Informatics Practices
What is the purpose of DROP TABLE command in MySql ? How is it different from DELETE command ?
Answer
The DROP TABLE command in MySql is used to permanently delete an entire table from the database, including its structure, data, indexes, triggers, and constraints. The DELETE command, on the other hand, is used to remove specific rows or all rows from a table, leaving the table structure intact.
Related Questions
Mr. Mittal is using a table with following columns :
Name, Class, Stream_Id, Stream_nameHe needs to display names of students who have not been assigned any stream or have been assigned stream_name that ends with "computers".
He wrote the following command, which did not give the desired result.
SELECT Name, Class FROM Students WHERE Stream_name = NULL OR Stream_name = "%computers" ;Help Mr. Mittal to run the query by removing the error and write correct query.
The Doc_name Column of a table Hospital is given below :
Doc_name Avinash Hariharan Vinayak Deepak Sanjeev Based on the information, find the output of the following queries :
(i) SELECT docname FROM HOSPITAL WHERE Docname like "%v";
(ii) SELECT docname FROM HOSPITAL WHERE docname like "%e%";
Sarthak, a student of class XII, created a table "Class". Grade is one of the columns of this table. To find the details of students whose Grades have not been entered, he wrote the following MySql query, which did not give the desired result:
SELECT * FROM Class WHERE Grade = "Null";Help Sarthak to run the query by removing the errors from the query and write the correct query.
What is the purpose of ALTER TABLE command ? Can you add new columns with constraints such as NOT NULL ? Give example to justify your answer.