Define candidate key, alternate key, composite key?
Answer Posted / manumole
Candidate key:
Candidate keys for a table includes the set of columns
which satisfies the criteria of a primary key.
Primary key : a column/combination of columns which
uniquely identifies a row and whose values are not null.
Clustered Key:when a combination of columns becomes a
primary key it is called as clustered key.
Alternate keys:the set of columns which is avialble in the
candidate keys and are not selected as primary key.
Eg:Customer table
candidate keys:{ CustomerID, MobNo(defined as not null) }
primary key: if Db designer selected as CustomerID,then
Alternate key is MobNo
Clustered key:if both combination CustomerID- MobNo is
taken as primary key,it is nothing but a clustered key
| Is This Answer Correct ? | 24 Yes | 22 No |
Post New Answer View All Answers
How long can an error message be in raiseerror function?
You have a table with three columns: amount1, amount2, and amount3 in a single row only one of these three columns will have a value and the other two will be null. Write a sql query to retrieve the values from these columns?
I HAVE A PI ON COL A THE NEXT DAY I WANT CHANGE THE PI ON COL B? PLS SEND ME THE ANS
explain detail about ftp in datastage?
Explain the role of indexing in databases?
What is the database development process?
Which four data types cannot be used as a return type from a user-defined function?
Who are end users in dbms?
How to use online Backups?
The count() function always returns a int value type what should you do if you need to count rows from a query which you know will return a value that is too large for an int value type?
Explain about relational operator join?
State the acid rules?
How to generate OIDS
How to combine two function together?
What is an application role and explain a scenario when you would use one?