What is difference b/w composit key n primary key and
forigion key?
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Answer / sathish
Assume a table contains columns
book name
author name
price
>>composite key
Having multi column primary key for a single table is known as composite key.
ex: primary composite key is book name and author name
>>primary Key
Primary key is the unique key, do not accept null value and used as a id to fetch the record from the table.
>> Foreign Key
A primary key of a table which is used as a reference key of another table..
Is This Answer Correct ? | 16 Yes | 0 No |
Answer / 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 ? | 5 Yes | 0 No |
Answer / 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 |
Answer / reem
A primary key is a column which uniquely identifies the
records in a table.
A foreign key is a column (the child collumn) in a table
which has a corresponding relationship and a dependency on
another collumn (the parent collumn) that is usually in a
different table.
comosit key is more than one attribute can used as aprimary
key
Is This Answer Correct ? | 1 Yes | 0 No |
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