Question

1. If you were building a database table that contains the following attributes/fields: date, social security number, and phone number fields, how would you define each field (char, text or numeric, et.) and why?

2) Explain how and when it is appropriate to use the following SQL clauses/statements:
   a. GROUP BY vs. ORDER BY
   b. WHERE vs. HAVING

Answer 1

date = date

social security number = varchar2

phone = number

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GROUP BY VS ORDER BY

Group By : This will summarize unique combination of column values.

Order by : This is used to sort and display the data based on the specified columns.

See here it is displaying the product table data based on the column name in sorting order(ascending order by default) .

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Where vs Having:

Where : this is used to display the data based on the condition specified in the where clause.The Difference between where and having is , we cannot use "where" clause on the aggregates by we can use "having" on aggregates.

In general we have to use "where" before "group by" but we have to use "Having" after "group by".Thats why we call "where" as a pre-filter and "Having" as a post filter.

_____________________Thank You