Interested to Buy Any Domain ? << Click Here >> for more details...
what is primary key,unique key, foreign key? can u teach me
in simple language?
- 44 Answers
- 187600 Views
- Banking, CMC, CTS, HCL, Infosys, Keggfarms, SkyEss, Sunrise, TCS, Web Synergies, Wipro, I also Faced
- E-Mail Answers
Answer Posted / sandeep beniwal (master)
Primary key:- Primary key means main key. A primary key is
one which uniquely identifies of a table. Prrimay key does
not allow null values and duplicate values.
e.g:
empno empname status
10 dipender active
20 nisha inactive
30 vikas active
40 naveen active
Pimary key not like this:
10 dipender active
20 nisha inactive
30 vikas active
naveen active ........ (duplicate value)
Unique key:-A unique is one which uniquely identifies a row
of a table, but there is a difference like it will allow
only one duplicate values (In sql).
Both will function in a similar way but a slight difference
will be there. So, decalaring it as a primary key is the
best one.
foreign key:- a foreign key is one which will refer to a
primary key of another table and helps making link
e.g
employee_table user_table
empID empname status userID userID empname
10 dipender active 1 1 dipender
20 nisha inactive 2 2 nisha
30 vikas active 3 3 vikas
40 naveen active 4 4 naveen
In the above relation, userID is there in employee_table
which
is a primary key of user_table. that means, userID is
refering the user_table.
| Is This Answer Correct ? | 1 Yes | 2 No |
Post New Answer View All Answers
Differentiate between unique key and foreign key?
Explain transaction manager?
How many types of locks are present in a database?
What is the DIF format and when we will use in teradata
Explain buffer manager?
What is a database call?
What is the importance of database partitioning?
Explain about ur projets on teradata???
How to do Data size testing? Who does this testing (Developer or tester)?
i applied prompt on country when i run report it shows list of all countries but want it to show only four countries name
Design an ETL process( batch job/script)from source to starting that u will not be dependent on the source in the near future?please elobarate details on what are things to consider.if you'd like to do a diagram that will be great.please answer it
What is the difference between oracle and MS Access?
How to shrink a database?
What are different types of blocks used in stored procedure?
Under which circumstance should you create an index on a table?
