# Bar Charts from SQL Data
Bar charts are useful for comparing values between categories.
In this tutorial, the number of security events at each risk level will be displayed as a bar chart.
---
## Step 1 - Create the SQL Query
```sql
SELECT
risk_level,
COUNT(*) AS total
FROM cyber_security_events
GROUP BY risk_level;
```
Example result:
| risk_level | total |
|------------|------:|
| Low | 15 |
| Medium | 8 |
| High | 3 |
---
## Step 2 - Retrieve the Data with PHP
```php
query($sql);
$data = [];
while($row = $result->fetch())
{
$data[] = [
$row['risk_level'],
(int)$row['total']
];
}
?>
```
---
## Step 3 - Create the Chart Container
```html
```
---
## Step 4 - Create the Bar Chart
```html
```
[](https://mr.napper.au/uploads/images/gallery/2026-06/image-1782085906217.png)
## Changing the Chart Type
Only one line of code needs to change.
Pie Chart:
```javascript
new google.visualization.PieChart()
```
Bar Chart:
```javascript
new google.visualization.BarChart()
```
Column Chart:
```javascript
new google.visualization.ColumnChart()
```
Line Chart:
```javascript
new google.visualization.LineChart()
```
---
## Complete Example
```php
query($sql);
$data = [];
while($row = $result->fetch())
{
$data[] = [
$row['risk_level'],
(int)$row['total']
];
}
?>
```
---
## Next Tutorial
**Line Charts from SQL Data**
Learn how to display trends and changes over time using a line chart.