Appendix C. Using SQL Datatypes
As explained in Lesson 1, “Understanding SQL,” datatypes are essentially rules that define what data may be stored in a column and how that data is actually stored.
Datatypes are used for several reasons:
Datatypes enable you to restrict the type of data that can be stored in a column. For example, a numeric datatype column will only accept numeric values.
Datatypes allow for more efficient storage, internally. Numbers and date-time values can be stored in a more condensed format than text strings.
Datatypes allow ...
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