add usage directions

Author: some-natalie

sql/USAGE.md

@@ -1 +1,49 @@
 # Using the SQL queries
+
+The safest way to run these queries is by using the backup created by [backup-utils](https://github.com/github/backup-utils) loaded into another database server.  This database can be quite large and GitHub Enterprise Server can be sensitive to I/O intensive operations that aren't part of anticipated load.
+
+:warning:  This database contains sensitive information.  Please treat it appropriately within your company / network!
+
+A simple way to do this would be to install a MySQL 5.7 server on the VM receiving the backups and load it automatically.  You can then connect to in using `root` with no password, or whatever you set up for authentication.  What this looks like in practice would be similar to this shell script:
+
+```shell
+# Stop MySQL
+sudo systemctl stop mysqld.service
+
+# Unzip the most current backup
+gunzip -c /data/current/mysql.sql.gz > /data/mysql.tar
+
+# Untar the current backup
+tar xf /data/mysql.tar --directory=/home/github/restore-job/
+
+# Remove the temporary tarball
+rm /data/mysql.tar
+
+# Clear the data directory before restoring
+sudo rm -rf /var/lib/mysql-data/*
+
+# Run the Percona backup restore
+cd /home/github/restore-job && sudo innobackupex --defaults-file=backup-my.cnf --copy-back --datadir=/var/lib/mysql-data .
+
+# Restore the innodb buffer pool
+sudo cp -n /var/lib/mysql/ib_buffer_pool /var/lib/mysql-data/
+
+# Restore the innodb data
+sudo cp -n /var/lib/mysql/ibdata1 /var/lib/mysql-data/
+
+# Restore the first and second logs
+sudo cp -n /var/lib/mysql/ib_logfile0 /var/lib/mysql-data/
+sudo cp -n /var/lib/mysql/ib_logfile1 /var/lib/mysql-data/
+
+# Reset ownership
+sudo chown -R mysql:mysql /var/lib/mysql-data
+
+# Restore SELinux contexts (if applicable)
+sudo restorecon -R /var/lib/mysql-data
+
+# Start MySQL
+sudo systemctl start mysqld.service
+
+# Clear the working directory to save some disk space
+rm -rf /home/github/restore-job/*
+```