QA

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Sams Teach Yourself SQL in 24 Hours, Third Edition
By Ronald R. Plew, Ryan K. Stephens
Table of Contents
Hour 2.  Defining Data Structures


Q&A

Q1:

How is it that I can enter numbers such as a person's Social Security number in fields defined as character fields?

A1:

Numeric values are still alphanumeric , which are allowed in character data types. Typically, the only data stored as numeric values are values used in computations . However, it may be helpful for some to define all numeric fields with a numeric data type to help control the data entered in that field.

Q2:

I still do not understand the difference between constant-length and varying-length data types. Can you explain?

A2:

Say you have an individual's last name defined as a constant data type with a length of 20 bytes. Suppose the individual's name is Smith. When the data is inserted into the table, 20 bytes are taken, 5 for the name and 15 for the extra spaces (remember that this is a constant-length data type). If you use a varying-length data type with a length of 20 and inserted Smith, only 5 bytes of space are taken.

Q3:

Are there limits on the lengths of data types?

A3:

Yes, there are limits on the lengths of data types and they do vary among the various implementations .


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Sams Teach Yourself SQL in 24 Hours
Sams Teach Yourself SQL in 24 Hours (5th Edition) (Sams Teach Yourself -- Hours)
ISBN: 0672335417
EAN: 2147483647
Year: 2002
Pages: 275

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