primary key and unique key

Home Answers Viewqa JDBC primary key and unique key

QuestionAsk Questions?

Clark

primary key and unique key
1 Answer(s) 2 years and 8 months ago
Posted in : JDBC

Whats is mean by primary key and unique key?

View Answers

November 12, 2010 at 5:55 PM

Hi friends,

Primary Key:- Primary Key is an attribute or a set of attributes in a table which uniquely identifies a record (row) in a table and no two records (rows) in the table can have the same values for all the columns comprising the primary key.

Unique Key:- A unique key is a key which stores unique values (no duplicates) for that particular column.

Difference between Primary Key & Unique Key:-

A Unique key can store a null value and primary key cannot store any null value.
A primary key can be references to another table as a Foreign Key.

Thanks.

primary key and unique key
primary key and unique key Whats is mean by primary key and unique key

primary key and unique key
primary key and unique key hello, What's the difference between a primary key and a unique key? hii, Unique key: column restricts entry of duplicate values but entry of null values is allowed. Primary key

difference between a primary key and a unique key?
difference between a primary key and a unique key? What's the difference between a primary key and a unique key? Hi, The column holding... the unique constraint can accept null values. Both primary key and unique

SQL PRIMARY KEY Constraint
SQL PRIMARY KEY Constraint The PRIMARY KEY constraint is used to uniquely identifies each record in a database table. The Primary keys in a table contains a unique

Mysql Alter Unique Key
Mysql Alter Unique Key ... The Tutorial illustrate an example from 'Mysql Alter Unique Key'. The example.... The table has a ID as Primary Key. Create table "employee":

SQL Auto increment Primary Key
SQL Auto increment Primary Key SQL Auto increment Primary Key is used to allow a unique... increment Primary Key'. To understand this example we use a query 'use

What is a "primary key"?
What is a "primary key"? What is a "primary key"? Hi, Here is the answer, A primary key is used to uniquely identify each row... be an artificial field (one that has nothing to do with the actual record). A primary key can

composinte primary key in hibernate
composinte primary key in hibernate I am facing following problem, Inside the database(mssql), i have created a table without primary key... primary key with all the columns of the table and hibernate s/w has created two pojo

Create primary key using hibernate
Create primary key using hibernate How to create primary key using hibernate? The id element describes the primary key for the persistent class and how the key value is generated. <id name="id

Adding A Primary Key to an Existing Table
Adding A Primary Key to an Existing Table Been trying to add a primary key to a MySQL table using Java for two days with no success. I'm new... KEY (SerialNo)"); out.println("Primary key added

SQL Alter Table Primary Key
SQL Alter Table Primary Key Alter a Table Primary Key in SQL modifies the existing table and adds a primary key. Create Table Stu_Table SQL statement to create

Hibernate unique key validation example
Hibernate unique key validation example Hi, How to preform unique key validation in Hibernate application? Thanks Hi, You write a program to check for the presence of the key in database before performing add

changing primary key of parent table
changing primary key of parent table I want to change one primary key from a table where primary key is auto created? How can I do that? I have tried UPDATE person SET personid=3494 WHERE personid=8483; and i get the following

JDBC insert that returns primary key
JDBC insert that returns primary key How to write code for jdbc insert that returns primary key? Help me fast Thanks Hi, Following code can be used: //Add record into database String queryInsert = "insert

Mysql add primary key
Mysql add primary key Mysql add Primary Key is used to add primary key on the column of existing... illustrate an example from 'Mysql Add Primary Key'. To understand and grasp

SQL Primary Key
SQL Primary Key The Primary Key in SQL is used to uniquely identifies each records in a database table. The Primary Key of the Table does not include NULL values. In SQL

hibernate annotations with composite primary key
to use hibernate annotations in case of composite primary key in one table. I tried like this, I have created a table without primary key. By default mssql has created a composite primary key with all the columns of the table. table

how tohow to create a table with primary key and foreign keyhow to create a table with primary key and foreign key
how tohow to create a table with primary key and foreign keyhow to create a table with primary key and foreign key how to create a table using java language with primary key and foreign key Hi Friend, A foreign

Mysql Alter Table Primary Key
Mysql Alter Table Primary Key Mysql Alter Table Primary Key is used to remove the primary key from the table and add primary key to the existing other column of table

Difference between not null and primary key in mysql
Difference between not null and primary key in mysql Explain not null and primary key in mysql

How to create primary key using hibernate?
How to create primary key using hibernate? Hi, How to create primary key using hibernate? Thanks

Mysql Alter Column Primary Key
Mysql Alter Column Primary Key Mysql Alter Column Primary Key is used to modify table and redefine the Primary Key Column in a table. Understand with Example The Tutorial

How to auto increment primary key in mysql...
How to auto increment primary key in mysql... How to auto increment primary key in mysql... and one more thing i need to get auto increment value in front end each time for inserting the value[JSP

Define sequence generated primary key in hibernate
Define sequence generated primary key in hibernate How to define sequence generated primary key in hibernate? Use value "sequence" for class attribute for generator tag. <id column="USER_ID" name="id" type

query regarding auto increment primary key
query regarding auto increment primary key i want to use s1,s2.... as my auto increment primary key.cant i do this in mysql

SQL Alter Table Primary Key tutorial
SQL Alter Table Primary Key Alter a Table Primary Key in SQL modifies the existing table and adds a primary key. Create Table Stu_Table SQL statement to create

inserting into mysql database with uid to be primary key and autoincrement
inserting into mysql database with uid to be primary key and autoincrement hello, i am new to jsp and facing problem in creating a database entry.... In the database table, set the uid as the primary key and auto-increment. Then, whenever

can we update table in hibernate with out primary key in table?
can we update table in hibernate with out primary key in table? can we update table in hibernate with out primary key in table

Mysql Alter Foreign Key
Mysql Alter Foreign Key A Foreign Key is a field that marks to the primary key..., `contact_name` varchar(50) default NULL, PRIMARY KEY (`publisher_id

PHP Array Unique Key
PHP Array Unique Key In PHP if we want to get all the keys then we can use.... PHP Unique Array Key Example 1: <?php $array...; General Description of array_key General Format

foreign key error in sql
), stadium varchar2(10),city varchar2(10),mom varchar2(10),primary key(mid,mdate... varchar2(10),sixes varchar2(10),primary key(mid.pid), foreign key(mid...foreign key error in sql create table matchdetails(mid varchar2(10

hibernate Foreign key
(255) DEFAULT NULL, City varchar(255) DEFAULT NULL, PRIMARY KEY (P_Id...) NOT NULL, OrderNo int(11) NOT NULL, P_Id int(11) DEFAULT NULL, PRIMARY KEY (O_Id), KEY P_Id (P_Id), CONSTRAINT orders_ibfk_1 FOREIGN KEY (P_Id) REFERENCES

Define candidate key, alternate key, composite key.
Define candidate key, alternate key, composite key. Define candidate key, alternate key, composite key

Identify correct and incorrect statements or examples about an entity bean's primary key and object identity.
an entity bean's primary key and object identity. Prev Chapter 8... and incorrect statements or examples about an entity bean's primary key and object... of an entity object on the basis of its PRIMARY KEY

Make Unique Column in Database Table
a unique key in a column of a database table. While declaring unique key... a unique column. After assigning the unique key to a column the SQL statement... Make Unique Column in Database Table

How to design key, design key, key
How to design key It has been made easy now to design a key by this example, just...: Take "cccccc" color and choose Pen tool (P key), Make points. Select

Mysql Alter Command
TABLE tablename DROP PRIMARY KEY; For removing a Unique index... key','Unique index','Delete Column','Change column' etc. Understand with Example... primary key is used to remove/delete the primary key in a table.

java.sql.BatchUpdateException: Duplicate entry '135-16448' for key 1 - Hibernate
or it should be primary key that it should be already in the database ... ServerPreparedStatement.java:647 there is duplicate key in your Query or it should be primary...java.sql.BatchUpdateException: Duplicate entry '135-16448' for key 1

Automatic primary Generation in Hibernate - Hibernate
Automatic primary Generation in Hibernate Hi, Ow primary key is generated automatically in hibernate.give me sample code.Thank u

Automatic key press
Automatic key press Hi Please any one help me is it possible automatic key press in j2me

php array sort by key
php array sort by key php script to sort array by key

uikeyboard disable return key
uikeyboard disable return key uikeyboard - hot to disable return key

KEY EVENT HANDLING
KEY EVENT HANDLING I am trying to write a program that receives every key stroke even when the window is not active or it's minimized. Is there anyway to do

Foreign key update table
Foreign key update table How to update table that has the foreign key in SQL..? ALTER TABLE YourTable ADD CONSTRAINT FK_YourForeignKey FOREIGN KEY (YourForeignKeyColumn) REFERENCES YourPrimaryTable

registration key - Java Beginners
registration key I want the serial key for JCreator Pro 4.50. I lost it. If any body has it please send

Foreign key in mysql
Foreign key in mysql Hi I am creating a website and linking it to a database using php and mysql. I need to create the databases in phpmyadmin... the foreign key of one table into another table within phpmyadmin so the database

Key requirement for business analyst
Key requirement for business analyst What are the key requirement of the business analyst? A Business analyst plays a key role... of the key requirements for business analyst are mentioned below: Good

Understanding Hibernate <generator> element
generates the primary key for new record. There are many options provided...; element is used to specify the class name to be used to generate the primary key...; In this case <generator> element do not generate the primary key

ordering the data on a selected key

Latest
Frameworks
Category