A Guide to SQL
A Guide to SQL
9th Edition
ISBN: 9781111527273
Author: Philip J. Pratt
Publisher: Course Technology Ptr
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Chapter 6, Problem 12CAT
Program Plan Intro

Primary key:

  • To identify each record in a table, at least there must be one data field, which should be unique.
    • That is corresponding data field of every record should be unique.
    • It is called primary key.
  • Primary key is used to identify the unique record from a collection of records.

“VARCHAR” datatype:

  • The “VARCHAR” datatype will hold a variable length string which contain numbers, special characters and letters.
  • The maximum size is specified in parenthesis. The “VARCHAR” datatype can store up to 255 characters.

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