DB2 DDS Database Tutorials

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DB2/400

Objective

To make the participants familiar with the DB2/400 concepts which includes creation of Physical

Files, data entry using DFU, creation of views and interactive SQL/400 sessions.

Features of DB2/400

DB2/400 is an RDBMS which comes installed along with the system. The whole of the DB2/400

component is an integral part of the LIC. DB2/400 supports upto 11 CODD rules and thus is a

very strong RDBMS. There are primarily two types of files that can be created on the AS/400.

They are :

1) Physical Files and

2) Logical Files

These files can be comfortably accessed from any of the High Level Languages used on the

AS/400 like RPG/400, CL/400, COBOL/400, C/400, etc. The data integrity is maintained

through various database constraints and triggers.

Data Types in DB2/400

The following are the prime data types supported by DB2/400. They can be represented by a

single character assigned for each data type in the column of data type in the DDS.

A – alphanumeric – 32766 characters

P – packed decimal – 31 digits, 30 decimal positions

S – zoned decimal - 31 digits, 30 decimal positions

L – Long date – 4 bytes

Z – Time stamp – 10 bytes

T – Time – 6 bytes

F – Floating point – 1 – 9 digits in single precision & 1 – 17 digits in double precision

H – Hexadecimal – 32766 bytes

Physical Files

A physical file is an AS/400 object with the object type *FILE and the attribute PF. A physical

file is composed of three components, namely,

1) Record Format

2) Access Path

3) Data Members

1) Record Format – It comprises of the formal definition of the fields and their respective

attributes within the file. It is normally coded using the DDS keywords through the SEU.

2) Access Path – It defines the path as to how the records in the Physical File would be

accessed.

3) Data Members – It is this segment of the Physical File which stores data physically. One PF

can have many data members, each data member in turn having many records in it. However,

all the data members share the same record format and the access path.

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This architecture can be represented pictorially as follows:

The maximum length of the record format cannot exceed 32766 bytes. A physical file can have

maximum of 120 key fields. It can have a maximum of 32766 members. The maximum no. of

fields that a PF allows is 8000.

The record format can be described using the SEU and the DDS keywords. A physical file can be

created using the command

CRTPF (FILE/LIBRARY)

This creates an object of the type *FILE and with the special attribute as PF-DTA. Such a PF has

the default no. of members as 1 and the maximum no. of records as 10000 and an extended

capacity of 1000 incremented thrice (that is, 13000 records). However, by pressing F4, we can

change the options and specify the desired values.

The members can be added by using the command ADDPFM. Change to the members can be

made by CHGPFM. Deletion of a member is possible through RMVM.

Data entry into a PF can be made in three ways, viz.,

1) DFU – Data file utility – The command is STRDFU. This supports insert, update

delete of the records, but only one at a time.

2) IDDU – Interactive Data Definition Utility – The command is STRIDD.

3) Interactive SQL – STRSQL is the command to start an SQL session and using the

DML commands, data manipulation can be achieved.

The records can be viewed using the RUNQRY command

RUNQRY QRYFILE(LIBRARY/FILE)

Suppose, a change in the PF structure is required after data entry, we can change it through the

SEU and re-compile it but the entire data is lost in this case as the object is deleted and recreated.

RECORD FORMAT

ACCESS PATH

DATA

MEMBER

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So, an alternative for this is the command CHGPF where in the options for mapping and dropping

the fields can be specified. This however retains the data to the maximum possible extent and

any data entry made thereafter is appended to the previous data.

To copy the PF object the command used is CPYF which has got various options for specifying

the source and the destination files and also to create/replace the file and its members and also to

map/drop the fields.

The other commands related to the PFs are :

CLRPFM – Clears the PF member.

DLTF – Deletes the PF object.

DSPPFM – Displays the records in physical file member.

DSPFFD – Displays the file field information.

DSPDBR – Displays the data base relation with other files.

Physical File Keywords

The keywords define the special attributes of every field and are entered in the function column in

the DDS. There are 4 levels of keywords that can be defined in the PF, viz.,

1. File Level

2. Record Level

3. Field Level

4. Key field Level

1) File Level – Keywords entered at the file level, i.e., before any other line of code in a

PF, are known as file level keywords.

The file level keywords are :

UNIQUE – Defines the key field entry as unique, i.e., no duplicate key values could

exist in the PF.

FIFO – First In First Out – The records within the group of repetitive key field data

retrieved in the order they were ordered..

LIFO – Last In First Out – The records within the group of repetitive key field data

are accessed in the reverse order of their entry.

REF – Gives the reference to some other Physical File which can be used to refer to

the fields individually for their attributes.

2) Record Level – Keywords entered at the Record Format Level.

The record level keywords are :

FORMAT – When you want to refer to the entire format of a pre-existing PF we use

this keyword. However the record format name can be changed, and also the key

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field can be changed provided it is one of the existing fields. Defining any fields

while using this keyword will result in a compile time error.

TEXT – Is used to provide some documention/description to the file.

3) Field Level – These keywords are provided at the respective field level.

COLHDG – Column Heading – Once specified, can be used in reports and screens.

COLHDG(‘Employee Code’)

The column heading ‘Employee Code’ Will appear in report and screens.

COLHDG(‘Employee’ ‘Code’) the heading will appear in two lines.

COMP – Compares the value entered with that specified along with this keyword.

Data entered in the field must satisfy condition specified in COMP keyword otherwise system

restricts and gives error.

COMP(GT 6000) value in this field must be greater than 6000.

The operators like GT are

LT = Less Than

EQ= Equal

NE=Not Equal

LE=Less than equal

GE=Greater than or equal

VALUES – Allows data entry of only the specified values.

RANGE – Allows data entry between the specified range of values only.

CHECK – Checks for mandatory entry or mandatory fill or both for a given field.

This keyword can be specified only against character type of field.

CHECK(ME) stands for mandatory entry. That means this field can not be left with null.

CHECK(MF) stands for mandatory fill. User must enter data full of this field.

DFT – Specifies a default value for a field when a value has not been entered.

REFFLD – Allows to specify the reference of a given field from an external file other

than the one specified at the REF.

TEXT – A description for the field can be specified here.

ALIAS – Allows the entry of an alternative name for a field.

4) Key-field Level – These keywords are specified at the key-field level.

DESCEND – Processes the records in the descending order of the key value.

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ABSVAL – Allows only absolute value entry into the key field.

DIGIT – Sorts the records based on the numeric value in the alphanumeric key field.

SIGNED – Sorts the records based on the signed value of the key field value.

Columns . . . : 1 71 Edit STDLIB/MANSAM

SEU==> MASTERT

FMT PF .....A..........T.Name++++++RLen++TDpB......Functions++++++++++++++++++

*************** Beginning of data *************************************

0001.00 A UNIQUE

0002.00 A R MASTREC TEXT(‘MASTER FILE’)

0003.00 A ACCNO 5P 0

0004.00 A ACCTYPE 1A VALUES('R' 'S')

0005.00 A ACCNM 20A COLHDG(‘CUSTOMER NAME’)

0006.00 A ACCADD 40A

0007.00 A ACCBAL 10P 2

0008.00 A OPENBAL 10P 2

0009.00 A ACCOPDATE L

0010.00 A ACCSTATUS 1A VALUES('O' 'C')

0011.00 A DURATION 3P 0 VALUES(12 24 36)

0012.00 A K ACCNO DESCEND

****************** End of data ****************************************

Constraints

A PF can be applied with various constraints which can be added by the command ADDPFCST.

There are four kinds of constraints which can be applied to a PF. They are:

1) Primary Key – specified by *PRIKEY option

2) Reference (Foreign key) – specified by *REFCST option

3) Check Constraint – specified by *CHKCST

4) Unique Key – specified by *UNQCST option

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SEU==> TRANST

FMT PF .....A..........T.Name++++++RLen++TDpB......Functions++++++++++++++++++


0001.00 A UNIQUE FIFO

0002.00 A R TRANREC TEXT(‘TRANSACTION FILE’)

0003.00 A TACCNO 5P 0

0004.00 A TRANTYPE 1A VALUES('D' 'W')

0005.00 A TRANAMT 10P 2 CHECK(ME)

0006.00 A DATEOFTRAN L DATFMT(*EUR)

0007.00 A K ACCNO

****************** End of data ****************************************

Logical Files

A logical file is a database file used to view data stored in one or more physical files in the

desired manner. It is an AS/400 object of the type *FILE and attribute LF. The features of

logical files are :

1) They don’t physically contain data.

2) Access path can be changed as per the requirement.

3) A PF can be processed by multiple LFs.

4) Two or more LFs may share the same access path.

5) Records could be selected or omitted from the PF in a specified criteria.

6) LFs can have more than one record format but each record format must relate to one

or more PFs and include at least one key field. The record format lengths may vary.

7) An LF with multiple record format may process the data from more than one PF

treating them as data from a single file.

8) The PF fields’ attributes may be changed in an LF but the data in the PF is not

affected.

9) A maximum of 32 PFs can be joined or unionized using these files.

There are two broad categories of Logical Files, viz.,

a) Non-Join Logical Files and b) Join Logical Files

Non-Join Logical Files

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A non-join logical file processes each record individually from one or more physical files. A

non-join logical file can have from 1 to 32 record formats. It can be used for record update in

case it is referring to just one PF. In addition to the 4 levels of keywords used in PF, there is one

select/omit level keyword in non-join logical files.

1) File level – Apart from that used in the PF an additional keywords DYNSLT and

ACCPTH are used. DYNSLT is used to specify the dynamic selection and omission

criteria. ACCPTH is used to refer to the access path from some other PF.

2) Record level – PFILE is used to specify which PF/PFs the LF is referring to. A

maximum of 32 PFs could be referred to in a LF.

3) Field level –

CONCAT – used to concatenate two or more fields.

SST – used to substring a field.

RENAME – used to rename an existing field of PF.

4) Key-Field level – They are the same as applicable for a PF.

5) Select/Omit level – When the DYNSLT is used at the FILE level, the S or O options

are specified at the select/omit level to specify the dynamic selection/omission

criteria of records from the PF. However, the S should always follow the occurance

of O. Two consecutive O or S or a combination of them implies an OR condition,

whereas, one O or S followed by another condition is an AND condition.

Union

Records from multiple PFs having a common record format accessed together in a non-join

logical file is called a Union. This can be put in three different ways :

1) All the PFs involved should have exactly the same record format.

2) The record format of one PF is a part of the record format of another PF.

3) Both the files may be having totally different record format but the common fields

are put together in the UNION.


SEU==> TRALF

FMT LF .....A..........T.Name++++++RLen++TDpB......Functions++++++++++++++++++


0001.00 A R TRANREC PFILE(STDLIB/TRANST)

0002.00 A K DATEOFTRAN

****************** End of data ****************************************

Note : This will create a non-join logical file on a single PF and includes all fields from the

record format of TRANST.

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SEU==> TRALF



0001.00 A R TRANREC PFILE(STDLIB/TRANST)

0002.00 A ACCNO RENAME(TACCNO)

0003.00 A DATEOFTRAN

0004.00 A K DATEOFTRAN

****************** End of data ****************************************

Note : This will create a non-join logical file on a single PF and includes only the named fields

from the record format of TRANST.


SEU==> TRALF



0001.00 A R TRANREC PFILE(TRANST1 TRANST2)

0002.00 A FORMAT(TRANST1)

0003.00 A K TACCNO

****************** End of data ****************************************

Note : This will create a non-join logical file on a multiple PFs (assuming TRANST1 TRANST2)

and includes the record format from TRANST1. This is also a type of a UNION.

Join Logical Files

Fields from multiple PFs put together to form a record format based on a common field which

may have same or different name but common attributes is known as a Join Logical File. Such

files are read-only files. There can be only one record format for a join logical file. The levels of

keywords in the join logical file are file level, record level, join level, field level, and key field

level keywords.

1) File Level – Same as PF.

JDFTVAL – Used to create a special type of Join Logical File discussed later.

2) Record Level – In addition to that used in the PF, we use,

JFILE – Used to join the different files. Maximum 32.

3) Join Level –

JOIN – Used to specify the join in between any two files used in the JFILE.

JFLD – Used to specify the field on which the files are being joined.

JDUPSEQ – Used to process the records from PF that have duplicate join fields.

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4) Field Level –

JREF – It is used to refer to the definition of a field defined in one of the PFs

involved in the join.

5) Key Field level – Same as PF.

There are two types of Join Logical files, viz., Intersection and Left Outer Join.

Intersection – By default, the Join Logical file is an intersection.

Left Outer Join – By specifying the keyword, JDFTVAL at the file level, we achieve a left outer

join. In this case, the records of the primary file which do not have a secondary match are also

included in the join and the fields are padded with default values.

DEPARTMENT :

----------------

0001.00 A UNIQUE

0002.00 A R DEPTREC

0003.00 A DEPTNO 2P 0

0004.00 A DEPTNAME 10A

0005.00 A LOCT 10A

0006.00 A K DEPTNO

EMPLOYEE1 :

-----------------

0001.00 A UNIQUE

0002.00 A R EMPREC

0003.00 A EMPCD 5P 0

0004.00 A EMPNM 20A

0005.00 A DEPT 2P 0 COLHDG('DEPARTMENT')

0006.00 A BASIC 7P 2

0007.00 A DA 7P 2

0008.00 A SEX 1A VALUES('M' 'F')

0009.00 A K EMPCD DESCEND

0010.00 A K DEPT

DYNSLT CONCEPT :

----------------------

0001.00 A DYNSLT

0002.00 A R JOINREC JFILE(DEPARTMENT EMPLOYEE1)

0003.00 A J JOIN(DEPARTMENT EMPLOYEE1)

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0004.00 A JFLD(DEPTNO DEPT)

0005.00 A DEPTNO

0006.00 A DEPTNAME

0007.00 A LOCT

0008.00 A EMPCD

0009.00 A EMPNM

0010.00 A TEMP 1 I SST(EMPNM 1 1)

0011.00 A SEX

0012.00 A K DEPTNO

0013.00 A* K EMPCD

**NOTE:2 KEY FIELDS NOT TO BE SPECIFIED**

0014.00 A S DEPTNO COMP(EQ 10)

0015.00 A S TEMP VALUES('M')

***************************************************

JDUPLICATE SEQUENCE :

-----------------------------

0001.00 A DYNSLT



0004.00 JFLD(DEPTNO DEPT)

0005.00 JDUPSEQ(EMPCD *DESCEND)

0006.00 A DEPTNO

0007.00 A DEPTNAME

0008.00 A LOCT

0009.00 A EMPCD

0010.00 A EMPNM

0011.00 A TEMP 7 I SST(LOCT 1 7)

0012.00 A SEX

0013.00 A K DEPTNO

0015.00 A S DEPTNO COMP(EQ 10)

0017.00 A S TEMP VALUES('UNIT112')

JDFTVAL :

0001.00 A JDFTVAL

0002.00 A DYNSLT



0005.00 JFLD(DEPTNO DEPT)

0006.00 JDUPSEQ(EMPCD *DESCEND)

0007.00 A DEPTNO

0008.00 A DEPTNAME

0009.00 A LOCT

0010.00 A EMPCD

0011.00 A EMPNM

0012.00 A TEMP 7 I SST(LOCT 1 7)

0013.00 A TEMP1 1 I SST(EMPNM 1 1)

0014.00 A SEX

0015.00 A K DEPTNO

0017.00 A O TEMP1 VALUES('S')

0018.00 A S DEPTNO COMP(GT 10)

0019.00 A S TEMP VALUES('UNIT112')

*******************************************************************************

SELFJOIN : A Join is formed on the same PF.

0001.00 A R JOINREC JFILE(SELFPF SELFPF)

0002.00 A J JOIN(1 2)

0003.00 JFLD(MGRCD EMPCD)

0004.00 A EMPCD JREF(1)

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0005.00 A DEPT JREF(1)

0006.00 A EMPNM JREF(1)

0008.00 A MGRCD JREF(1)

0009.00 A MGRNM JREF(2) RENAME(EMPNM)

0010.00 A K EMPCD

SELFPF :

INPUT FILE :

EMPCD EMPNM DEPARTMENT BASIC MGRCD

1 MANISH 10 141.34 50

2 RAJESH 20 992.92 50

3 YOGESH 10 992.82 60

4 RAJ 30 2,511.12 60

5 UNMESH 20 992.02 50

50 BARU 40 70,000.00 70

60 RAJU 40 45,456.55 70

70 BHARAT 50 99,999.99 70

OUTPUT RESULT :

EMPCD EMPNM DEPARTMENT BASIC MGRCD MGR NAME

1 MANISH 10 141.34 50 BARU

2 RAJESH 20 992.92 50 BARU

3 YOGESH 10 992.82 60 RAJU

4 RAJ 30 2,511.12 60 RAJU

5 UNMESH 20 992.02 50 BARU

50 BARU 40 70,000.00 70 BHARAT

60 RAJU 40 45,456.55 70 BHARAT

70 BHARAT 50 99,999.99 70 BHARAT

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