# MySQL

## Prerequisites

- The hostname for the [MySQL][mysql] database server
- The username/password for the [MySQL][mysql] database server
- The name of the database to use within the [MySQL][mysql] database server

## Setup

### Manual

Add the following to a `.env` file in your Cube project:

```dotenv
CUBEJS_DB_TYPE=mysql
CUBEJS_DB_HOST=my.mysql.host
CUBEJS_DB_NAME=my_mysql_database
CUBEJS_DB_USER=mysql_user
CUBEJS_DB_PASS=**********
```

## Environment Variables

| Environment Variable    | Description                                                                         | Possible Values           | Required |
| ----------------------- | ----------------------------------------------------------------------------------- | ------------------------- | :------: |
| <EnvVar>CUBEJS_DB_HOST</EnvVar>        | The host URL for a database                                                         | A valid database host URL |    ✅    |
| <EnvVar>CUBEJS_DB_SOCKET_PATH</EnvVar> | See [connecting via a Unix socket](#connecting-via-a-unix-socket)                   | A valid path to a socket  |    ❌    |
| <EnvVar>CUBEJS_DB_PORT</EnvVar>        | The port for the database connection                                                | A valid port number       |    ❌    |
| <EnvVar>CUBEJS_DB_NAME</EnvVar>        | The name of the database to connect to                                              | A valid database name     |    ✅    |
| <EnvVar>CUBEJS_DB_USER</EnvVar>        | The username used to connect to the database                                        | A valid database username |    ✅    |
| <EnvVar>CUBEJS_DB_PASS</EnvVar>        | The password used to connect to the database                                        | A valid database password |    ✅    |
| <EnvVar>CUBEJS_DB_SSL</EnvVar>         | If `true`, enables SSL encryption for database connections from Cube                | `true`, `false`           |    ❌    |
| <EnvVar>CUBEJS_DB_MAX_POOL</EnvVar>    | The maximum number of concurrent database connections to pool. Default is `8`       | A valid number            |    ❌    |
| <EnvVar>CUBEJS_DB_MYSQL_USE_NAMED_TIMEZONES</EnvVar> | The flag to use time zone names or numeric offsets for time zone conversion. Default is `false` | `true`, `false` | ❌ |
| <EnvVar>CUBEJS_CONCURRENCY</EnvVar> | The number of [concurrent queries][ref-data-source-concurrency] to the data source | A valid number |    ❌    |

[ref-data-source-concurrency]: /product/configuration/concurrency#data-source-concurrency

## Pre-Aggregation Feature Support

### count_distinct_approx

Measures of type
[`count_distinct_approx`][ref-schema-ref-types-formats-countdistinctapprox] can
not be used in pre-aggregations when using MySQL as a source database.

## Pre-Aggregation Build Strategies

<InfoBox>

To learn more about pre-aggregation build strategies, [head
here][ref-caching-using-preaggs-build-strats].

</InfoBox>

| Feature       | Works with read-only mode? | Is default? |
| ------------- | :------------------------: | :---------: |
| Batching      |             ✅             |     ✅      |
| Export Bucket |             -              |      -      |

By default, MySQL uses [batching][self-preaggs-batching] to build
pre-aggregations.

### Batching

No extra configuration is required to configure batching for MySQL.

### Export Bucket

MySQL does not support export buckets.

## SSL

To enable SSL-encrypted connections between Cube and MySQL, set the
<EnvVar>CUBEJS_DB_SSL</EnvVar> environment variable to `true`. For more information on how to
configure custom certificates, please check out [Enable SSL Connections to the
Database][ref-recipe-enable-ssl].

## Additional configuration

### Connecting via a Unix socket

To connect to a local MySQL database using a Unix socket, use the
<EnvVar>CUBEJS_DB_SOCKET_PATH</EnvVar> environment variable, for example:

```dotenv
CUBEJS_DB_SOCKET_PATH=/var/run/mysqld/mysqld.sock
```

When doing so, <EnvVar>CUBEJS_DB_HOST</EnvVar> will be ignored.

### Connecting to MySQL 8

MySQL 8 is fully supported and uses the new default authentication plugin
(`caching_sha2_password`). No additional configuration is required.

[mysql]: https://www.mysql.com/
[ref-caching-using-preaggs-build-strats]:
  /product/caching/using-pre-aggregations#pre-aggregation-build-strategies
[ref-recipe-enable-ssl]:
  /product/configuration/recipes/using-ssl-connections-to-data-source
[ref-schema-ref-types-formats-countdistinctapprox]: /product/data-modeling/reference/types-and-formats#count_distinct_approx
[self-preaggs-batching]: #batching
