# Unpivot
`Unpivot` is a powerful tool to convert table columns into rows. Specifically, it transforms multiple columns into two columns: `unpivot_table_metric` and `unpitvot_table_value` . Column names are placed in the former columns and their corresponding values are in the latter column. Notice that `Unpivot` is not the exact reverse of the [Pivot Table](/acho-studio/data-prep-projects/applying-actions.md#16-pivot-table) action, since it doesn't do any aggregation or produce a summary table. That is, `Unpivot` doesn't merge several values into one value. It merely changes the format of a table by transforming a wide table into a long table.
Below is an example table that shows how often people wear masks in two counties of New York during COVID-19. `Never`, `rarely`, `sometimes`, `frequently`, and `always` refers to the proportion of the population in different levels of mask-wearing frequency. We can combine them together by applying the `Unpivot` action, so the table becomes a longer table with fewer columns (from 7 columns to 4 columns).
## How to apply Unpivot?
There are two options under `Unpivot` in Acho:
* **Columns to unpivot**
You can click the dropdown menu to choose one or more columns to unpivot.
* **Columns to keep**
For the rest of the columns that are not used for unpivoting, you can decide whether to keep them or not. This option is optional. You can specify 0 or more columns to keep.
## **Data types for unpivoted columns**
1. If unpivoted columns are all in the same type, the `unpivot_table_value`column will have the same data type. Take the mask-wearing data as an example. Since all input columns are in a float type, the type of the resulting column is also Float.
2. If unpivoted columns have mixing types (such as integer and string), the `unpivot_table_value`column will result in a string type. Below is an example to unpivot columns that have mixing types(integer, string, and date).
## **When to use Unpivot?**
1. When you have multiple columns that share the same characteristics (for example, `never`, `rarely`, `sometimes`, `frequently`, and `always` refers to the frequency of mask-wearing), you want to combine them together.
2. When you have multiple columns that indicate distinct metrics (such as the number of confirmed cases and deaths of COVID-19), you want to create a line chart or column chart to compare these metrics at the same time.
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