There is no real way to extract browser name and version from browser agent header. Inspired from this links, i propose my query suggest :

/*
* Extract distinct browser+version from a table named "web_log" with http user agent stored in column "HTTP_USER_AGENT"
*/
-- SELECT COUNT( * ) AS `Lines` , `BROWSER` , `HTTP_USER_AGENT`
SELECT COUNT( * ) AS `Lines` , `BROWSER`
FROM (
SELECT
	CASE
/*
Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)
*/
	WHEN `HTTP_USER_AGENT` REGEXP 'MSIE [[:alnum:]]+.[[:alnum:]]+' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('MSIE ', `HTTP_USER_AGENT`), LOCATE(';', `HTTP_USER_AGENT`, LOCATE('MSIE ', `HTTP_USER_AGENT`))-LOCATE('MSIE ', `HTTP_USER_AGENT`))
/*
Mozilla/5.0 (Windows; U; Windows NT 6.0; fr; rv:1.9.2) Gecko/20100115 AskTbORJ/3.15.15.36191 Firefox/3.6 ( .NET CLR 3.5.30729; .NET4.0C)
Mozilla/5.0 (Windows NT 5.1; rv:19.0) Gecko/20100101 Firefox/19.0
*/	
	WHEN `HTTP_USER_AGENT` REGEXP 'Firefox/[[:alnum:]]+.[[:alnum:]]+' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('Firefox/', `HTTP_USER_AGENT`))
/*
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.116 Safari/537.36
*/
	WHEN `HTTP_USER_AGENT` REGEXP 'Chrome/[[:alnum:]]+.[[:alnum:]]+' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('Chrome/', `HTTP_USER_AGENT`))
/*
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_5_8) AppleWebKit/534.50.2 (KHTML, like Gecko) Version/5.0.6 Safari/533.22.3
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/534.58.2 (KHTML, like Gecko) Version/5.1.8 Safari/534.58.2
*/
	WHEN `HTTP_USER_AGENT` REGEXP 'Safari/[[:alnum:]]+.[[:alnum:]]+' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('Safari/', `HTTP_USER_AGENT`))
/*
Mozilla/5.0 (Windows; U; Windows NT 6.1; fr; rv:1.9.1.16) Gecko/20101123 SeaMonkey/2.0.11
*/
	WHEN `HTTP_USER_AGENT` REGEXP 'SeaMonkey/[[:alnum:]]+.[[:alnum:]]+' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('SeaMonkey/', `HTTP_USER_AGENT`))
/*
HTC_Touch_HD_T8282-orange/PPC; 480x800; OpVer 34.159.2.733 Opera/9.50(Microsoft Windows 5.1; U;fr)
PPC; 480x800; HTC_HD2_T8585-Orange; OpVer 156.314.2.732 Opera/9.7 (Microsoft Windows 6.5; U;fr)
Opera/9.80 (Windows Mobile; Opera Mini/5.1.21594/28.1914; U; fr) Presto/2.8.119 Version/11.10
Opera/9.80 (S60; SymbOS; Opera Mobi/1209; U; fr) Presto/2.5.28 Version/10.1
*/
-- WHEN `HTTP_USER_AGENT` REGEXP '^Opera/[[:alnum:]]+.[[:alnum:]]+ ' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('Opera/', `HTTP_USER_AGENT`), LOCATE(' ', `HTTP_USER_AGENT`, LOCATE('Opera/', `HTTP_USER_AGENT`))-LOCATE('Opera/', `HTTP_USER_AGENT`))
	WHEN `HTTP_USER_AGENT` REGEXP 'Opera/[[:alnum:]]+.[[:alnum:]]+ ' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('Opera/', `HTTP_USER_AGENT`), LOCATE(' ', `HTTP_USER_AGENT`, LOCATE('Opera/', `HTTP_USER_AGENT`))-LOCATE('Opera/', `HTTP_USER_AGENT`))
/*
Mozilla/5.0 (SAMSUNG; SAMSUNG-GT-S8530-ORANGE/S8530BVJL2; U; Bada/1.2; fr-fr) AppleWebKit/533.1 (KHTML, like Gecko) Dolfin/2.2 Mobile WVGA SMM-MMS/1.2.0 NexPlayer/3.0 profile/MIDP-2.1 configuration/CLDC-1.1 OPN-B
Mozilla/5.0 (SAMSUNG; SAMSUNG-GT-S8600-ORANGE/S8600BVKK3; U; Bada/2.0; fr-fr) AppleWebKit/534.20 (KHTML, like Gecko) Dolfin/3.0 Mobile WVGA SMM-MMS/1.2.0 NexPlayer/3.0 profile/MIDP-2.1 configuration/CLDC-1.1 OPN-B
*/
	WHEN `HTTP_USER_AGENT` REGEXP 'Dolfin/[[:alnum:]]+.[[:alnum:]]+ ' THEN SUBSTRING(`HTTP_USER_AGENT`, LOCATE('Dolfin/', `HTTP_USER_AGENT`), LOCATE(' ', `HTTP_USER_AGENT`, LOCATE('Dolfin/', `HTTP_USER_AGENT`))-LOCATE('Dolfin/', `HTTP_USER_AGENT`))
/*
Mozilla/5.0 (iPad; CPU OS 6_1_3 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Mobile/10B329
AppleCoreMedia/1.0.0.10B329 (iPhone; U; CPU OS 6_1_3 like Mac OS X; fr_fr)
+--------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Lignes | BROWSER | HTTP_USER_AGENT                                                                                                                                                                |
+--------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|   6381 | UNKNOW  | HTC_Touch_HD_T8282-orange/PPC; 480x800; OpVer 34.159.2.733 Opera/9.50(Microsoft Windows 5.1; U;fr)                                                                             |
|    270 | UNKNOW  | SAMSUNG-GT-S5230-Bouygues/S5230AGIF2 SHP/VPP/R5 Jasmine/0.8 Nextreaming SMM-MMS/1.2.0 profile/MIDP-2.1 configuration/CLDC-1.1                                                  |
|    180 | UNKNOW  | Mozilla/5.0 (Symbian/3; Series60/5.2 NokiaC7-00/013.016; Profile/MIDP-2.1 Configuration/CLDC-1.1 ) AppleWebKit/525 (KHTML, like Gecko) Version/3.0 BrowserNG/7.2.8.10 3gpp-gba |
|     13 | UNKNOW  | Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; fr-fr) AppleWebKit/533.17.9 (KHTML, like Gecko) Mobile/8C148                                                        |
|      2 | UNKNOW  | NULL                                                                                                                                                                           |
|      1 | UNKNOW  | HTC_Touch_HD_T8282-orange/PPC; 480x800; OpVer 34.119.2.731 Opera/9.50(Microsoft Windows 5.1; U;fr)                                                                             |
+--------+---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
*/
	ELSE 'UNKNOW'
	END AS BROWSER
	, `HTTP_USER_AGENT`
FROM `web_log` 
-- WHERE HTTP_USER_AGENT LIKE '%opera%'
-- WHERE `date` > '2012-01-01 00:00:00'
) AS table_user_agent_filtred
-- WHERE `BROWSER` = 'UNKNOW'
GROUP BY `BROWSER` 
-- GROUP BY `BROWSER`, `HTTP_USER_AGENT` 
ORDER BY `Lines` DESC 
;
-- 149 rows in set (3 min 52.73 sec)
 
/*
+--------+-------------------------------------------+
| Lines | BROWSER                                   |
+--------+-------------------------------------------+
| 372929 | Safari/533.1                              |
| 164338 | Chrome/23.0.1271.97 Safari/537.11         |
|  98857 | MSIE 8.0                                  |
|  97130 | MSIE 9.0                                  |
|  68900 | Firefox/14.0.1                            |
|  67151 | MSIE 6.0                                  |
|  54835 | Opera/9.80                                |
|  52894 | Chrome/12.0.742.112 Safari/534.30         |
|  52333 | Chrome/22.0.1229.94 Safari/537.4          |
|  50105 | Chrome/23.0.1271.95 Safari/537.11         |
|  37141 | Chrome/23.0.1271.64 Safari/537.11         |
|  33968 | Chrome/21.0.1180.89 Safari/537.1          |
|  31009 | Firefox/15.0.1                            |
|  27596 | Chrome/20.0.1132.57 Safari/536.11         |
|  26947 | Chrome/19.0.1084.56 Safari/536.5          |
|  25467 | Chrome/19.0.1084.52 Safari/536.5          |
|  20457 | Safari/530.17                             |
|  19488 | Chrome/22.0.1229.79 Safari/537.4          |
|  19255 | Chrome/24.0.1312.52 Safari/537.17         |
|  18824 | Safari/7534.48.3                          |
|  18449 | Chrome/21.0.1180.83 Safari/537.1          |
|  18053 | Firefox/13.0.1                            |
|  18018 | Opera/9.5                                 |
|  17528 | Chrome/20.0.1132.47 Safari/536.11         |
|  16649 | Firefox/16.0                              |
|  15875 | Firefox/12.0                              |
|  14798 | Chrome/17.0.963.56 Safari/535.11          |
|  13927 | Chrome/16.0.912.75 Safari/535.7           |
|  13898 | Firefox/17.0                              |
|  13133 | Chrome/16.0.912.77 Safari/535.7           |
|  12443 | Safari/8536.25                            |
|  11716 | Firefox/13.0                              |
|  11345 | Firefox/15.0                              |
|  11189 | MSIE 7.0                                  |
|  11051 | Opera/9.50                                |
|  10205 | Chrome/18.0.1025.162 Safari/535.19        |
|   8705 | Safari/6533.18.5                          |
|   8398 | Chrome/21.0.1180.60 Safari/537.1          |
|   7826 | Chrome/24.0.1312.56 Safari/537.17         |
|   7086 | Chrome/18.0.1025.168 Safari/535.19        |
|   6977 | Firefox/11.0                              |
|   6847 | UNKNOW                                    |
|   6301 | Chrome/21.0.1180.79 Safari/537.1          |
|   5526 | Chrome/23.0.1271.91 Safari/537.11         |
|   5422 | Chrome/16.0.912.63 Safari/535.7           |
|   5129 | Chrome/17.0.963.79 Safari/535.11          |
|   4785 | Firefox/10.0.2                            |
|   4614 | Chrome/21.0.1180.75 Safari/537.1          |
|   4449 | Chrome/17.0.963.83 Safari/535.11          |
|   3841 | Chrome/18.0.1025.152 Safari/535.19        |
|   3585 | Chrome/18.0.1025.142 Safari/535.19        |
|   3500 | Firefox/9.0.1                             |
|   3454 | Opera/9.7                                 |
|   3258 | Firefox/18.0                              |
|   3255 | Firefox/10.0.4 Fennec/10.0.4              |
|   3126 | Chrome/22.0.1229.92 Safari/537.4          |
|   2969 | Chrome/19.0.1084.46 Safari/536.5          |
|   2709 | Chrome/17.0.963.78 Safari/535.11          |
|   2599 | Chrome/4.1.249.1045 Safari/532.5          |
|   2449 | Chrome/17.0.963.46 Safari/535.11          |
|   2300 | Safari/525.20.1                           |
|   1643 | Firefox/13.0 Fennec/13.0                  |
|   1621 | Safari/533.1 MMS/LG-Android-MMS-V1.0/1.2  |
|   1587 | Chrome/17.0.963.66 Safari/535.11          |
|   1414 | Chrome/15.0.874.121 Safari/535.2          |
|   1358 | Safari/534.30                             |
|   1265 | Firefox/8.0                               |
|   1208 | Firefox/9.0 Fennec/9.0                    |
|   1151 | Chrome/21.0.1180.77 Safari/537.1          |
|   1108 | Firefox/10.0.1                            |
|    760 | Safari/534.8+                             |
|    660 | Firefox/10.0.3 Fennec/10.0.3              |
|    635 | Safari/6531.22.7                          |
|    493 | Chrome/18.0.1025.151 Safari/535.19        |
|    472 | Firefox/10.0                              |
|    385 | Firefox/10.0.2 Fennec/10.0.2              |
|    382 | Chrome/22.0.1229.96 Safari/537.4          |
|    378 | Firefox/10.0.5 Fennec/10.0.5              |
|    193 | Firefox/21.0                              |
|    174 | Firefox/3.6.3 (.NET CLR 3.5.30729)        |
|    169 | Firefox/10.0 Fennec/10.0                  |
|    166 | Firefox/19.0                              |
|    137 | Firefox/20.0                              |
|    100 | Chrome/17.0.963.65 Safari/535.11          |
|     98 | Firefox/10.0.1 Fennec/10.0.1              |
|     82 | Chrome/19.0.1084.54 Safari/536.5          |
|     69 | Firefox/14.0                              |
|     66 | Firefox/7.0                               |
|     57 | Chrome/18.0.1025.163 Safari/535.19        |
|     53 | Chrome/18.0.1025.165 Safari/535.19        |
|     52 | Firefox/9.0                               |
|     46 | Firefox/8.0.1                             |
|     43 | MSIE 10.0                                 |
|     43 | Firefox/22.0                              |
|     38 | Chrome/26.0.1410.64 Safari/537.31         |
|     32 | Chrome/25.0.1364.172 Safari/537.22        |
|     29 | Safari/534.13                             |
|     23 | Safari/536.25                             |
|     16 | Chrome/18.0.1025.166 Mobile Safari/535.19 |
|     14 | Safari/525                                |
|     12 | Safari/534.52.7                           |
|     12 | Chrome/12.0.742.122 Safari/534.30         |
|     11 | Chrome/20.0.1087.0 Safari/536.6           |
|     10 | Safari/536.26.14                          |
|      8 | Firefox/8.0 webissimo3/3.4.11+svn138183.0 |
|      7 | Safari/534.57.2                           |
|      7 | Safari/533.22.3                           |
|      7 | Firefox/3.6.8 ( .NET CLR 3.5.30729)       |
|      6 | Chrome/11.0.696.34 Safari/534.24          |
|      5 | Chrome/6.0.495.0 Safari/534.6             |
|      5 | Firefox/7.0.1                             |
|      4 | Safari/534.55.3                           |
|      4 | Safari/534.56.5                           |
|      3 | Dolfin/2.2                                |
|      3 | Firefox/3.6.13 (.NET CLR 3.5.30729)       |
|      3 | Safari/536.26.17                          |
|      1 | Safari/531.21.10                          |
|      1 | Dolfin/3.0                                |
+--------+-------------------------------------------+
118 rows in set (3 min 26.34 sec)
*/