primary key and unique key
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.
Related Tutorials/Questions & Answers:
primary key and unique key
primary key and unique key hello, What's the difference between a primary key and a unique key? hii,ADS_TO_REPLACE_1 Unique key.... Primary key: columns entry of duplicate as well as null values are restricted
primary key and unique key hello, What's the difference between a primary key and a unique key? hii,ADS_TO_REPLACE_1 Unique key.... Primary key: columns entry of duplicate as well as null values are restricted
Advertisements
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.ADS_TO_REPLACE_1 Both primary 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.ADS_TO_REPLACE_1 Both primary key
What is a "primary key"?
What is a "primary key"? What is a "primary key"? Hi, Here is the answer,ADS_TO_REPLACE_1 A primary key is used to uniquely identify...). A primary key can consist of one or more fields on a table. When multiple fields
What is a "primary key"? What is a "primary key"? Hi, Here is the answer,ADS_TO_REPLACE_1 A primary key is used to uniquely identify...). A primary key can consist of one or more fields on a table. When multiple fields
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
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
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
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
SQL Auto increment Primary Key
SQL Auto increment Primary Key SQL Auto increment Primary Key is used to allow a unique... from 'SQL Auto increment Primary Key'. To understand this example we use a query
SQL Auto increment Primary Key SQL Auto increment Primary Key is used to allow a unique... from 'SQL Auto increment Primary Key'. To understand this example we use a query
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. ADS_TO_REPLACE_1
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. ADS_TO_REPLACE_1
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
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_TableADS_TO_REPLACE_1 SQL
SQL Alter Table Primary Key Alter a Table Primary Key in SQL modifies the existing table and adds a primary key. Create Table Stu_TableADS_TO_REPLACE_1 SQL
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
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
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
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
SQL PRIMARY KEY Constraint
a unique values. It should contain NULL values. The Table contain a primary key... SQL PRIMARY KEY Constraint The PRIMARY KEY constraint is used to uniquely
a unique values. It should contain NULL values. The Table contain a primary key... SQL PRIMARY KEY Constraint The PRIMARY KEY constraint is used to uniquely
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
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 this tutorial illustrate an example from 'Mysql Add Primary Key'. To understand
Mysql add primary key Mysql add Primary Key is used to add primary key on the column... of this tutorial illustrate an example from 'Mysql Add Primary Key'. To understand
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
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
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
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
How to create primary key using hibernate? Hi, How to create primary key using hibernate? Thanks
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
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 Unique Key
Mysql Alter Unique Key ... unique key on specified column of a table.It allows one NULL value... Unique Key'. The example create a table 'employee' with required fieldnames
Mysql Alter Unique Key ... unique key on specified column of a table.It allows one NULL value... Unique Key'. The example create a table 'employee' with required fieldnames
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
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
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
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
ModuleNotFoundError: No module named 'django-uuid-primary-key'
ModuleNotFoundError: No module named 'django-uuid-primary-key' Hi...: No module named 'django-uuid-primary-key' How to remove the ModuleNotFoundError: No module named 'django-uuid-primary-key' error? Thanks
ModuleNotFoundError: No module named 'django-uuid-primary-key' Hi...: No module named 'django-uuid-primary-key' How to remove the ModuleNotFoundError: No module named 'django-uuid-primary-key' error? 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 ExampleADS
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 ExampleADS
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
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
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
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_TableADS_TO_REPLACE_1 SQL
SQL Alter Table Primary Key Alter a Table Primary Key in SQL modifies the existing table and adds a primary key. Create Table Stu_TableADS_TO_REPLACE_1 SQL
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
can we update table in hibernate with out primary key in table? can we update table in hibernate with out primary key in table
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
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
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
query regarding auto increment primary key i want to use s1,s2.... as my auto increment primary key.cant i do this in mysql
PHP Array Unique Key
PHP Array Unique Key In PHP if we want to get all the keys then we can use array_keys() function. array_keys() function returns an array of all keys..., present in the array. PHP Unique Array Key Example 1: <?php
PHP Array Unique Key In PHP if we want to get all the keys then we can use array_keys() function. array_keys() function returns an array of all keys..., present in the array. PHP Unique Array Key Example 1: <?php
Define candidate key, alternate key, composite key.
Define candidate key, alternate key, composite key. Define candidate key, alternate key, composite key
Define candidate key, alternate key, composite key. Define candidate key, alternate key, composite key
Mysql Alter Foreign Key
Mysql Alter Foreign Key A Foreign Key is a field that marks to the primary key...` varchar(50) NOT NULL, `contact_name` varchar(50) default NULL, PRIMARY KEY
Mysql Alter Foreign Key A Foreign Key is a field that marks to the primary key...` varchar(50) NOT NULL, `contact_name` varchar(50) default NULL, PRIMARY 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
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
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..._TO_REPLACE_1 Pen Tool: Take "cccccc" color and choose Pen tool (P key), Make
How to design key It has been made easy now to design a key by this example, just..._TO_REPLACE_1 Pen Tool: Take "cccccc" color and choose Pen tool (P key), Make
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
), 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
(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
Automatic key press
Automatic key press Hi Please any one help me is it possible automatic key press in j2me
Automatic key press Hi Please any one help me is it possible automatic key press in j2me
ModuleNotFoundError: No module named 'key'
ModuleNotFoundError: No module named 'key' Hi, My Python program is throwing following error: ModuleNotFoundError: No module named 'key' How to remove the ModuleNotFoundError: No module named 'key' error
ModuleNotFoundError: No module named 'key' Hi, My Python program is throwing following error: ModuleNotFoundError: No module named 'key' How to remove the ModuleNotFoundError: No module named 'key' error
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
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
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
java key value pair
java key value pair Hi, How to save the java key value pair in Java? Thanks Hi, You can use the Hashtable for this purpose. Check the tutorial Creating a Hash Table. Thanks
java key value pair Hi, How to save the java key value pair in Java? Thanks Hi, You can use the Hashtable for this purpose. Check the tutorial Creating a Hash Table. Thanks
how to use foreign key in java
, first name varchar(10), primary key(id) ) CREATE TABLE table2 ( id_fk int, last... CASCADE ) The point is that table2 has a foreign key referencing the primary key...how to use foreign key in java I have two tables in my MySQL
, first name varchar(10), primary key(id) ) CREATE TABLE table2 ( id_fk int, last... CASCADE ) The point is that table2 has a foreign key referencing the primary key...how to use foreign key in java I have two tables in my MySQL
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
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
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
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
what is key in kafka?
what is key in kafka? Hi, I was searching for Big Data jobs on internet and almost all the Big Data Job recruiters are asking for Kafka skills. what is key in kafka? How to learn Kafka? Thanks Hi, Yes in most
what is key in kafka? Hi, I was searching for Big Data jobs on internet and almost all the Big Data Job recruiters are asking for Kafka skills. what is key in kafka? How to learn Kafka? Thanks Hi, Yes in most
Ads