Author Question: In the database redesign process, before proceeding with the redesign it is often useful to ... (Read 114 times)

AEWBW

  • Hero Member
  • *****
  • Posts: 579
In the database redesign process, before proceeding with the redesign it is often useful to ________.
 
  A) check whether certain conditions or assumptions about the data are valid
  B) find out why the design was not done properly the first time
  C) stop information systems and users from influencing each other
  D) set standards for user behavior

Question 2

Briefly describe subqueries and joins. Explain when each is not an acceptable alternative for the other.
 
  What will be an ideal response?



EAN94

  • Sr. Member
  • ****
  • Posts: 307
Answer to Question 1

A

Answer to Question 2

Subqueries and joins are both methods for retrieving data from multiple tables. Subqueries involve nesting one SELECT statement within another. The nested SELECT is used as part of a condition in the WHERE clause of the first SELECT statement. The nested SELECT statement can return a set of records from one table, which are then used in a logical operator within the parent SELECT query. A join combines records from each table into concatenated records containing the fields of both tables. The records are concatenated based on matching values in similar columns in the two tables. Subqueries cannot be used in situations where the results to be displayed include attributes from more than one table. Joins cannot be used as an alternative to a correlated subquery.



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
 

Did you know?

Certain chemicals, after ingestion, can be converted by the body into cyanide. Most of these chemicals have been removed from the market, but some old nail polish remover, solvents, and plastics manufacturing solutions can contain these substances.

Did you know?

Thyroid conditions may make getting pregnant impossible.

Did you know?

More than 150,000 Americans killed by cardiovascular disease are younger than the age of 65 years.

Did you know?

Blastomycosis is often misdiagnosed, resulting in tragic outcomes. It is caused by a fungus living in moist soil, in wooded areas of the United States and Canada. If inhaled, the fungus can cause mild breathing problems that may worsen and cause serious illness and even death.

Did you know?

Recent studies have shown that the number of medication errors increases in relation to the number of orders that are verified per pharmacist, per work shift.

For a complete list of videos, visit our video library