Computer Science
Differentiate between the following statements:
(i) ALTER and UPDATE
(ii) DELETE and DROP
Answer
(i) Differences between ALTER and UPDATE statements:
ALTER statement | UPDATE statement |
---|---|
The ALTER statement is used to modify the structure of database objects, such as tables, views, or schemas. | The UPDATE statement is used to modify the existing data in a table. |
It can be used to add, modify, or drop columns, constraints, or indexes in a table. | It is used to change the values of one or more columns in a table based on specified conditions. |
For example: ALTER TABLE Employees ADD Email VARCHAR(255); | For example: UPDATE Employees SET Email = 'john.doe@example.com' WHERE EmployeeID = 101; |
(ii) Differences between DELETE and DROP statements:
DELETE statement | DROP statement |
---|---|
The DELETE statement is used to remove one or more rows from a table based on specified conditions. | The DROP statement is used to remove entire database objects, such as tables, views, indexes, or schemas, from the database. |
It deletes specific rows of data while keeping the table structure intact. | It deletes the entire object along with its structure and data. |
For example, DELETE FROM Employees WHERE Department = 'Marketing'; | For example, DROP TABLE Products; |
Related Questions
Site any two differences between Single Row Functions and Aggregate Functions.
What do you understand by Cartesian Product?
Write the name of the functions to perform the following operations:
- To display the day like 'Monday', 'Tuesday', from the date when India got independence.
- To display the specified number of characters from a particular position of the given string.
- To display the name of the month in which you were born.
- To display your name in capital letters.
Write the output produced by the following SQL statements:
(a)
SELECT POW(2, 3);
(b)
SELECT ROUND(342.9234, -1);
(c)
SELECT LENGTH("Informatics Practices");
(d)
SELECT YEAR("1979/11/26"), MONTH("1979/11/26"), DAY("1979/11/26"), MONTHNAME("1979/11/26");
(e)
SELECT LEFT("INDIA", 3), RIGHT("ComputerScience", 4), MID("Informatics", 3, 4), SUBSTR("Practices", 3);