1),

f2(2),

END OF it.

it-f1 = 'A'.

it-f2 = 'XX'.

APPEND it.

it-f1 = 'B'.

it-f2 = 'YY'.APPEND it.

it-f1 = 'C'.

APPEND it.

LOOP AT it WHERE f2 = 'YY'. "f2 is right, it-f2 would be wrong here


ENDLOOP.

LOOP AT it TO 2. "same as: loop at it from 1 to 2.


ENDLOOP.

LOOP AT it FROM 2. "same as: loop at it from 2 to 3.


ENDLOOP.


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Using EXIT, CONTINUE, and CHECK

EXIT:

terminates the loop immediately

go to the statement after ENDLOOP

CONTINUE:

go to the beginning of the next pass

CHECK exp:

If exp = TRUE: do nothing

If exp = FALSE: same as CONTINUE


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READ TABLE Statement

to read a single row from an itab

Syntax:

read table it[into wa] [index i| with key keyexp.

where: itis the name of an internal table.

wa is the name of a work area.

iis an integer literal, constant, or variable representing arelative row number. For example, 1 means the first row inthe table, 2 means the second, and so on.

keyexp is an expression representing a value to be found.


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Using the INDEX Addition

index: 1st row in the table index 1; 2nd row

index 2;

READ TABLE IT INDEX i: reads the ith

row fromthe itab and places it in the header line.

If successful (the ith row exists)

SY-SUBRC = 0

SY-TABIX = i


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INDEX - example

REPORT y_vu_1106.

DATA: BEGIN OF it OCCURS 3,

f1(2) TYPE n,f2 TYPE i,

f3(2) TYPE c,

f4 TYPE p,

END OF it,

wa LIKE it.

it-f1 = '10'. it-f3 = 'AA'. it-f2 = it-f4 = 1. APPEND it.

it-f1 = '20'. it-f3 = 'BB'. it-f2 = it-f4 = 2. APPEND it.

it-f1 = '30'. it-f3 = 'CC'. it-f2 = it-f4 = 3. APPEND it.

READ TABLE it INDEX 2.

WRITE: / 'sy-subrc =', sy-subrc,

/ 'sy-tabix =', sy-tabix,

/ it-f1, it-f2, it-f3, it-f4.READ TABLE it INTO wa INDEX 1.

WRITE: /,

/ 'sy-subrc =', sy-subrc,/ 'sy-tabix =', sy-tabix,

/ it-f1, it-f2, it-f3, it-f4,

/ wa-f1, wa-f2, wa-f3, wa-f4.READ TABLE it INDEX 4.

WRITE: /,

/ 'sy-subrc =', sy-subrc,


/ it-f1, it-f2, it-f3, it-f4,/ wa-f1, wa-f2, wa-f3, wa-f4.


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Using the WITH KEY Addition

WITH KEY keyexp :

to find a row that matches the key expression

if > 1 row matches, the 1st one found (lowest index) is returned

Key Expression:

c1 = v1 c2 = v2 ...

component c1 has the value v1 AND component c2 has the value v2

(f1) = v1 (f2) = v2 ...

the value of f1: the name of the component (must be in uppercase)

if f1 is blank, the comparison is ignored

= wa

wa: a work area itab row structure

the 1st row in the itab exactly equal to the contents of wa

wa

wa: a work area or itab row structure (wa has n fields, the fields of wa match the first n

fields of itab row)

the 1st row in the itab whose first n fields match the contents of wa


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WITH KEY - example

READ TABLE it WITH KEY f1 = '30' f2 = 3.



/ it-f1, it-f2, it-f3, it-f4.

f = 'F2'. "must be in uppercase

READ TABLE it INTO w2 WITH KEY (f) = 2.WRITE: /,




/ w2-f1, w2-f2, w2-f3, w2-f4.


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WITH KEY - example

CLEAR w2.

w2-f1 = '10'. w2-f3 = 'AA'. w2-f2 = w2-f4 = 1.READ TABLE it WITH KEY= w2.

WRITE: /,



/ it-f1, it-f2, it-f3, it-f4.

w1-f1 = '20'. w1-f2 = 2.READ TABLE it INTO w2WITH KEY w1.

WRITE: /,




/ w2-f1, w2-f2, w2-f3, w2-f4.


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No Additions

default key: an imaginary key composed of allcharacter fields (types C, D, T, N, and X). Ex: DATA: BEGIN OF it OCCURS 3,

f1(2) TYPE n, part of default key

f2 TYPE i,f3(2) TYPE c, part of default key

f4 TYPE p,

END OF it.

READ TABLE with no additions finds a row that matches the default keyof the header

line.

Blanks in a default key field that column is ignored.


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Example

CLEAR it.

it(2) = ' '. it-f3 = 'BB'.

READ TABLE it.


/ 'sy-tabix =', sy-tabix,/ 'f1=', it-f1, 'f2=', it-f2, 'f3=', it-f3, 'f4=', it-f4.

CLEAR it.

it-f1 = '30'. it-f3 = 'AA'.

READ TABLE it.


/ 'sy-tabix =', sy-tabix,/ 'f1=', it-f1, 'f2=', it-f2, 'f3=', it-f3, 'f4=', it-f4.


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Sorting the Contents of an Internal

Table SORT statement:

sort by 1-n column(s)

ascending / descending

Syntax:

sort it[descending] [as text] [byf1 [ascending|descending] [as text]f2 ...].

where:

itis the name of an internal table.

f1 andf2 are components ofit.

... represents any number of field names optionally followed by ascending, descending,

and/or as text

NOTES: ASCENDING: default sort order.

If DESCENDING appears right after SORT default to all components.

If no additions sort by the default key fields (all fields of type C, N, D, and T)


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Example

SORT it BY f2.

f2

f1 f2

SORT it BY f2 f1 DESCENDING.

f2 f1

SORT it BY f2 DESCENDING f1.

SORT it DESCENDING BY f2 f1 ASCENDING.

f2 f1

SORT it.

f2


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Contents

Summary


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Summary

Itab: a collection of rows stored in RAM on the applicationserver: header line (optional): is the implicit work area for the itab

body

OCCURS clause: to allocate memory

does not limit the number of rows of an itab

LOOP AT statement: to retrieve multiple rows from an itab Each row is placed into the header line / explicit work area

FROM, TO, and WHERE: to specify the rows to be returned SY-TABIX: contains the 1-based relative row number

After ENDLOOP, SY-SUBRC will be zero if any rows wereprocessed


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Summary

Inside of a loop

EXIT: terminates the loop and continues with the statement following the ENDLOOP

CONTINUE: bypasses the remaining statements of the loop and immediately begins the

next iteration

CHECK: like CONTINUE when its logical expression is FALSE

READ TABLE statement: to locate a single row in the itab INDEX addition: locate a single row by relative row number

WITH KEY addition: locate a row by specifying a value to be found

SORT statement: sorts an itab by named components

If no components are named: sorted by default key fields (types C, N, D, T, X).


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Summary

08_abap - internal tables

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