Answer Posted / madhumita majhi

In SQL both primary key and unique enforce uniqueness of
the column on which they are defined. But by default
primary key creates a clustered index on the column, where
are unique creates a non-clustered index by default.
Another major difference is that, primary key doesn't allow
NULLs, but unique key allows one NULL only.

Unique Key: Identify the row by uniquely, means if you are
inserting a records into the table suppose you already
inserted a record with ID 101 and another record you are
inserting with the same ID then it will give an error
(unique key voilation).

Prmary Key:Once you define a primay key on a particular
column then a column become a mandatory field.That means
you need to insert something on it, you can not leave as a
blank otherwise it will give an error as primary key
voilation.

What is Library Cache in Oracle?

1070

---

Are truncate and delete commands same? If so why?

1072

---

How do I learn what codesets are available in oracle?

996

---

What is meant by recursive hints in oracle?

1023

---

how can we store any pdf file in oracle

2093

---

What is tns service name?

1068

---

What are a query and state the different types of queries and their uses?

940

---

How would you best determine why your MVIEW couldnt FAST REFRESH?

1835

---

What is the use of aggregate functions in oracle?

978

---

Hi friends can u send the oracle 9i full version download link?????????????? please reply ?

1813

---

What happens if the imported table already exists?

970

---

Difference between the “verify” and “feedback” command?

1308

---

How to start a specific oracle instance?

987

---

How to select some columns from a table in oracle?

999

---

If any one has information regarding interview of NIC (National Informatics Centre),it would be of great help...

2183

---