Selection part of Logical Database

Question

I read about logical database somewhere on the net but it was not so clear. Can anyone explain to me about the selection part of the logical database???

Answer 1

Logical databases are special ABAP programs that retrieve data and make it available to application programs. The most common use of logical databases is still to read data from database tables and linking them to executable ABAP programs while setting the program contents. You edit logical databases using the Logical Database Builder in the ABAP Workbench.
However, since Release 4.5A, it has also been possible to call logical databases independently of this tool using the function module LDB_PROCESS. This allows you to call several logical databases from any ABAP program, nested in any way. It is also possible to call a logical database more than once in a program, if it has been programmed to allow this. This is particularly useful for executable programs, allowing them to use more than one logical database and process a database more than once.
Logical databases contain Open SQL statements that read data from the database. You do not therefore need to use SQL in your own programs. The logical database reads the program, stores them in the program if necessary, and then passes them line by line to the application program or the function module LDB_PROCESS using an interface work area.
http://help.sap.com/saphelp_nw2004s/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/content.htm
A logical database is a special ABAP/4 program which combines the contents of certain database tables. You can link a logical database to an ABAP/4 report program as an attribute. The logical database then supplies the report program with a set of hierarchically structured table lines which can be taken from different database tables.
GO THROUGH LINKS -
http://www.sap-basis-abap.com/saptab.htm
http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9bfa35c111d1829f0000e829fbfe/content.htm
http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm
http://help.sap.com/saphelp_nw04/helpdata/en/c6/8a15381b80436ce10000009b38f8cf/frameset.htm
/people/srivijaya.gutala/blog/2007/03/05/why-not-logical-databases
Re: **LDB**
www.sapbrain.com/FAQs/TECHNICAL/SAP_ABAP_Logical_Database_FAQ.html
www.sap-img.com/abap/abap-interview-question.htm
www.sap-img.com/abap/quick-note-on-design-of-secondary-database-indexes-and-logical-databases.htm
http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/content.htm
http://help.sap.com/saphelp_nw2004s/helpdata/en/9f/db9bb935c111d1829f0000e829fbfe/content.htm
Logical databases are SAP standard programs that are desinged with selections screens that helps easy retrival and access of data from various tables in and efficient manner.
You can get to know more about the logical databases from the SAP documentation or the following links.
A logical database is a special ABAP/4 program which combines the contents of certain database tables. You can link a logical database to an ABAP/4 report program as an attribute. The logical database then supplies the report program with a set of hierarchically structured table lines which can be taken from different database tables.
Advantages of Logical database -
1) No need of programming for retrieval , meaning for data selection
2) Easy to use standard user interface, have check completeness of user input.
Disadvantages
1) Fast in case of lesser no. of tables But if the table is in the lowest level of hierarchy, all upper level tables should be read so performance is slower.
GO THROUGH LINKS -
http://www.sap-basis-abap.com/saptab.htm
http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9bfa35c111d1829f0000e829fbfe/content.htm
http://help.sap.com/saphelp_nw04/helpdata/en/9f/db9b5e35c111d1829f0000e829fbfe/frameset.htm
http://help.sap.com/saphelp_nw04/helpdata/en/c6/8a15381b80436ce10000009b38f8cf/frameset.htm
1. A logical database is in fact
a program only.
2. This LDB provides two main things :
a) a pre-defined selection screen
which handles all user inputs and validations
b) pre defined set of data
based upon the user selection.
3. So we dont have to worry about from
which tables to fetch data.
4. Moreover, this LDB Program,
handles all user-authorisations
and is efficient in all respects.
5. tcode is SLDB
good info about Logical Database. you can check the link.
http://www.geekinterview.com/question_details/1506
http://help.sap.com/saphelp_46c/helpdata/EN/35/2cd77bd7705394e10000009b387c12/frameset.htm
Re: How to Create and Use ldb in reports?
Re: Logical databases
http://help.sap.com/saphelp_46c/helpdata/en/9f/db9bed35c111d1829f0000e829fbfe/frameset.htm
Functions for displaying and changing logical databases:
Call Transaction SE36 or
Choose ABAP Workbench -> Development -> Programming environ. -> Logical databases
Interaction between database program and report:
During program processing, subroutines are performed in the database program and events are executed in the report.
To read data from a database tables we use logical database.
A logical database provides read-only access to a group of related tables to an ABAP/4 program.
advantages:-
The programmer need not worry about the primary key for each table.Because Logical database knows how the different tables relate to each other,and can issue the SELECT command with proper where clause to retrieve the data.
i)An easy-to-use standard user interface.
ii)check functions which check that user input is complete,correct,and plausible.
iii)meaningful data selection.
iv)central authorization checks for database accesses.
v)good read access performance while retaining the hierarchical data view determined by the application logic.
disadvantages:-
i)If you donot specify a logical database in the program attributes,the GET events never occur.
ii)There is no ENDGET command,so the code block associated with an event ends with the next event
statement (such as another GET or an END-OF-SELECTION).
1. transaction code SLDB.
2.enter name z<ldb-name>
3.create
4.short text
5.create
6. name of root node (here Ekko)
7. enter short text (f6)
8.node type -> data base table.
9.create
10 change logical DB
riht click on ekko and insert node
here node name ekpo
11.create
12. click on selections
13. press no Should the changed structure of Z<ldb name> be saved first.
14.select tables which you want to join.
15.transfer
16 now you have to o to coding part.
17. save
activate.
19.click to src code
double click on first include and activate
Regards
Vasu