Interested to Buy Any Domain ? << Click Here >> for more details...
What is the main different between Null and NOT Null.
Difference between Primary and Unique Key.
How to Check the database from which application is it
possibe.
- 6 Answers
- 8707 Views
- I also Faced
- E-Mail Answers
Answers were Sorted based on User's Feedback
Answer / kalpana
Primary key can never be NULL.it is used to uniquely
identify the row in a table.The database engine requeir a
value to relocate the record.so Primary key can never be
NUL.unique key may be NULL.
| Is This Answer Correct ? | 21 Yes | 0 No |
Answer / sunil kumar
Hello Nivedita,
I am not satisfied with ur answer the difference between
primary key and foreign key.I think the answer is reverse.
| Is This Answer Correct ? | 15 Yes | 1 No |
Answer / bharanikumar
primary key does not allow null value,
but unique allow only one null value...
www.happylife.in
| Is This Answer Correct ? | 6 Yes | 0 No |
Answer / amit kumar tiwari
primary key uniquely define each table and never allow NULL
value. But unique key may be NULL value.
| Is This Answer Correct ? | 2 Yes | 1 No |
Answer / g priya
If a field is null the database engine makes the field to be 0
if not null is specified ,field must be given a value
Primary key is unique,not null,index where as Unique key has
1 null value
| Is This Answer Correct ? | 2 Yes | 5 No |
Answer / nivedita
IF NULL is specified,the feild is allow to be left empty
without any value.
IF NOT NULL is specified,the field must be given a value. In
the absence of either a NULL or NOT NULL, NULL is assumed.
-------
Unique key can't be NULL.Primary key can be NULL.
Unique key always contain unique value,duplicate are not
allowed(genrally the system genrated key).Primary key maybe
repeated.
| Is This Answer Correct ? | 6 Yes | 35 No |
How to run a sql statement?
Can you shard mysql?
Why is mysql used?
What do you mean by % and _ in the LIKE statement?
For the database from the previous question, please give an SQL query which returns the invoice number of all invoices which contain the article with the number ?1234?. The query should be able to run under a MySQL 4.0 database.
How you can create a trigger in mysql?
What are enums used for in mysql?
How do you determine the location of mysql data directory?
Does mysql use tcp or udp?
How can you retrieve a portion of any column value by using a select query?
How do I disable mysql?
Difference between MYSQL_ASSOC,MYSQL_NUM and MYSQL_BOTH ?
-
Oracle (3259) - SQL Server (4518)
- MS Access (429)
- MySQL (1402)
- Postgre (483)
- Sybase (267)
- DB Architecture (141)
- DB Administration (291)
- DB Development (113)
- SQL PLSQL (3330)
- MongoDB (502)
- IBM Informix (50)
- Neo4j (82)
- InfluxDB (0)
- Apache CouchDB (44)
- Firebird (5)
- Database Management (1411)
- Databases AllOther (288)
