# Stacking
Stacking refers to combing series values into a single value while retaining their name. It is useful when you want to compare values as part of a whole. Certain chart types support stacking, they are: line, area, column, bar and combo.
## Adding @stacks
Stacking is enabled for a chart by specifying the `@stacks` directive
```sql
-- @chart: column
-- @title: Stacking - Example column chart with stacking
-- @groups: Month, Channel
-- @subtitle: An example column chart that has a single stack
-- @formats: currency
-- @series: Sales
-- @stacks: Channel
SELECT
TRUNC(date_closed, 'MONTH') as Month,
Channel,
sum(amount) as Sales
FROM sales
GROUP BY TRUNC(date_closed, 'MONTH'), Channel
ORDER BY TRUNC(date_closed, 'MONTH') ASC;
```
## Stacking Examples
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