SELECT Queries

Question 1

Which clause is used to specify the table from which data is retrieved in a SQL query?

A.

A) SELECT

B.

B) FROM

**Explanation:** FROM identifies the table(s), such as Employees, containing the data to query.

C.

C) WHERE

D.

D) ORDER BY

Question 2

Why must the FROM clause always execute before the WHERE clause in SQL?

A.

A) Because WHERE needs access to the table data that FROM retrieves

**Explanation:** The FROM clause identifies and retrieves the source table(s). WHERE cannot filter rows without first having a dataset to filter from, so FROM must execute first logically and physically.

B.

B) Because the database optimizer requires it

C.

C) Because SELECT cannot work without FROM first

D.

D) Because it improves query performance

Question 3

If a query has both WHERE and HAVING filtering different conditions, in what order do they execute?

A.

A) HAVING first, then WHERE

B.

B) WHERE first, then HAVING

**Explanation:** WHERE executes after FROM but before GROUP BY and HAVING. This order ensures that only relevant rows are grouped, and then aggregate-based filtering via HAVING is applied to the groups.

C.

C) Simultaneously

D.

D) The order depends on the database system

Question 4

A database administrator asks you to retrieve all project information from the Projects table to verify the data exists. Which query should you use?

A.

A) SELECT * FROM Projects;

Explanation: SELECT * FROM Projects returns all columns (ProjectID, ProjectName, DeptID) for every project. The SHOW command is not appropriate for data retrieval, and selecting individual columns would omit important information.

B.

B) SELECT ProjectName FROM Projects;

C.

C) SELECT ProjectID FROM Projects;

D.

D) SHOW * FROM Projects;

Question 5

What is the purpose of replacing * with specific column names in a SELECT statement?

A.

A) To sort the results alphabetically

B.

B) To limit output to only desired fields from the table

Explanation: Specifying column names after SELECT limits the output to those fields, reducing unnecessary data retrieval.

C.

C) To create a new table

D.

D) To filter rows based on conditions

📝 SELECT Queries - 1

Quiz Complete!