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What is table, field, record, null in rdbms?

What is Table?

The data in RDBMS is stored in database objects called tables. The table is a collection of related data entries and it consists of columns and rows.

  • Remember, a table is the most common and simplest form of data storage in a relational

database.  Following is the example of a STUDENT table:

table

 

 

What is Field?

  • Every table is broken up into smaller entities called fields. The fields in the  STUDENT table consist of s_id, s_name, s_age.
  • A field is a column in a table that is designed to maintain specific information about every record in the table.

What is Record or Row?

  • A record, also called a row of data, is each individual entry that exists in a table.
  • For example there are 4 records in the above  STUDENT table. Following is a singlerow of data or record in the STUDENT table:

record

 

Record is a Horizontal Entity in a table

What is Column?

A column is a vertical entity in a table that contains all information associated with a specific field in a table.

  • For example, a column in the  STUDENT  table is s_name

column

 

 

What is NULL value?

  • A NULL value in a table is a value in a field that appears to be blank which means a field with a NULL value is a field with no value.
  • It is very important to understand that a NULL value is different than a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank During record creation.

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