Define candidate key, alternate key, composite key?
Answer Posted / jeff
A candidate key is able to identify a unique tuple in a
relation through an attribute or attribute set.
A foreign key makes sure that a tuple in a relation does
not match a tuple in another relation which does not exist
| Is This Answer Correct ? | 46 Yes | 58 No |
Post New Answer View All Answers
Explain about network model?
Explain the role of indexing in databases?
Why does this query return 0?
State the acid rules?
You are testing the performance of a query the first time you run the query, the performance is slow. the second time you run the query, the performance is fast. why is this?
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 xml databases?
There is a trigger defined for INSERT operations on a table, in an OLTP system. The trigger is written to instantiate a COM object and pass the newly insterted rows to it for some custom processing. What do you think of this implementation? Can this be implemented better?
What are the key features of dbms?
Pgm A calls Pgm B and pgm B uses cursor, when pgm B is called second time, the program is abending saying the cursor is opened? Why?
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?
How to use timestamp datatypes
What is the database development process?
Explain about normal forms?
Explain about relational operator join?