What is difference b/w composit key n primary key and
forigion key?
Answer Posted / saraswathi muthuraman
Compost key :
More than one column will be used to create compst key
SQL> create table ts_250 (a number,b number,c number,
primary key(a,c));
Table created.
here column A and column C is used to create compst key.
U can't insert null value in both columns.
Only unique combination of column A and column B value can
be inserted.
Primary key :
Key will be created on a single column in table.
SQL> create table ts_251 (a number,b number,c number,
primary key(a));
Table created.
null value cann't be inserted into column a.
oracle will create a index
only unique value can be inserted into column a.
only one primary key can be created on a table
| Is This Answer Correct ? | 1 Yes | 0 No |
Post New Answer View All Answers
What is mysql default database?
Can you rename a database in mysql?
How to Recover a MySQL root password. Stop the MySQL server process. Start again with no grant tables. Login to MySQL as root. Set new password. Exit MySQL and restart MySQL server.
What is the use of mysqli_fetch_array?
Write command to import an mysql file?
How do you select a table?
What is user in mysql?
What is the password of mysql?
What command is used to delete the data from the table without deleting the table structure?
Write a query to retrieve a hundred books starting from 20th.
How do I find the size of a mysql database?
Is mysql query case sensitive?
how to add a new column to an existing table?
What are the difference between mongodb and mysql?
What are the column comparisons operators?