AND, OR, NOT logical operators in MySQL - Step-by-Step Execution

Concept Flow - AND, OR, NOT logical operators

Start with condition1

↓

Evaluate condition2

↓

Apply AND operator

↓

Apply OR operator

↓

Apply NOT operator

↓

Result: TRUE or FALSE

↓

Use result to filter rows

Logical operators combine or modify conditions to filter database rows based on TRUE or FALSE results.

Execution Sample

MySQL

SELECT * FROM employees
WHERE (department = 'Sales' AND salary > 50000)
OR NOT (active = 1);

This query selects employees who are in Sales with salary over 50000, or who are not active.

Execution Table

Step	Condition Evaluated	Value 1	Value 2	Operator	Result
1	department = 'Sales'	Sales	-	-	TRUE
2	salary > 50000	60000	-	-	TRUE
3	TRUE AND TRUE	TRUE	TRUE	AND	TRUE
4	active = 1	0	-	-	FALSE
5	NOT FALSE	FALSE	-	NOT	TRUE
6	TRUE OR TRUE	TRUE	TRUE	OR	TRUE
7	Row included in result	-	-	-	YES

💡 All conditions evaluated; final result TRUE means row is included.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	Final
department = 'Sales'	unknown	TRUE	TRUE	TRUE	TRUE	TRUE	TRUE	TRUE
salary > 50000	unknown	unknown	TRUE	TRUE	TRUE	TRUE	TRUE	TRUE
active = 1	unknown	unknown	unknown	unknown	FALSE	FALSE	FALSE	FALSE
AND result	unknown	unknown	unknown	TRUE	TRUE	TRUE	TRUE	TRUE
NOT result	unknown	unknown	unknown	unknown	unknown	TRUE	TRUE	TRUE
OR result	unknown	unknown	unknown	unknown	unknown	unknown	TRUE	TRUE

Key Moments - 3 Insights

Why does the NOT operator change FALSE to TRUE in step 5?

NOT reverses the condition result. Since active = 1 is FALSE (active is 0), NOT FALSE becomes TRUE as shown in step 5.

Why is the AND operator result TRUE in step 3?

AND returns TRUE only if both conditions are TRUE. department = 'Sales' and salary > 50000 are both TRUE, so AND result is TRUE in step 3.

How does the OR operator affect the final result in step 6?

OR returns TRUE if either side is TRUE. Here, AND result is TRUE and NOT result is TRUE, so OR result is TRUE, including the row.

Visual Quiz - 3 Questions

Look at the execution table, what is the result of 'salary > 50000' at step 2?

A TRUE

B FALSE

C UNKNOWN

D NULL

💡 Hint

Check the 'Value 1' column at step 2 showing salary 60000 > 50000.

At which step does the NOT operator change the condition result?

A Step 4

B Step 5

C Step 3

D Step 6

💡 Hint

Look for the step where 'NOT' is listed as the operator.

If 'active' was 1 instead of 0, what would be the OR result at step 6?

A UNKNOWN

B FALSE

C TRUE

D NULL

💡 Hint

If active=1, then active=1 condition is TRUE, NOT TRUE is FALSE, but AND result is TRUE, so OR TRUE OR FALSE is TRUE.

Concept Snapshot

AND, OR, NOT combine conditions in SQL WHERE clauses.
AND requires both conditions TRUE.
OR requires at least one TRUE.
NOT reverses TRUE/FALSE.
Used to filter rows based on multiple criteria.

Full Transcript

This visual execution shows how SQL logical operators AND, OR, and NOT work step-by-step. We start by evaluating simple conditions like department = 'Sales' and salary > 50000. Then AND combines these two conditions, returning TRUE only if both are TRUE. Next, we evaluate active = 1, which is FALSE in this example. The NOT operator reverses this FALSE to TRUE. Finally, OR combines the AND result and the NOT result. Since both are TRUE, the OR result is TRUE, so the row is included in the query result. The variable tracker shows how each condition's value changes at each step. Key moments clarify common confusions about how NOT reverses values and how AND and OR combine conditions. The quiz tests understanding of these steps by asking about specific condition results and operator effects.