Oracle Questions And Answers

Posted by Stephen thangaraj at 09:22

Oracle  Questions  And Answers



Q1. Explain the use of the WHERE clause.
A1. It directs SQL to extract data from rows where the value of the column is the same as the current value of the WHERE clause variable.


Q2. What technique is used to retrieve data from more than one table in a single SQL statement?
A2. The Join statement combines data from more that two tables



Q3. What is a foreign key?
A3. It identifies a related row in another table and establishes a logical relationship between rows in two tables.


Q4. What are the reasons for adding an index to a table ?
A4. To increase lookup performance. For a unique key to guarantee the uniqueness of the values for a column on a table.


Q5. What is a primary key on a table used for ?
A5. Guaranteeing the uniqueness of a column on a table.






Q6. What is the purpose of a view?
A6. Views can be used to join and display data from multiple tables and to limit the number of columns and/or rows that are selected and displayed.





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