MIS 3020 ABAP Programming

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MIS 3020 ABAP Programming

• Lecture 2
• Elementary User Defined Types
• Domains, Elements, Variables/Fields

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Objectives

• To introduce
• ABAP elementary and user defined data types
• keywords used to declare data items
• complex record structures
• the use of internal tables in ABAP
• declaring an internal table
• populating fields of an internal table
• the ABAP data dictionary
• domains, elements tables
• integrity constraints

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ABAP Data TypesElementary Data TypesUser
Defined Types
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ABAP Data Types Structures

• Elementary Types supported by ABAP
• characters
• numbers
• Date
• Time
• Hexadecimal
• Non- Elementary Types (User Defined Structures)
• records
• internal tables

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Character Types

• c character
• default type when none is specified
• used for regular text information
• pads right end with spaces
• n numeric text
• contains strings of digits
• used for numbers that are used for identification
  and as sort criteria for internal tables
• house numbers, postcodes, phone numbers, ...
• pads left end with zeros

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Number Types

• i integers
• fixed length of 4 bytes
• possible values range from 2-31 to 231-1
• p packed
• numbers stored in compressed formats, ie, 2
  digits per byte of storage.
• can be used for all types of calculations
• f floating point
• possible range from 1E-307 to 1E307
• can be used in all types of calculations but
  beware of rounding errors. (Dont use in eq
  condition tests)

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Date Type

• d date
• fixed length of 8 and internal representation of
  YYYYMMDD
• several output formats supported
• set default output format in your User
  Profile/Defaults
• can specify different/specific output format when
  writing value out
• supports date arithmetic

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Time Type

• t time
• fixed length of 6 and format HHMMSS
• several output formats supported
• can specify different/specific output format when
  writing value out
• supports time arithmetic

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Hexadecimal Type

• x hexadecimal
• values in hexadecimal fields are stored in
  binary (bit stream) format
• eg F089 would be stored as 1111000010001001
• 2 hex digits are stored in 1 storage byte

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Elementary Types Default Lengths and Values

• Type Length Initial Value
• c 1 space
• n 1 0
• i 4 0
• p 8 0
• f 8 0.0
• d 8 00000000
• t 6 000000
• x 1 X00

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The ABAP Statement

• most ABAP statements begins with a reserved
  keyword, e.g. data, types, select
• all end with a period (.)
• can combine a sequence of statements starting
  with the same keywords into a single statement
  using colon and comma (for most keywords)

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The data keyword

• variables are declared using the data keyword
• data varname(len) type typedef value val.
• data postcode(4) type n value 4001.
• data counter type i value 1.
• data price type p decimals 2.
• data varname like objname value val.
• where objname is a previously declared item (or
  database object)
• data DOB like sy-datum.

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The data statement

• multiple variable declarations can be made in the
  same data statement by using data
• data DOB like sy-datum, counter type i.

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The parameters keyword
PARAMETERS ltfieldgt TYPE lttypegt DEFAULT ltvaluegt.
PARAMETERS P1 TYPE P,
P2(6) TYPE C DEFAULT ITB255.
X
P1
P2
ITB255
Selection Screen
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The constants keyword

• Constants are declared like fields with the
  addition of the value clause.
• constants max_counter type i value 9999.
• A constant cannot be changed
• trying to change the value of a constant will
  result in a runtime error (if the change can only
  be detected at runtime, ie, if the constant is
  used as an actual parameter)

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Records (or Structures)

• records consist of a fixed number of data objects
  called components of the record
• declared using data begin of and data end of
• data begin of student,
• stnum(8) type n,
• stname(25) type c,
• stDOB like sy-datum,
• stphone(12) type n,
• end of student.

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Working With Records

• components of records are referenced by
  recordname-componentname
• data IT_student like student.
• student-stnum 12345678.
• student-stname F.Jones.
• student-stDOB 19790623.
• student-stphone 3221 1278.
• move student to IT_student.

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The types keyword

• used to create a user defined type
• types begin of student_type,
• stnum(8) type n,
• stname(25) type c,
• stDOB like sy-datum,
• stphone(12) type n,
• end of student_type.
• data student_rec type student_type,
• student_tab type student_type occurs 0.

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The tables keyword

• tables lttablestructureviewgt, e.g. tables spfli
• Creates a structure in the program work area with
  the same
• name
• row structure
• field names, datatype, sequence
• as the referenced database table, structure or
  view

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Internal Tables

• used as
• snapshots of database tables
• containers for volatile data
• exist only at runtime, (unlike database tables)
• consist of any number of records
• declared using occurs n
• data student_tab like student occurs 0.
• data student_tab like student occurs 0 with
  header line.
• note that it is not necessary to declare the
  exact size of the table SAPs memory management
  allows the table to be infinitely extensible.

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Internal Tables with header line
a record structure of the same name is
automatically created
Program Work Area
R/3 Database
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Internal Tables without header line
need to define a record structure explicitly
in your abap program
Program Work Area
R/3 Database
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Internal Tables - header lines

• advantages of header lines
• convenient declaration
• table and header line structure declared in same
  statement
• ease of use
• dont have to explicitly move data into the work
  area structure and then append the work area
  structure to the table
• some statements require a table with header line
• disadvantages of header lines
• performance - I/O is faster for tables without
  header line
• cannot use in embedded structure

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Internal Tables - header lines

• default declaration is without a header line
• to declare a table with a header line
• data itab type tabtype like objname
  occurs n with header line
• data book_tab like sbook occurs 0 with header
  line.

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More Complex Structures

• It is possible to create nested structures
• a structure can contain another structure
• a record can contain an internal table as one of
  its components
• a table can contain another table, etc

• types begin of addr_type,
• city(25),
• street(30),
• end of addr_type,
• begin of person,
• name(25),
• address type addr_type,
• end of person.
• data emp type person.
• emp-address-city Sydney.

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The Data DictionaryDomainsData ElementsTables
Structures
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3 Levels of the Dictionary

• Tables or Structures
• composed of one or more fields
• Data Elements
• each field refers to a data element that
  describes the meaning of the field
• Domain
• determines the technical properties of the field
• data type and size (including number of decimal
  places)
• allowed data values
• output characteristics

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Elements and Domains

• Domain
• provides the technical description
• Element
• determines the role played
• create a domain called ID_Number
• create elements Student_ID and Staff_ID based on
  the ID_Number domain

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Referential Integrity Check
Referential Integrity Check
Data Element Definition
Data Element Definition
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Field Information
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Domain Definition
Define the text to be displayed on screen
or report
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Range/Value Integrity Check
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Integrity Checking

• Domain Range/Value Integrity Checks
• value table
• only values contained in the value table can be
  entered in fields referring to this domain
• fixed values
• only values that match a value in the user
  specified list of admissible values can be
  entered in fields referring to this domain

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Integrity Checking

• Referential Integrity Checking
• check table
• foreign key values must match an entry in the
  specified check table
• check tables bound to input fields on data entry
  screens
• position the cursor on input field and press F4
  to get a list of permissible values
• the default check table for a field is the value
  table of the underlying domain
• from the Dictionary Table/Structure Display
  Fields screen, Select GoToForeign Keys (F8)

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Foreign Key value must match
Primary Key value of the check table
Cardinality Ratio of Foreign Key
Scroll Through Other Defined Foreign Keys
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Viewing the Contents of a Database Table

• From the
• Data Dictionary
• Click on the Table Radio Button enter the Table
  Name
• From the Dictionary Table Table/Structure
  Display Fields screen choose UtilitiesTable
  Contents
• Data Browser (from main menu item Overview)
• Enter the Table Name
• Choose TableTable Contents or press Enter
• Fill in the appropriate Selection Screen entries
• Click on the Execute icon on the application
  toolbar, (or press F8)

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Number of Rows Selected
Table Name
Sort Buttons
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Conclusion

• This lecture covered aspects of
• defining identifiers in an ABAP program
• the data dictionary
• In particular we covered the basic data types
  supported by ABAP
• character, number, integer, float, packed, date,
  time, hexadecimal
• We also discussed user defined structures
• records, tables

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Conclusion

• User defined structures are declared using the
  types keyword.
• Identifiers are declared using
• the data keyword
• the parameters keyword
• Constants are declared using the constants
  keyword.
• The datatype of an identifier can be specified
  using
• type specific type
• like previously defined identifier/dictionary
  object

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Conclusion

• Structures
• records defined by data begin of / data end of
• internal tables defined using occurs
• complex structures can be created by nesting
  records and internal tables

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Conclusion

• The second half of the lecture covered
• Data Dictionary
• Organization of Data in the Dictionary
• Domain ? Elements ? Tables/Structures
• Using the Dictionary to see
• the definitions of Domains, Elements, Tables
• the contents of Tables
• How the Dictionary maintains Value and
  Referential Integrity

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Related Reading

• Online Help
• R/3 Library ...Basis Components ... ABAP
  Workbench
• BC ABAP Users Guide
• The ABAP Programming Language Basic Statements
  Declaring Data Creating Data Objects and Data
  Types
• The DATA Statement
• BC ABAP Dictionary Tables
• BC ABAP Dictionary Data Elements
• BC ABAP Dictionary Domains