Correct Answer: PL/SQL tables are scalar arrays that can be referenced by a binary digit They can be used to store values for later queries and calculations
4. Difference between a query and a statement in SQL?
Correct Answer: An SQL statement is a string of characters that conforms to the syntax and format specified in the international standard A query is a statement that returns a record-set
5. Write an SQL Query to find employees whose name starts with an ?M??
Correct Answer: Similarity: Both WHERE and HAVING Clause filters out records based on one or more conditions Difference: WHERE Clause can only be applied to a static non-aggregated column whereas HAVING is needed for aggregated columns
8. What are defaults? Is there a column to which a default can?t be bound?
Correct Answer: A default is a value which will be used by a column, if no value is supplied to that column while inserting data Yes, IDENTITY and TIMESTAMP columns are free from the bounds of default
9. What are constraints? Mention the different types of constraints?
Correct Answer: Constraints enable the RDBMS to enforce the integrity of the database automatically, without the need to create triggers, rule or defaults Types of Constraints: NOT NULL, CHEQUE, UNIQUE, PRIMARY KEY, FOREIGN KEY
10. What is the difference between a primary key and a unique key?