what is the difference between primary key & foreign key?
Answers were Sorted based on User's Feedback
Answer / vij&pani
Primary key is unique key but foriegn key always refers to
primary key
Is This Answer Correct ? | 327 Yes | 50 No |
Answer / ramprakash
Primary keys enforce entity integrity by uniquely
identifying entity instances. Foreign keys enforce
referential integrity by completing an association between
two entities.
Is This Answer Correct ? | 275 Yes | 50 No |
Answer / guest
Primary key is unique
primary key is not NULL and
foreign key is NULL
foreign key reference as Primary key in another table
Is This Answer Correct ? | 250 Yes | 62 No |
Answer / guest
primary key is used to identify a row and it doesnot allow
null values. It avoids duplication of rows.
whereas foreign key refers to a column or combination of
columns included in the defenition of referential integrity.
Is This Answer Correct ? | 155 Yes | 19 No |
Answer / muneer
Primary Key is unique Key entire the table and which is
also NOT NULL
where as foriegn key is the null & which references the
primary key .
Is This Answer Correct ? | 147 Yes | 28 No |
Answer / shaik gouse peer
Basic difference betweeen Primary key and foreign key is :
Primary key will not allow "Null values" and "Duplicate
values"
Foreign key will allow "Null values" and "Duplicte values"
and it refers to a primary key in anoter table.
Is This Answer Correct ? | 130 Yes | 25 No |
Answer / guest
primary key is the parent and foreign is the child.
Is This Answer Correct ? | 132 Yes | 73 No |
Answer / hardik patel
primary key is used to identify a row and it doesnot allow
null values. It avoids duplication of rows.
whereas foreign key refers to a column or combination of
columns included in the defenition of referential integrity.
Is This Answer Correct ? | 65 Yes | 20 No |
Answer / gaurav , ashish ,preeti , main
Primary key is used to identify a row in a table and it
doesnot allow null values. It avoids duplication of rows.
whereas foreign key refers to a column or combination of
columns included in the defenition of referential integrity
Is This Answer Correct ? | 57 Yes | 16 No |
Answer / raghu
In the context of relational databases, a foreign key is a
referential constraint between two tables.[1] The foreign
key identifies a column or a set of columns in one
(referencing) table that refers to a column or set of
columns in another (referenced) table. The columns in the
referencing table must form a primary key or unique key.
Is This Answer Correct ? | 58 Yes | 20 No |
What do you mean by group by clause?
Is primary key = unique key,not null? If yes,please explain IF No,please explain
What is a system tablespace and when it is created?
How to define an oracle cursor variable?
1. How actually index will work ? 2. Why do people prefer mostly bitmap index and btree index in datawarehouse ? 3. If I use the column in aggrigate functions like max,min,count and avg and if I have a index created on that column, will it increases the performance ?
How to get execution path reports on query statements?
Differentiate between pre-select and pre-query?
How to connect to the server with user account: sys?
What is the usage of synonyms?
can you write commit in triggers?
How would you extract DDL of a table without using a GUI tool?
What is the difference between postgresql and oracle?