Explain how to limit the rows that are retrieved by a query.
The number of rows returned by a select query can be restricted by the LIMIT clause.
Example:
SELECT * from employee
LIMIT 20
Explain how to sort the rows that are retrieved by a query.
Rows that are returned by a query can be sorted using the ORDER BY clause. By default the rows are sorted in an ascending order.
Example:
Select * from employee ORDER BY id DESC
What are the comparison operators in oracle. List them with description
Comparison operators in oracle are used to compare data. Such operators are used in WHERE clause.
List of such operators:
1. = -> EQUAL TO
2. <> != -> Both means NOT EQUAL TO
3. < LESS THAN
4. > GREATER THAN
5. <= >= -> LESS THAN OR EQUAL TO, GREATER THAN OR EQUAL TO
6. ANY- compares one value with any value
Example:
Select * from employee
Where id >=1
PL/SQL has three logical operators: AND, OR, and NOT. Explain then by illustrating an example for each
AND- It is used for conjunction. This means that for a row to be selected all the specified conditions must be true.
Example:
Select * from employee Where id= 1 AND 2
NOT- Is logical negation. This means that for a row to be selected the specified condition must be false.
Example:
Select * from employee Where NOT id=1
OR- it is used for inclusion. This means for the row to be selected at least one of the conditions must be true.
Example:
Select * from employee Where id =1 OR 2
