Mysql

Question 1

CHAR datatype

Answer 1

1) fixed length
2) given length of the string less than given fixed length ->length = fixed length

Question 2

Add primary key to a relation

Answer 2

ALTER TABLE tablename ADD PRIMARY KEY

Question 2

Add an attribute to an existing table

Answer 2

ALTER TABLE table_name ADD attribute name DATATYPE;

Question 2

Modify datatype of an attribute

Answer 2

ALTER TABLE table_name MODIFY attribute DATATYPE

Question 3

Modify constraint of an attribute

Answer 3

ALTER TABLE table_name MODIFY attribute DATATYPE NOT NULL;

Question 4

Remove an attribute

Answer 4

ALTER TABLE table_name DROP attribute

Question 5

Remove primary key from the table

Answer 5

ALTER TABLE table_name DROP PRIMARY KEY;

Question 6

drop a table

Answer 6

DROP TABLE table_name;

Question 7

drop a database

Answer 7

DROP DATABASE database_name;

Question 8

Renaming of columns

Answer 8

SELECT EName as Name FROM EMPLOYEE;

Question 9

Distinct Clause

Answer 9

SELECT DISTINCT DeptId FROM EMPLOYEE;

Question 10

Data Updation

Answer 10

tax:
UPDATE table_name
SET attribute1 = value1, attribute2 = value2, …
WHERE condition;