data dictionary

[Former Member]

hi experts,

what is mean by primary key in the data base table ? what is the main purpose of that? with out primary what happens.

in custom table how many primary keys we can put maximum? at what basis we have to take primary key?

give me the answer briefly with small understanding ex.

thanks.

[Former Member]

hiii

Primary key is only one in any TABLE and it is created automatically.whatever key we create is a secondary key.

It is actually used to access data fastly.In live system there will be so much data.To find any one record from them is very difficult.So we use keys to access it fastly.go through following link also.

http://help.sap.com/saphelp_nw70/helpdata/en/cf/21ea77446011d189700000e8322d00/content.htm

reward if useful

thx

twinkal

Edited by: twinkal patel on Jun 20, 2008 11:17 AM

[Former Member]

Hi,

PRIMARY KEY:

Primary key is mandatory.

It avoids the duplicate entries of data and it should be a unique.

when you create the foreign key table . you want to refer only the primary key field of the reference table(checked table)

You can create no of primary keys for a table.

Regards.

[Former Member]

Hi,

Each SAP DB table has a primary key. The primary key is either defined by the database user or generated internally. A user-defined primary key can consist of multiple columns.

The primary index is distinguished from the secondary indexes of a table. The primary index contains the key fields of the table and a pointer to the non-key fields of the table. The primary index is created automatically when the table is created in the database.

You can specify the primary key for your container-managed entity bean when you create the bean, or later when you develop the bean business logic.

The beanu2019s primary key can be a:

· Simple primary key u2013 consists of one persistent field

· Compound primary key u2013 consists of several persistent fields

· Unknown primary key u2013 the primary key is unknown for the bean provider; at runtime the EJB Container generates automatically the values for that primary key.

Best regards,

raam

[Former Member]

Hi,

table key that is determined when you define a database table and which distinctively defines a table row. and it is unique.

To maintain records identically we use it.

you can define any number of primary keys in your table bbut that should have some usage like if take matnr in mara table that field connects several tables and even we can identify different materials using this.and by using it the retrival become faster

Regds,

Murali

[Former Member]

Hi Shirish,

Here is the below link go through all links

All are the concept Primiary key in data dictionary............

help.sap.com/saphelp_nw04/helpdata/en/41/7af4c5a79e11d1950f0000e82de14a/content.htm

www.informit.com/articles/article.aspx?p=425384&seqNum=3

ezinearticles.com/?Relational-Database-Management-System-in-SAP&id=320003

&********Reward Point if helpful***********&

[Former Member]

Hi,

Primary key mean in database table it avoid duplecate values and null values ,the field which u mentioned as primary key in a table it has only unique valu that purpus we use primary key in table.

with out primary key u can't create a teble.

max primary key in a table there is no number for that how many u want u can put that many in a table.

[Former Member]

Hi,

Generally a primary key in a database table is used to identify a row (record) uniqely in a database table. for any field if we dont want to allow duplicate values we can declare that field as a primary key.

For any table there can be only one primary key.

primary key are

simple primary key : generally it applies to a single field of a table.

compound primary key : we can put a combination of fields into a primary key. But we cant define multiple primary keys upon a single DB table. If we want more than one field to be in a primary key, we should use one comoound key with all those fields.

Thank you

Regards

Srinivas

[Former Member]

hi primary key is nothing but an unique key....its automatically created in the table.....using primary key we can fastly access the data from the data base.

exp:

student details:

roll no : is primary key(it is must)