Constraints in SQL

What does the ALTER TABLE clause do?

• The SQL ALTER TABLE clause modifies a table definition by altering, adding, or deleting table columns and/or constraints

• The SQL ALTER TABLE clause is used to insert data into database table

• THE SQL ALTER TABLE deletes data from database table

• The SQL ALTER TABLE clause is used to delete a database table

Correct syntax query syntax to drop a column from a table is

• DELETE COLUMN column_name;

• DROP COLUMN column_name;

• ALTER TABLE table_name DROP COLUMN column_name;

• None is correct.

SQL has how many main commands for DDL:

• 1

• 2

• 3

• 4

Which command is used for removing a table and all its data from the database:

• Create command

• Drop table command

• Alter table command

• All of the mentioned

Which of the following language is used to specify database Schema ?

• DDL

• DML

• DCL

• None

With SQL, how can you insert a new record into the "Persons" table?

• INSERT INTO Persons VALUES ('Jimmy', 'Jackson')  
• INSERT ('Jimmy', 'Jackson') INTO Persons
• INSERT VALUES ('Jimmy', 'Jackson') INTO Persons
• INSERT VALUES ('Jimmy, Jackson') INTO Persons
• INSERT ('Jimmy', 'Jackson') VALUES into Persons

Which of the following is NOT a type of SQL constraint?

• Primary Key

• Foreign Key

• Alternate Key

• Unique

• NOT NULL

______________ constraint prevents NULL values

• UNIQUE

• NOT NULL

• NULL

• FOREIGN KEY

Correct syntax query syntax to drop a column from a table is

• DELETE COLUMN column_name;

• DROP COLUMN column_name;

• ALTER TABLE table_name DROP COLUMN column_name;

• None is correct.

The primary key of a table which is present in another table for referencing is known as ________________________