DDL Quiz - Languages SQL

Free practice quiz: DDL (Languages SQL). 52 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This Languages SQL practice quiz has 52 multiple-choice questions on DDL, and 52 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. Which SQL statement is used to modify existing records in a table?

   1. ALTER TABLE
   2. MODIFY RECORD
   3. UPDATE
   4. CHANGE RECORD
   Show answer

   Answer: C. UPDATE

   The UPDATE statement is used to modify existing records in a table. ALTER TABLE is used to modify the table structure. MODIFY RECORD and CHANGE RECORD are not standard SQL commands for this purpose.

2. What is the purpose of a `CONSTRAINT` in SQL DDL?

   1. To define the order of rows in a table
   2. To enforce rules on the data in a table
   3. To create indexes for faster querying
   4. To define relationships between tables
   Show answer

   Answer: B. To enforce rules on the data in a table

   Constraints are DDL elements used to enforce data integrity and business rules. Examples include `PRIMARY KEY`, `UNIQUE`, `FOREIGN KEY`, `NOT NULL`, and `CHECK` constraints.

3. What does the `NOT NULL` constraint enforce in SQL?

   1. That a column must contain a unique value
   2. That a column cannot have a NULL value
   3. That a column must contain a value from a predefined list
   4. That a column cannot be modified
   Show answer

   Answer: B. That a column cannot have a NULL value

   The `NOT NULL` constraint ensures that a column cannot contain `NULL` values. Every row must have a value in such a column.

4. Which DDL statement is used to create a new user-defined function (UDF)?

   1. CREATE PROCEDURE
   2. CREATE UDF
   3. CREATE FUNCTION
   4. CREATE ROUTINE
   Show answer

   Answer: C. CREATE FUNCTION

   `CREATE FUNCTION` is the DDL statement used to define and create user-defined functions, which are stored procedures that return a single value.

5. Which SQL data type is best suited for storing boolean values (TRUE/FALSE)?

   1. INT
   2. VARCHAR
   3. BOOLEAN
   4. DECIMAL
   Show answer

   Answer: C. BOOLEAN

   The `BOOLEAN` data type is specifically designed to store logical values, typically represented as TRUE or FALSE. Some SQL dialects might use `BIT` or other representations.

More questions in this quiz

Answers and explanations are in the full quiz.

1. Which of the following is NOT a valid DDL statement in SQL?
2. What is the primary purpose of a `CREATE TABLE` statement in SQL?
3. Which SQL keyword is used to remove a table from the database?
4. What does the `ALTER TABLE` statement allow you to do?
5. Consider the following SQL statement: `CREATE TABLE Employees (EmployeeID INT PRIMARY KEY, FirstName VARCHAR(50), LastName VARCHAR(50));` What does `PRIMARY KEY` signify in this context?
6. Which DDL command is used to create an index on one or more columns of a table to speed up data retrieval?
7. What is the difference between `DROP TABLE` and `TRUNCATE TABLE`?
8. Which of the following is a valid data type for storing a date in SQL?
9. When adding a `FOREIGN KEY` constraint, what must the referenced column in the other table have?
10. Which SQL statement is used to add a new column to an existing table?
11. What does `VARCHAR(n)` typically represent in SQL data types?
12. Which statement is used to create a database view?
13. Which of the following is a DDL statement used to modify the structure of a table by renaming it?
14. When defining a `CHECK` constraint, what is its purpose?
15. What is the SQL keyword used to create a new database?
16. Which DDL statement allows you to define the structure for a new schema within a database?
17. What is the purpose of a `UNIQUE` constraint in SQL?
18. Which of the following SQL data types is most suitable for storing a large text document?
19. Which SQL statement is used to create a new user account in a database system?
20. What is the effect of executing `ALTER TABLE Customers DROP COLUMN Email;`?
21. Which DDL command is used to create a stored procedure?
22. What is the data type `DECIMAL(p, s)` used for in SQL?
23. When using `ALTER TABLE` to add a constraint, what is the typical syntax for adding a `FOREIGN KEY`?
24. What is the primary function of a `PRIMARY KEY` constraint on a table?
25. Which SQL DDL statement is used to create a database trigger?
26. What is the main difference between `CREATE TABLE` and `CREATE VIEW`?
27. Consider `ALTER TABLE Products ADD CONSTRAINT PK_ProductID PRIMARY KEY (ProductID);`. What does this statement accomplish?
28. What is the purpose of a `DEFAULT` constraint in SQL?
29. What is the SQL data type `FLOAT` typically used for?
30. Which of the following SQL statements modifies the data type of an existing column?
31. What is the purpose of the `CASCADE` option when defining a `FOREIGN KEY` constraint with `ON DELETE` or `ON UPDATE`?
32. Which SQL DDL command is used to create a schema that groups related database objects?
33. What does `IDENTITY` or `AUTO_INCREMENT` typically signify when used with a column definition in SQL?
34. Which SQL statement is used to remove a database from the system?
35. What is the purpose of the `REPLACE` keyword in some SQL `CREATE` statements (e.g., `CREATE OR REPLACE VIEW`)?
36. Which SQL statement can be used to add a `CHECK` constraint to an existing column?
37. What is the primary purpose of the `FOREIGN KEY` constraint?
38. What does the `ON DELETE SET NULL` clause do when defining a `FOREIGN KEY` constraint?
39. Which DDL statement is used to create a unique index on a table?
40. What is the purpose of a `TRUNCATE TABLE` statement?
41. Which SQL statement is used to create a new database user with specific privileges?
42. What is the function of the `REFERENCES` clause when defining a `FOREIGN KEY` constraint?
43. Which of the following is a DDL statement for defining a new table with specific columns and data types?
44. What is the purpose of the `ON DELETE RESTRICT` or `ON DELETE NO ACTION` clause for a `FOREIGN KEY` constraint?
45. When altering a table, what does `ALTER TABLE ... ALTER COLUMN column_name SET NOT NULL;` achieve?
46. Which DDL statement is used to create a new database role?
47. What is the purpose of the `COMMENT ON` statement in SQL?

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