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 the datatype of image?
What are the 5 r's of managing behaviors?
How to display odd rows in student table in mysql?
I've looked but can't find a MySQL equivalent for MS SQL's xp_cmdshell. I have 7z files that I want to unzip and load into MySQL. I'm trying to write a sp to do the unzip, but I can't find a way to do that. Can anyone provide an example of a similar process in Windows? TIA.
Is mysql an oracle product?
What is mysql installer?
How to decrement dates by 1 in mysql?
Does mysql automatically index foreign keys?
What are mysql functions?
What is the difference between BLOB AND TEXT?
Write a query to fetch common records between two tables using mysql?
What is the data type for image?
How do I restore a mysql database dump file in linux?
How do I create a mysql database?
How to create table with same structure of student table in mysql?