Every sequence number has been defined 1 generated by user, In between tables, usage of multiple sequence number may get overlapped and may lose the uniqueness in some of the table, For Example, in this application we have created four tables and all the tables has got unique column as record-id, On some occasions, cycle of sequence may produce may hardness, Hence, if one has decided to use unique sequence as record identifier instead of linking between tables, there is another functions called sys-guid() can be used in place of sequence, SYS-GUID() generates and returns a globally unique identifier made up to 16 BYTES but the data type is RAW and need to be converted in terms of number to use in our record-id,
The syntax of usage sys-guid() is as follows:
To-Number ( SYS-GUID( ),
'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX')
In this context, we have come across a new word as "Primary Key" which is nothing but identifying a record with a unique key value, This will be discussed at the time of creation of database constraint,