Q:

"Unable to to find SQL Class. Drush cannot find your Database connection details."

Just started with drupal and drush CLI but having problems already!
Here is my error:    
$ drush si --debug --db-url =mysql://USERNAME:PASSWORD@HOST/DATABASE/drushfun   
Starting Drush preflight. [0 sec, 1.29 MB]                                                                                                                                                      [preflight]
Cache HIT cid: 7.1.0-commandfiles-0-33a837c10472909bafe9ab29823ddb79 [0.01 sec, 1.32 MB]                                                                                                              [debug]
Bootstrap to phase 0. [0.06 sec, 3.52 MB]                                                                                                                                                         [bootstrap]
Bootstrap to phase 1. [0.06 sec, 3.52 MB]                                                                                                                                                         [bootstrap]
Drush bootstrap phase : bootstrap_drupal_root() [0.06 sec, 3.73 MB]                                                                                                                               [bootstrap]
Initialized Drupal 7.41 root directory at /home/USER/Documents//drupal-7.41fun [0.06 sec, 3.73 MB]                                                                           [notice]
Find command files for phase 1 (max=1) [0.07 sec, 2.71 MB]                                                                                                                                            [debug]
Cache HIT cid: 7.1.0-commandfiles-1-b9de3821d4a21c5d43292e8f9d7ffd3d [0.07 sec, 2.71 MB]                                                                                                              [debug]
Found command: site-install (commandfile=site_install) [0.07 sec, 2.71 MB]                                                                                                                        [bootstrap]
Calling hook drush_core_site_install_validate [0.09 sec, 3.75 MB]                                                                                                                                     [debug]
Returned from hook drush_core_site_install_validate [0.09 sec, 3.75 MB]                                                                                                                               [debug]
Calling hook drush_core_pre_site_install [0.09 sec, 3.76 MB]                                                                                                                                          [debug]
exception 'Drush\Sql\SqlException' with message 'Unable to find a matching SQL Class. Drush cannot find your database connection details.' in                                                     [error]
/home/USER/.composer/vendor/drush/drush/commands/sql/sql.drush.inc:597
Stack trace:
#0 /home/USER/.composer/vendor/drush/drush/commands/sql/sql.drush.inc(582): drush_sql_get_class(Array)
#1 /home/USER/.composer/vendor/drush/drush/commands/core/site_install.drush.inc(107): drush_sql_get_class()
#2 [internal function]: drush_core_pre_site_install('=mysql://root:r...')
#3 /home/USER/.composer/vendor/drush/drush/includes/command.inc(359): call_user_func_array('drush_core_pre_...', Array)
#4 /home/USER/.composer/vendor/drush/drush/includes/command.inc(210): _drush_invoke_hooks(Array, Array)
#5 [internal function]: drush_command('=mysql://root:r...')
#6 /home/USER/.composer/vendor/drush/drush/includes/command.inc(178): call_user_func_array('drush_command', Array)
#7 /home/USER/.composer/vendor/drush/drush/lib/Drush/Boot/BaseBoot.php(62): drush_dispatch(Array)
#8 /home/USER/.composer/vendor/drush/drush/drush.php(70): Drush\Boot\BaseBoot->bootstrap_and_dispatch()
#9 /home/USER/.composer/vendor/drush/drush/drush.php(11): drush_main()
#10 {main} [0.09 sec, 3.78 MB]
Command dispatch complete [0.09 sec, 3.75 MB]                                                                                                                                                        [notice]
$    

Here is what i have so far:    
$ drush status
Drupal version         :  7.41                                                         
Site URI               :  http://default                                               
PHP executable         :  /usr/bin/php                                                 
PHP configuration      :  /etc/php5/cli/php.ini                                        
PHP OS                 :  Linux                                                        
Drush script           :  /home/USER/.composer/vendor/drush/drush/drush.php           
Drush version          :  7.1.0                                                        
Drush temp directory   :  /tmp                                                         
Drush configuration    :                                                               
Drush alias files      :                                                               
Drupal root            :  /home/USER/Documents/drupal-7.41fun 
Site path              :   sites/default                                                

Why do i have that error? Am i missing something? Need to be able to work from the CLI.  
$ php -v
PHP 5.6.17-1+deb.sury.org~precise+1 (cli) 
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2015 Zend Technologies
with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2015, by Zend Technologies 

$ mysql --version
mysql  Ver 14.14 Distrib 5.5.46, for debian-linux-gnu (i686) using readline 6.2      

mysql> SELECT VERSION();
+-------------------------+
| VERSION()               |
+-------------------------+
| 5.5.46-0ubuntu0.12.04.2 |
+-------------------------+

A:

Drush options are space separated, so this:
drush si --debug --db-url =mysql://USERNAME:PASSWORD@HOST/DATABASE/drushfun   

Just needs to be:
drush si --debug --db-url=mysql://USERNAME:PASSWORD@HOST/DATABASE/drushfun   

(no space between --db-url and =)

