what are the joins,primary key,foriegn key, candidate key, super key and expai

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what are the joins,primary key,foriegn key, candidate key,
super key and expain them?

Question Posted / jawahar

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what are the joins,primary key,foriegn key, candidate key, super key and expain them?..

Answer / monal

Joins: Joins are used to retrieve data from two or more
tables when there is either matching row exist in another
table or not.

Primary Key: Primary key ensures uniqueness of data in a
table so that no two rows in the table can have same value.

Foreign Key: Foreign key ensures that data entered in a
column must be checked with data already entered in the
primary key column of another table.

Candidate Key: In some tables there is possibility that more
than one column can carry unique values to make sure
uniqueness of data all across the table. one of those key
column becomes Primary key and other column become candidate
key.

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what are the joins,primary key,foriegn key, candidate key, super key and expain them?..

Answer / hari

Joins are retrive the data multiple tabels
primary key ;-doesn' allow null vales

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what are the joins,primary key,foriegn key, candidate key, super key and expain them?..

Answer / jebastin unnatha raja

Joins-> Joins allow You to view and retrive the data from multible related tables in a single result set.

Primary key-> A primary key is used to uniquely identify each row in a table.A primary key columns can not contain a nULL values.

foriegn key-> A foreign key is a field (or fields) that points to the primary key of another table. The purpose of the foreign key is to ensure referential integrity of the data

super Key-> A superkey is a combination of attributes that can be uniquely used to identify a database record. A table might have many superkeys.

Candidate key-> A candidate key is one that can identify each row of a table uniquely. Generally a candidate key becomes the primary key of the table.

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what are the joins,primary key,foriegn key, candidate key, super key and expain them?..

Answer / karthik

Join is a keyword which is used to join two or more table.

The unique column in a table is called primary key.

If primary key acting as a normal attribute in some other
table then this attribute is called foreign key.

If table is having more than one unique attribute then the
rest of the attributes of primary key is called candidate key.

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what are the joins,primary key,foriegn key, candidate key, super key and expain them?..

Answer / vikash kr pandey

1> JOIN:- JOIN IS USED TO VIEW AND RETRIEVE DATA FROM MULTIPLE TABLE OR RELATED TABLES IN A SINGLE RESULT SET.

2> PRIMARY KEY:-PRIMARY KEY IS A SET OF COLUMNS WHOSE VALUES UNIQUELY IDENTIFY ALL THE ROWS IN A TABLE AND CAN NOT CONTAIN NULL VALUES.

3> FORIEGN KEY:-A COLUMN IN ONE TABLE WHOSE VALUES MATCH THE PRIMARY KEY IN SOME OTHER TABLE IS CALLED A FORIEGN KEY.

4> CANDIDATE KEY:-ANY ATTRIBUTE THAT IS UNIQUELY IDENTIFIES A ROW IN A TABLE IS A CANDIDATE FOR THE PRIMARY KEY. THIS TYPE OF ATTRIBUTE IS CALLED CANDIDATE KEY.

5> SUPER KEY:-THE SUPERTYPE IS DESCRIBED BY ATTRIBUTES THAT BELONGS TO ALL SUBTYPES AND CONNECTED TO THE RELATIONSHIP WITH A LINE CONTAINING A CROSSBAR.

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what are the joins,primary key,foriegn key, candidate key, super key and expain them?..

Answer / navanirose

i want in super key sample queries and alternate key sample
queries .......pls send to imm.............

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