Question

Kindly assist in the solution to these problems.

2a) Give an example of when a view might be helpful. Give an example of when a view might be required for purposes of confidentiality and security.

b) In an explicit LEFT JOIN, the first table mentioned after the FROM keyword should be the table whose rows you want to include in the results even if the other table does not have a corresponding value for the field that’s being joined on. (True or False?)

c) In an explicit LEFT JOIN, all desired fields mentioned in the SELECT clause must appear on the left-hand side of the query results, before (i.e., to the left of) any fields (columns) from the other table. (True or False?)

c) In SQLplus, if you run an SQL query file using “@myScript”, can the script contain more than one SQL statement?

d) Oracle and SQLplus are generally case-insensitive regarding SQL keywords and column names, but Linux is case-sensitive regarding file names.

e) Nested queries (subqueries) must be enclosed in parentheses.

f) What, if anything, is wrong with the following SQL query? (This may be followed by any of a zillion possible made-up query examples.)

g) Regarding NULL values: Is the result of TRUE OR UNKNOWN True, False, or Unknown?

h) Can a primary key be null? Why or why not?

Answer 1

a) view is useful for security as from entire table we want to shoe particular columns only and hide the other columns from the user.

for example in employee table we want to display only name and address and hide salary column; view can be created.

b)true

c)false...(question is not very clear)

d)true

e)true

f)no query mentioned

g)unknown

h)no, primary key cant be null because of entity integrity rule