Explain the MySQL cursor statements. What will be an ideal ...

[codyclark]

Explain the MySQL cursor statements.
 
  What will be an ideal response?

Question 2

What is the multivalue, multicolumn problem, and why is it a problem? Include an example.
 
  What will be an ideal response?

[aburgess]

Answer to Question 1

The MySQL cursor statements include DECLARE CURSOR CursorName to define a cursor, OPEN CursorName to actually start the use of the cursor, and CLOSE CursorName to end the use of a cursor. While the cursor is running, the FETCH keyword is used to retrieve row data. A cursor is used with a looping structure of some sort, which can be created using the REPEAT and WHILE keywords.

Answer to Question 2

The multivalue, multicolumn problem occurs when a table uses multiple columns to store multiple values of an attribute. For example, a database of dog owners might have a table with the structure:

DOG_OWNER (OwnerID, LastName, FirstName, DogName01, DogName02, DogName03 )

This is a problem because (1 ) the number of DogNames is fixed, and (2 ) this structure creates query problems. In fact, this structure is another form of the multivalued dependency, and requires a similar solution: a DOG table should be created to store the DogNames and with a foreign key to link the dogs to their owner.