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Learn how to use Redash to query and display your database data

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# Learn Redash
Learn how to use [Redash](https://redash.io/) to query and display your data in
a dashboard.

## Why?
Technical team members can easily access a project's data writing SQL queries in
the command line however for non-technical team members this is not the case.
Having access to a project's data is valuable. It allows you to analyse and
evaluate users' behaviours in order to make informed decisions about what the
project needs going forward.

Dashboards are an appealing means of displaying a project's data in a
user-friendly way. Whilst you can custom make a dashboard for your project this
can be complex and time-consuming according to the needs of the client. Redash
is a pre-made dashboard tool that is easy to connect to your data and offers a
lot of inbuilt functionality to help solve these problems.

## What?

Redash is a paid for service that provides an online, up to date, queryable
dashboard of a project's data. Prices start from $29 a month with a free 30 day
trial, which is useful for those who may be using it as a stop-gap or want to
test the waters of whether it will truly benefit them. To follow the
instructions in this readme your project must be hosted on Heroku and using
PostgreSQL.

### Real world examples

- Building a new application and looking to gain a better understanding of
user's behaviours. Redash proved a helpful and more detailed layer to complement
Google Analytics and Tag Manager.
- A platform with different user types where admins need the ability to query
and search the data. Doing so will help the project management and give admins
a better understanding of how the app is being used.
- A client in need of a reporting tool. Rather than having to build a bevy of
reports (ranging from simple to complex) into the core of their application,
many of which would be used only by one client or as a one-off, they have chosen
to create these in Redash. They'll create dashboards for their clients and this
also reduces the client team's dependence on developers.

## How?

Your needs and interaction with Redash will vary according to your technical
proficiency:

- For basic view only access login and take a look either at your list of
dashboards or queries from the main menu. Can't see anything? Ask your technical
team to make sure they have 'published' the queries and dashboards they've
created which will make them visible to you.

- To learn how to write your own basic queries see
[learning SQL](#an-introduction-to-sql-for-writing-queries).
- As a developer looking to set up and configure Redash start by creating an
account in the next section.

### Create an account

To set up Redash on your project start by going to redash.io and entering in
basic details to create an account (name, email, org name, password). You will
be able to create accounts for other users at a later date but this number is
capped on the free version, so it may be advisable to set up the account using
a project email address if you have one.

### Add a data source

Having successfully created an account, next you need to connect your account
to a 'data source' ie. your project! To connect your data source you will need
to fill out the following page:

![image](https://user-images.githubusercontent.com/16775804/32285039-09508b56-bf21-11e7-9716-2961edc81ffb.png)

- If your page doesn't look like this to start, ensure your first option 'Type'
 has `PostgreSQL` selected.
- For the 'Name' value enter a name of your choice
- To fill in the remaining values you need to extract this data from your
`DATABASE_URL` config variable found on Heroku (under 'Settings' , 'Reveal
Config Vars'). The url is structured in the following way and you must dissect
the values for each of these things:

postgres:// **user** : **password** @ **host** : **port** / **name**

Once you've entered your user/password/host/port and name values in you're ready
to hit 'save' and your data source is now set up! You can click the 'Test
Connection' button just to be sure everything's working ok.

### Querying your data source

Next to display your data to your client you should set up a query. Queries
should be written in SQL to extract the information you desire. You should
establish the technical proficiency and level of control a client wishes to have
in order to decide what queries to write and who should be writing them. The
results / data from all Redash queries can be downloaded into excel files so as
a starting point you may wish to write a simple query to display the basic
values of each of your tables and then less technical users can explore this
data in excel which may be more familiar to them. Exploring data in downloaded
files is also lower risk because if you change/delete data using your queries on
Redash you will be editing your live data!

To set up a new query go to:
![image](https://user-images.githubusercontent.com/16775804/32285773-431b757e-bf23-11e7-93bf-66e64df68c1d.png)

And create a simple query such as `SELECT * FROM your-table-name;` to get all of
the data from a given table:
![image](https://user-images.githubusercontent.com/16775804/32285945-d414d534-bf23-11e7-9941-5fea73df9803.png)
Conveniently, Redash provides you with the schema of your db so you can look up
table and column names by exploring the box on the left hand side.

Once you've written your query click 'Execute' and then wait until the results
of your query are displayed below:

![image](https://user-images.githubusercontent.com/16775804/32286104-4d6d2210-bf24-11e7-9708-76c0bcbcfdad.png)

In this example, as our query asked for the entire table, this is what our
result shows. If you are happy with the query/results remember to click 'Save'
so you can return to your query in the future! You can also see the option to
download this content as a .csv or excel file on the right which is the option
you may wish to select if choosing to share your data with your client in this
way. If you want other team members to be able to see your query you should
'publish' it, then it will be visible to all users.

If you don't yet know SQL and want to know how to write more queries take a look
at the following section:

### An introduction to SQL for writing queries

:bangbang: NOTE: Any commands that use **the words UPDATE, DROP, ALTER, CREATE,
INSERT or DELETE will make permanent changes to your data**, do not use them
unless you have checked with your team that you are not using your site's live
data. :bangbang:

#### Select data from one table

A query is a request you make to your database for some information. The most
simple query you can run is one which displays data for you. So if your database
had a table called 'People' that looked like this:

**People**

| User ID | Name     | Age | Occupation      |
|---------|----------|-----|-----------------|
| 1       | Amy      | 29  | Violinist       |
| 2       | Bob      | 55  | Tree Surgeon    |
| 3       | Clarissa | 42  | Physiotherapist |

and you wanted to write a query that would display all of this data to you you
would write:

`SELECT * FROM people;`

In this command you are selecting all of the data (the asterisk represents all
  values) from your table called 'People'. All SQL commands must end with a
  semi-colon to indicate that this is the end of your query.

#### Select data from two tables

In order to display data from two tables together you can do an inner join. So
if I wanted to combine the values from the people table above with the pets
table:

| pet_id | pet_name | animal | owner_id |
|--------|----------|--------|----------|
| 9      | Fido     | Dog    | 1        |
| 10     | Tiddles  | Cat    | 1        |
| 11     | Spot     | Dog    | 2        |

You would write:

```
SELECT * FROM people
JOIN pets
ON people.user_id = pets.owner_id;
```

An inner join will combine rows from different tables if the join condition is
true. So joining the people and pets tables we would get a result like this:

| user_id | name | age | occupation   | pet_id | pet_name | animal | owner_id |
|---------|------|-----|--------------|--------|----------|--------|----------|
| 1       | Amy  | 29  | Violinist    | 9      | Fido     | Dog    | 1        |
| 1       | Amy  | 29  | Violinist    | 10     | Tiddles  | Cat    | 1        |
| 2       | Bob  | 55  | Tree Surgeon | 11     | Spot     | Dog    | 2        |

Notice how Amy appears twice because she has 2 pets whereas Clarissa no longer
appears as she has no pets.

#### Select one column of data

If you just want to see one column of data run the following command:

```
SELECT people.name
FROM people;
```

Which will give you:

| Name |
|------|
| Amy  |
| Amy  |
| Bob  |

#### Further Learning
If you've got time to learn a bit more about SQL why not try:
- The Codeacademy tutorial - https://www.codecademy.com/learn/learn-sql
- Or this one from Mode - https://community.modeanalytics.com/sql/tutorial/introduction-to-sql/

Here's a **glossary of terms** for those more familiar with SQL looking for a
reminder: https://www.codecademy.com/articles/sql-commands?r=master

### Setting up permissions for different users

Depending on which Redash package you are paying for you have the opportunity to
set up multiple users. You can put users into groups to determine what access
rights they should have either read only or full.

#### Choosing read only or full access
To amend the permissions of your users **start by going to** the settings page
which can be accessed via the **cog in the top right navbar**:

From here **select the Groups tab**:

![image](https://user-images.githubusercontent.com/16775804/34616777-19010984-f231-11e7-9bde-1bde42a88736.png)

Automatically all users are part of the 'Default' group. **Select or create the
group whose permissions you wish to set**. If you are creating a new group you
will need to select from the dropdown the users you wish to add to the group.

Then **select the data source** you wish to apply these permissions to (you may
  just have one):
![image](https://user-images.githubusercontent.com/16775804/34616900-7889d25a-f231-11e7-9dff-8d32ddef19bb.png)

Then select the permission level, you can **choose from either: full access or
read-only**:

#### Sharing data with external clients

In some instances you may wish to share data with someone who is external to
your company. Rather than setting up this user with an account you can either
download and share your data or send them a shareable link. Here's how:

##### Downloading data

To download a query, select the query in your queries list and then click:
<img src="https://user-images.githubusercontent.com/16775804/34619365-c62ff89c-f239-11e7-8f90-cf2ebabc5590.png" width=200px />

You also have this option when viewing queries in your dashboard:
<img src="https://user-images.githubusercontent.com/16775804/34619428-010ca5a0-f23a-11e7-83d1-cdf382f71df4.png" width=180px />

To download a visualization as an image file hover over the top right area of
the visualization and click the camera icon. It will be downloaded to your device.

##### Sending a shareable link

If you wish to send a link to someone without an account add the queries you
wish to share to a dashboard. You can do this using the ellipsis menu on your
dashboard and then by selecting add widget:

Select the name of the query you wish to add and click 'Add to Dashboard':

Once you've added the queries you wish to share, on the dashboard page click the
share icon:

Then tick the checkbox to generate a shareable url:
<img src="https://user-images.githubusercontent.com/16775804/34619613-a45f0e46-f23a-11e7-8294-e8b8bde4dfac.png" width=400px />

If you want to make sure the external user has access to the latest live data
you can set your dashboard up with a regular refresh. Click 'Refresh' to open a
dropdown with options of how regularly to refresh the query on the dashboard.

### Can I hide a field/column of my database on Redash?

You may want to query your data but you have one column which contains sensitive
data. Unfortunately it is not possible in Redash to hide or encrypt a portion of
your data. The best way to achieve this would be to create a seperate view of
your database. When you build that view only select the columns from each table
that you wish to include rather than selecting 'all'. Then connect the view of
your database up with Redash so the sensitive fields are no longer included.

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