logical databse

7/30/2019 Logical Databse

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Logical Database


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What is Logical Database ?

A logical database is a special ABAP/4 program

which combines the contents of certain databasetables.

Using logical databases facilitates the process of

reading database tables.


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Logical Databases - Views of DataA logical database provides a particular view ofdatabase tables in the R/3 System.

The data structure in a logical database is

hierarchical.Many tables in the R/3 System are linked to eachother using foreign key relationships.

Some of these dependencies form tree-like

hierarchical structures. LDBs read data fromdatabase tables that are part of these structures.


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Using LDB

There are two ways of using a LDB :

By linking it with an executable program.

By using the function module LDB_PROCESS in any

ABAP program.


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Linking LDB with executable program

By entering the name of the logical database in the

program attributes

The subroutines of the logical database program andthe event blocks of the executable program form a

modularized program for reading and processing

data.

The runtime sequence is controlled by the structure,selections, and PUT statements in the LDB, and by

the GET statements in the executable program.


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Events in LDB Programming

GET

GET LATE


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GET EventThis is the most important event for executableprograms that use a LDB.

It occurs when the logical database has read a line

from the node and made it available to theprogram in the work area declared using thestatement NODES .

You can process the data in the work area in thisevent block. For example, you can write it directly toa list, or store it in a sequential dataset (internal tableor extract) so that you can process it later.


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Get Late Event

This event is triggered when all of the data records

for a node of the logical database have been read.

You can use the event block for processing steps that

should occur at the end of the block, like, for

example, calculating statistics.


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HR LDBs

PNP - Evaluates all HR Master Data and time data.

PAP - Applicant Master Data

PCH - Personnel Planning


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Functions

Standard Selection Screen

Data Retrieval

Authorization check


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Selection Screen

LDB provides a standard selection screen

which gives standard look and feel throughoutall programs


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Date Selection

Date selection delimits the time period for which data

is evaluated.

GET PERNR retrieves all records of the relevant

infotypes from the database . When you enter a

date selection period, the PROVIDE loop retrieves

the infotype records whose validity period overlapswith at least one day of this period.


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Person selection

Person selection is the 'true' selection of choosing a

group of employees for whom the report is to run.


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Sorting Data

The standard sort sequence lists personnel numbers in

ascending order.

SORT function allows you to sort the report data

otherwise. All the sorting fields are from infotype

0001.


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Report Class

You can suppress input fields which are not used on

the selection screen by assigning a report class toyour program.

If SAP standard delivered report classes do not satisfy

your requirements, you can create your own report

class through the IMG.


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Report CategorySelection Screen can be customised by use of Report

Category

Able to show/remove/hide certain standard selection

criteria

Able to set selection periods eg As At Date

Able to turn Org Structure button on/off.

In SE38

Change Program Attributes

Click HRReport Category Create

This button only appears in PNP


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Report CategorySteps to create new:

Click new entries

Enter report category and descriptionCheck Org Structure allowed for org struc button

Interval for Date period range.

Double click Allowable Selection Criteria

Click New EntriesSelect entries from pull down list


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Report Category

Selections which are not available must be coded in

your program as additional selection criteria.

Save

Back

Include report category in your program

Re-activate program

Run and test it out.


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Programming using LDB

An HR report which uses the LDB has the followingbasic structure.

Report sampleTables: PERNR.

INFOTYPES: 0001.

GET PERNR.

PROVIDE * from p0001 between pn-begdaand pn-ennda.

Write : / p0001-pernr, p0001-stell, p0001-begda.

END PROVIDE.


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PERNR

Pernr is a data dictionary structure without a

database. You must declare this structure in thereport using the tables statement.


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All infotypes to be processed in the report are listed

in the abap INFOTYPES keyword.

The database usually contains several records with

different validity periods and not just one record for

each infotype and personnel number.

Therefore, the infotypes statement is used to create

an internal table for each of the listed infotypes. The

structure of this table corresponds to that of therelevant infotype.

Infotype declaration


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Data Retrieval

Data is retrieved at the GET PERNR event. The Get

pernr action is executed for all personnel numbers

that were selected on the basis of selection screen

entries.It fills the internal tables of infotypes that are

declared for each employee using the infotypes

statement.

The internal infotype table is filled with all recordsexisting between the lowest and highest system date.

The internal table has the name pnnnn, where nnnn

is the infotype number.


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After the Get pernr event, the internal tables of the

infotypes contain records and are ready for

processing.

Internal tables are generally processed line-by-line

using the loop statement


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Processing Infotype Records

Processing of infotype records is time-dependent, by

this we mean dependent on the data selection and

period entered on the processed at the same time

and made available for a specific partial period.It is processed with the provide statement.

The syntax is,

Provide * from pnnnn between pn-begda and pn-

endda.

Write : / pnnnn-field.

Endprovide.


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Nnnn stands for the four digit infotype number. The

relationship between the infotype and the dataselection period of the selection screen is established

using the pn-begda and pn-endda variables.

In the provide loop, the data of an infotype record is

available for processing in the pnnnn structure.


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You often only require the most recent or earliest

infotype record, not all infotype records.

In this case, use one of the following statements,RP-PROVIDE-FROM-LAST pnnnn space pn-begda

pn-endda.

Or

RP-PROVIDE-FROM-FIRST pnnnn space pn-begdapn-endda.


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These statements make the most recent of earliest

record in the pn-begda to pn-endda data selection

period available in the structure pnnnn for infotype

nnnn.

If the infotype has subtypes, replace the space

parameter by the appropriate subtype number

When a record has been successfully read, the return

code PNP-SW-FOUND = 1 is returned.


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Example report

Report sample.

Tables : pernr.

Infotypes : 0001.

Get pernr.RP-PROVIDE-FROM-LAST P0001 SPACE PN-BEGDA

PN-ENDDA.

If PNP-SW-FOUND = 1.

Write : / p0001-stell, pn-begda, pn-endda.Else.

Reject.

Endif.


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HR Transactions


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HR Master Data

PA40 Personnel Events

PA30 Maintain HR Master DataPA10 Personnel File

PA20 Display HR Master Data


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Applicant Master Data

PB10 Init.entry of applicant master data

PB20 Display applicant master dataPB30 Maintain applicant master data

PB40 Applicant events


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