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Explain why a primary key is a field which uniquely identifies the record?
Wiki User
∙ 14y ago
A database table will, under normal circumstances, have more than one column. So, assuming that there is a table of say, employees in a company, the table could look like First_name
Last_name
Date_of_Birth
The columns above could be duplicated if there are employees ...
Bill,Sykes,12 April 1977
Bill,Cody, 13 April 1977
Fred,Cody,14 April 1977
Fred,Sykes,15 April,1977
Henry,Smith,12 April 1977
As can be seen above First_name is duplicated with Bill and Fred - no good for a unique primary key. The same applies to Cody/Sykes and 12 April 1977.
At this point, it would be a good idea to bring in another column, say Employee_number, where each employee has a unique payroll number. This could be the unique primary key, only occurring once in the table.
It is possible to have a unique key spanning multiple columns, but that will bring extra overheads with indexing.
Wiki User
∙ 14y ago
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What are the advantage of primary key?
Primary key that is used to identify a record uniquely. Primary key is a key that always unique and not null. A system generated primary key is called surrogate key.Primary key is the one which is always unique and not null. Advantage of primary key that it helps in identifying a tuple uniquely.
What field makes the best primary key?
The field or combination of fields, the latter is called a composite key, which uniquely identifies a record. Often people use an integer automatically assigned at record creation, however, if possible it is best, to try for a field which is a unique attribute of the entity a table is describing.
What is a primary key what is its purpose and why do you use it?
A primary key is a unique identifier for each record in a database table. Its purpose is to ensure the uniqueness and integrity of the data within the table. It is used to uniquely identify each row, which allows for efficient data retrieval and modification, as well as establishing relationships between tables through foreign keys.
What is a primary key in relational databases?
A primary key is a set of one or more attributes that can uniquely identify tuples within the relation.A Primary Key is made up of one or more fields or columns that are used to uniquely identify a record or row in a table. No two records can have the same primary key and the database manager will not allow that to happenPrimary key consists of column or columns whose value uniquely identifies a row.Following are the key feature of primary keyIt can't be nullThere can ONLY be one primary key defined on a single table.A database designer choose this key to identifying unique records within a table. its values must not change. a primary key tells you the difference between James smith and another James smith because one has a different number than the other.The primary key is the field, or combination of fields, that uniquely identify each record in a table. It is usually the primary key that is stored in other tables (in which case it is called a "foreign key"), to find the record in the specified table. For example, a client might be identified by a field ClientId, which uniquely identifies each client. In the client table, this field would be called the "primary key"; if used in other tables to refer to a client, it is called a "foreign key".We can uniquely identify the database by which attribute or set of attributes that is called the PRIMARY KEY.it's basically a unique reference or ID (usually a number). You may need to create this in your database, or your dataset may already contain a unique ID field.In a database , the primary key field defines the field that is unique and not null. Primary key is used to uniquely define a key.It is used to uniquely identify each row in a table. The values must be unique and can not simply have NOT NULL.To uniquely identify a tuple or row in database , primary key must be used. a primary key is used to uniquely identify a tuple.A primary key is the unique identifier for a row in a database table. It is formed into a unique index constraint, so that access to the row in question can be quick. It is usually preferred by the optimizer as the primary join predicate. Presence of the primary key is usually a prerequiste for building a dynaset query, as opposed to a snapshot query, or for making an updateable view joining more than one table.the powerful in a releation database management system such as MICROSOFT ACCESS from the ability to quikly find and bring together information stored in separate tables. in order for MICROSOFT ACCESS to work most efficiently each table in your database should include a field or set of fields that uniquely identifies each individual record stored in table. this often a unique idnetification number,such as an employee ID number or serial number. IN DATABASE TERMINOLOGY, this information is called of the table. MICROSOFT ACCESS uses primary key field to quikly associate data from multiple tables and bring the data together for you. make sure the values in this field will always be different for each record MICROSOFT ACCESS doesnt allow duplicate values in
What is used to uniquely identify a record in a database program?
index field
The field that uniquely identifies a record in a table is called?
The field that uniquely identifies a record in a table is called the primary key. It ensures that each record in a table is distinct and can be easily located and referenced.
In a database a field that uniquely identifies a particular record in a table is called?
In a database, a field that uniquely identifies a particular record in a table is called
What is the field that uniquely identifies each record in a table?
Primary key is the field that uniquely identifies each record in a table. It ensures that each record in a table is unique, and helps to establish relationships between tables in a database.
What is A field that uniquely identifies a particular record in a table called?
A field that uniquely identifies a particular record in a table is called a primary key. The field or fields on which records are sorted is called the sort key.
What a field that uniquely identifies each field?
A primary key is a field that uniquely identifies each record in a database table. It must have a unique value for each record and cannot have null values. This key is essential for enforcing data integrity and for efficiently retrieving and updating records.
What does the primary key in a data base do?
We know that primary key is the one that is not null and is always unique. A primary key uniquely identifies a record in a table.
How do you uniquely identfied the record?
we will use primary key to uniquely idetified the record.
The foreign key uniquely identifies a record in a table T or F?
False. A foreign key is a primary of one table that is in another table. A foreign key can be repeated, so it does not uniquely identify records in the table where it is a foreign key.
Why is a field with an AutoNumber data type a good candidate for the primary key field for that table?
Because it uniquely identifies each record in that table, No two records can have the exact same entry in the field designated as the primary key.
Differentiate between primary secondary and foreign keys?
Primary key uniquely identifies each record in a database table and must have a unique value for each record. Secondary key is a field that can be used to uniquely identify a record, but it is not the primary key. Foreign key is a field in a table that links to the primary key of another table, establishing a relationship between the two tables.
What is a primary key of one file that appears in another file?
A primary key is one that uniquely identifies a record . Also there are cases when primary key of one file appears in another file. In that case the key is called Foreign key.
Can a primary key field uniquely identify each record?
Yes it can do that.
