Internal Tables

*   It is  temporary  memory  location , which is used to store the data of database.

*   Internal table can store multiple records . i.e; 8KB size is allocated for internal   tables.

*   By default we cannot do any operation on internal tables.

*   If we want to do any operation on internal tables ,then we have to create a separate    memory called as  " WORK AREA".

WORK AERA:

It is also a temporary memory location , which can store a single record in the memory.

We can do any operation on the work areas.

Once the operation is finished on work area, then we modify the internal Tables.

Syntax for  Internal  tables:

DATA<ITABNAME> TYPE  TABLE  OF  <DB TABLE NAME> DATA<ITABNAME>  TYPE  TABLE  OF  <USER-DEFINED TABLE> DATA<ITABNAME>  TYPE  TABLE  OF  <DB.TABLE> OCCURS 0 WITH         HEADER   LINE.

Syntax for  Work Area:

DATA <WA_NAME>  TYPE  <DB.TABLE> DATA <WA_NAME>  TYPE  <USER-DEFINED TYPE>

Relation  B/W ITAB & WA:

SELECT:

It is  a  keyword, which is used  to select  the data from DataBase  table into Internal Table (or)WorkArea.

Syntax:

SELECT   *  (or) F1  F2  F3 - - - -                       From <DB.Table>                       Into   <ITab/ WA>                       Where   F1  = <Value>                       And       F2  = <Value>                                       .                                       .

LOOP.........ENDLOOP:

It  is a Keyword, which is used to  LOOP  (or)  read each record from Internal Table to  Work Area.

Syntax:

LOOP AT <ITAB>  INTO <WA>   ---   ---   --- ENDLOOP.

Ex  1:

Report  ZEX_PRG.

* Data Declarations

DATA:  I_ZCUST_TABLE  TYPE  TABLE  OF  ZCUST_TABLE.

DATA:  WA_ZCUST_TABLE  TYPE  ZCUST_TABLE.

Select  *  from  ZCUST_TABLE  into Table  I_ZCUST_TABLE.

Loop At  I_ZCUST_TABLE  into  WA_ZCUST_TABLE.

      Write : /  WA_ZCUST_TABLE-- CUSTNO,

                      WA_ZCUST_TABLE-- CNAME,

                        WA_ZCUST_TABLE-- CITY,

                        WA_ZCUST_TABLE-- GENDER.

 Endloop.

Ex  2:

Report   ZKNA1_PRG.

DATA : I_KNA1  TYPE  TABLE OF   KNA1.

DATA : WA_KNA1  TYPE  KNA1.

Select  *  from  KNA1  into  I_KNA1.

Loop at  I_KNA1  into WA_KNA1.

    write : /  WA_KNA1-- KUNNR,

                    WA_KNA1-- NAME1,

                    WA_KNA1-- LAND1,

                     WA_KNA1-- ORT01.

Endloop.

USER-DEFINED TYPE:

Types  is a keyword, which is used to defined User-defined fields for internal table (or) WorkArea instead of all the fields from  "DataBase Tables".

Syntax:

Types : Begin Of <TypeName>,                F1 (Length)  Type  <DataType>,                F2                   Type  <TableName-Fname>,                F3                   Type  <TableName--Fname>,                 .                                        .                 .                                        .               Endof  <TypeName>.

Ex 1:

Report  ZType-Table.

Type: Begin of  TY_MARA,

            MATNR(18)  type  MARA--MATNR,

            MTART          type  MARA--MTART,

            MBRSH          type  MARA--MTART,

            End of TY_MARA.

DATA : I_TY_MARA  type table of  TY_MARA.

DATA : WA_TY_MARA  type TY_MARA.

Select  MATNR  MTART  MBRSH  from MARA into  table I_TY_MARA.

LOOP AT  I_TY_MARA  into  WA_TY_MARA.

    write :/  WA_TY_MARA--MATNR,

                   WA_TY_MARA--MTART,

                   WA_TY_MARA--MBRSH.   

 ENDLOOP.

SELECT  INTO  CORRESPONDING  FIELDS:

This  statement  is used whenever  the no. of  selected  fields and  internal  table  fields  are mismatched  (or) different .

In such cases , this  statement will put the  selected field  into  corresponding (or) Respective internal Table field.

Syntax:

Select    F1                F2                F3                 .                 .                From <DB.Table>                Into corresponding fields of table <ITAB>.

Ex:

The Programme is same as above with a change  in select statement.

"Select  MATNR  MTART  MBRSH  MEINS  from MARA  into  I_TY_MARA".

The above  statement  through Run-Time error, bcoz the selected fields are four,

the internal table contains only 3 fields, bcoz of this mismatch it throughs Runtime error.

Change the Stmt as below.

" Select MATNR  MTART  MBRSH  MEINS  from  MARA  into corresponding fields of table I_TY_MARA."

Note:

*   Select  into  corresponding fields should never be used in the Real-Time . Bcoz it puts extra burden on the  select stmt to compare Source  and Target Fields.

Operations on  Internal  Tables:

We  have  16 different operations. They  are,

1. APPEND.

2. INSERT.

3. SORT.

4. DESCRIBE TABLE.

5. READ TABLE--------- 1. WITH INDEX

                                           2. WITH KEY

6. LOOP...........ENDLOOP.

7. MODIFY.

8. DELETE.

9. DELETE ADJACENT DUPLICATES.

10. CLEAR.

11. REFRESH.

12. FREE.

13. APPEND  LINES OF

14. INSERT  LINES OF

15. MOVE ITAB1 TO  ITAB2.

16. COLLECT.

1. APPEND:

It is used to add  a single record  from WORKAREA  to INTERNAL TABLE.

The record is always added at bottom.

Syntax:

APPEND  <WA>  TO  <ITAB>.

2.INSERT:

It is used to insert a record from  WA  into  ITAB  at a specified location.

Syntax:

INSERT <WA>  INTO <ITAB> INDEX <INDEX NO>

3.SORT:

It is used to sort the data of  internal Table in  Ascending  (or) Descending Order.

By default it is Ascending  Order.

Syntax:

SORT  <ITAB>  BY  F1  F2  F3 ............. <ASCENDING/DESCENDING>.

4.DESCRIBE TABLE:

It is  used  to find the total no. of  records in an internal table.

Syntax:

DESCRIBE TABLE  <ITAB1>  LINES <VARIABLE>.

5. i. READ TABLE  WITH INDEX:

It is used to read  a single record from ITAB  into  WA  specified by  index no.

Syntax:

READ TABLE <ITAB>  INTO <WA> INDEX <INDEX NO>.

 ii. READ TABLE  WITH  KEY:

It is also used to read a single record from  ITAB  into WA specified by field name and  field value.

Syntax:

READ TABLE <ITAB>  INTO <WA> WITH KEY  F1 name = <FVal>                                                                                             F2name = <FVal>                                                                                             F3name = <FVal>                                                                                                  .                  .                                                                                                  .                  .                                                                                             Binary search.

NOTE:

The prerequisite for binary search is, the ITAB should be sorted based on Search criteria (or) Searching fields.

6.MODIFY:

This  statement is used to modify single  (or) multiple records based on condition.

Syntax:

MODIFY<ITAB> FROM <WA> INDEX <INDEX NO>         TRANSPORTING  F1 , F2 , F3 ........

MODIFY<ITAB> FROM <WA> TRANSPORTING  F1 , F2 , F3..........                                                             WHERE   F1  =  VALUE                                                             AND         F2 =  VALUE                                                                                  .                                                                                  .

SY-TABIX:

It is a system variable which  stores the index no of   ITAB   record which is currently processed in the  WA.

TRANSPORTING:

It is a keyword which specifies the no of fields are modified from work area  to ITAB  instead of all the fields.

7.DELETE:

This statement is used to  DELETE  single (or) multiple records based on condition.

Syntax:

DELETE <ITAB> INDEX <INDEX NO>.

DELETE <ITAB> WHERE  F1  =  FVal                                  AND       F2  =  Fval                                  AND       F3  =  Fval                                                    .           .                                                    .           .

8.DELETE  ADJACENT DUPLICATES:

This statement is used to delete adjacent records from the   ITAB.

Syntax:

DELETE ADJACENT DUPLICATES  FROM <ITAB>                                         COMPARING  F1  F2  F3  ALL  FIELDS.

9.CLEAR:

This  statement is used to DELETE  the data from WA.

Syntax:

CLEAR <WA>.

10.REFRESH:

This statement is used to DELETE the data from ITAB.

Syntax:

REFRESH <ITAB>.

11.FREE:

This  statement is used to DELETE the data from  WA and ITAB.

Syntax:

FREE <WA/ITAB>.

NOTE:

Diff  b/w CLEAR , REFRESH  and  FREE  is,

CLEAR , REFRESH  will delete the data but not memory where as the FREE  statement will delete the data as well as memory also.

12.APPEND LINES OF:

This statement is used to append the data from one  ITAB into another ITAB based on the selection.

The data will append at Bottom in the 2nd ITAB.

Syntax:

APPENDLINES OF <ITAB1> FROM <INDEX NO1>                                                             TO <INDEX NO2>                                                        INTO <ITAB2>.

13.INSERT LINES OF:

This statement is used to insert the data from one ITAB to another ITAB at specified location based on the selection.

Syntax:

INSERTLINES OF <ITAB1> FROM <INDEX NO1>                                                           TO  <INDEX  NO2>                                                       INTO <ITAB2> INDEX <INDEX NO>.

14. MOVE  ITAB1[ ] TO ITAB2[ ] :

This statement is used to move the entire data from one ITAB1 to another ITAB2.

Syntax:

ITAB1[ ]  =  ITAB2[ ].

15. COLLECT :

This statement checks weather the WA record already exists with the same key.

If yes, it just add numerical fields.

If no , it will append the new record.

Same key means , Same Character Fields. i.e; C , N , D , T.

Numerical fields means  I , F  , P.

Syntax:

TYPES  OF  TABLES :

      1. Transparent Tables.

      2. Pool Tables.

      3. Cluster Tables.

Comparison of Transparent, Pool and Cluster tables:

Transparent	Pool	Cluster
Contain a single table. Used to store master data	They are used to hold a large number of very small tables(stores system data)	They are used to hold data from a few number of large tables.(stores system data)
It has a one-to-one relationship with a table in the database	It has a many-to-one relationship with a table in the database	It has a many-to-one relationship with table in the database
For each transparent table there is one associated table in the   database	It is stored with other pooled tables in a single table called table pool in the database	Many cluster tables are stored in a single table in the database called a table cluster
The database table has the same name, same number of fields and the fields have the same names	The database table has different name, different number of fields and fields have different names	The database table has different name, different number of fields and fields have different names
There is only a single table	Table pools contain more tables than table clusters	Contains less tables than table pools
Secondary indexes can be created	Secondary indexes cannot be created	Secondary indexes cannot be created

TYPES  OF  INTERNAL TABLES :

There are three types of Internaltables.

1. STANDARD internal Tables.

2. SORTED internal Tables.

3. HASHED internal Tables.

STANDARD	SORTED	HASHED
These are the default internal tables which are created by us. We use either key operation (or) index operation to read a record. We use either linear search (or)   Binary search for reading record. If use Binary Search, the response time will be Resp.Time  =  Log(N). We can append , insert the records whenever we want. We can sort the data based on our own conditions.	These are special ITAB's where the data is automatically sorted when ever a new record is added. We use either key(or) index operation to read a record. We use only Binary search for reading a record, bcoz the data is automatically sorted. The Response  Time will be same. The main disadvantage is , we can not sort ITABS based on our conditions, bcoz the data is already sorted.	These are also special type of   ITAB which should be used when working with large data sets(Bulk amount of data). Here, we use only Keyoperation, but not the index  operation. It uses Hashed algorithm for reading a record. The Resp.Time is always fixed regardless of the total no of records. In Real-Time , we hashed ITAB's only whenever we work with server to server communication like transferring the data from ABAP to BI server.

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