WHERE with OR operator in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the OR operator do in a SQL WHERE clause?

The OR operator allows you to filter rows that meet at least one of multiple conditions. If any condition separated by OR is true, the row is included in the result.

beginner

Write a simple SQL query using WHERE with OR to find employees in department 10 or department 20.

SELECT * FROM employees WHERE department_id = 10 OR department_id = 20;

beginner

Can you combine multiple OR conditions in a WHERE clause?

Yes, you can combine many OR conditions. For example: WHERE condition1 OR condition2 OR condition3. The row is included if any condition is true.

intermediate

How does SQL evaluate WHERE conditions with OR and AND together?

SQL evaluates AND before OR unless parentheses change the order. Use parentheses to group conditions clearly, e.g., WHERE (A OR B) AND C.

beginner

What happens if you use OR with conditions that never match any row?

If none of the OR conditions are true for a row, that row is excluded from the result. OR only includes rows where at least one condition is true.

Which SQL query finds rows where column A is 5 or column B is 10?

A SELECT * FROM table WHERE B = 10;

B SELECT * FROM table WHERE A = 5 AND B = 10;

C SELECT * FROM table WHERE A = 5;

D SELECT * FROM table WHERE A = 5 OR B = 10;

The OR operator includes rows where either A = 5 or B = 10 is true.

What does this query return? SELECT * FROM users WHERE age = 20 OR age = 30;

A Users who are exactly 20 or exactly 30 years old.

B Users who are between 20 and 30 years old.

C Users who are not 20 or 30 years old.

D Users who are both 20 and 30 years old.

OR checks if age is 20 or age is 30, so it returns users with either age.

How does SQL treat this condition? WHERE A = 1 OR B = 2 AND C = 3

A It treats AND before OR, so it's A=1 OR (B=2 AND C=3).

B It treats OR before AND, so it's (A=1 OR B=2) AND C=3.

C It treats all conditions equally and randomly.

D It causes a syntax error.

AND has higher precedence than OR, so it evaluates B=2 AND C=3 first.

Which is true about the OR operator in SQL WHERE clause?

A It returns rows where all conditions are true.

B It returns rows where at least one condition is true.

C It returns rows where no conditions are true.

D It returns rows only if conditions are false.

OR includes rows if any condition separated by OR is true.

What is the result of this query? SELECT * FROM products WHERE price < 10 OR price > 100;

A Products priced exactly 10 or 100.

B Products priced between 10 and 100.

C Products priced less than 10 or greater than 100.

D No products will be returned.

OR includes products with price less than 10 or greater than 100.

Explain how the OR operator works in a SQL WHERE clause and give a simple example.

Think about choosing between two or more options.

Describe how SQL evaluates WHERE conditions when both AND and OR operators are used together.

Remember the order of operations like in math.