Use `ddev describe` to see what the host and port are for your local environment, and use that in the first line here:
```
mysql --host=127.0.0.1 --port=32779 --user=root --password=root --database=db
CREATE DATABASE drupal7;
GRANT ALL ON drupal7.* to 'db'@'%' IDENTIFIED BY 'db';
```
Now `ctrl+c` out of there, and, again substituting the host and port for your own, import your file from whereever you placed and named your db SQL dump:
```
mysql --host=127.0.0.1 --port=32779 --user=root --password=root --database=drupal7 <data/db.sql`
```
(Per [instructions for creating another database in ddev](https://stackoverflow.com/a/49785024/1943924).)