Answer / naz

A Candidate Key can be any column or a combination of
columns that can qualify as unique key in database. There
can be multiple Candidate Keys in one table. Each Candidate
Key can qualify as Primary Key.

A primary key is the column that uniquely identifies a
record. A primary key should be UNIQUE and never be NULL.

Answer / uday shankar dokku

candidate key: when we reduce unnecessary columns from a
super key it is called as candidate key
primary key: primary key is a constraint, in a table
there is only one primary key,a primary key is simple or
composite, a simple primary key is based on one column which
can be specified either inline outline of the constraint,a
composite primary key is based on (2-32)columns which can
be specified only out line of the constraint,a primary dose
not allows duplicates.

Answer / parijatha

there is no difference between the candidate and primary key
as both derives all other attributes in the relation.The
concept of primary key came into account to make the search
easy the is whenever a candidate key is declared as primary
key the primary key attribute gets sorted which reduces the
response time

How do we select distinct values from a table?

0 Answers  

---

1.If we have a Salary coloumn in Staff entity with this description the salary must be monetary and >=$35450.00, how we can write it in into schemain SQL? 2. If we have Weight and Marks in Assessment entity and the Weight has the description of this it must be Non-zero percentage. And also the Marks attribute stores the maximum possible raw mark for assessment (e.g., 30), while Weight stores of the weight of this assessment for the paper as a whole (e.g., 10%). If Marks is not specified, then Weight is used for both. How we can convert this into schema in SQL????

0 Answers  

---

What do you understand by b-trees?

0 Answers  

---

What's the difference between star and snow flake schema?

0 Answers  

---

There are 100 datafiles, numbered from 1 to 100. File number 10 is deleted and it has 500 MB of data. The database is working in archive log mode. How can be the database recovered ? While doing recovery the archive logs applied are from nos 1 to 100, but 50 gets corrupted. What do we do? Can we proceed further? If so how?

0 Answers  

---

Explain the necessary techniques to control deadlocks?

0 Answers  

---

Explain 2nf?

0 Answers  

---

What is the Result of the following 'VIK'||NULL||'RAM' ?

1 Answers   HP, Manthan Solutions,

---

What is normal form in dbms?

0 Answers  

---

Explain what are called fat clients and fat servers?

0 Answers  

---

What is the use of FULL option in EXP command ?

1 Answers  

---

How to retrive a single data from a database

0 Answers   MCN Solutions,

---