쿼리문 해석부탁드립니다. 채택완료

http://minsw.waplez.com/myadmin/url.php?url=http%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.1%2Fen%2Fselect.html&token=98bce8923c54f85263c6d25a06054f1c" target="mysql_doc" style="text-decoration: none; color: rgb(35, 90, 129); cursor: pointer; outline: none; border-bottom: 1px dotted black; font-family: Verdan, Arial, Tahoma; font-size: 14.432px; background-color: rgb(229, 229, 229);">SELECT * FROM `g5_board` a http://minsw.waplez.com/myadmin/url.php?url=http%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.1%2Fen%2Fstring-functions.html%23function_left&token=98bce8923c54f85263c6d25a06054f1c" target="mysql_doc" style="text-decoration: none; color: rgb(35, 90, 129); cursor: pointer; outline: none; border-bottom: 1px dotted black; font-family: Verdan, Arial, Tahoma; font-size: 14.432px; background-color: rgb(229, 229, 229);">LEFT JOIN `g5_group` b ON ( a.gr_id http://minsw.waplez.com/myadmin/url.php?url=http%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.1%2Fen%2Fcomparison-operators.html%23operator_equal&token=98bce8923c54f85263c6d25a06054f1c" target="mysql_doc" style="text-decoration: none; color: rgb(35, 90, 129); cursor: pointer; outline: none; border-bottom: 1px dotted black; font-family: Verdan, Arial, Tahoma; font-size: 14.432px; background-color: rgb(229, 229, 229);">= b.gr_id ) 
WHERE a.bo_device http://minsw.waplez.com/myadmin/url.php?url=http%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.1%2Fen%2Fcomparison-operators.html%23operator_not-equal&token=98bce8923c54f85263c6d25a06054f1c" target="mysql_doc" style="text-decoration: none; color: rgb(35, 90, 129); cursor: pointer; outline: none; border-bottom: 1px dotted black; font-family: Verdan, Arial, Tahoma; font-size: 14.432px; background-color: rgb(229, 229, 229);"><> 'mobile'
LIMIT 0 , 30 

g5_board 테이블을 a

g5_group 테이블을 b 라고 정하고 

(a.gr_id = b.gr_id) WHERE a.bo_device http://minsw.waplez.com/myadmin/url.php?url=http%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F5.1%2Fen%2Fcomparison-operators.html%23operator_not-equal&token=98bce8923c54f85263c6d25a06054f1c" target="mysql_doc" style="text-decoration: none; color: rgb(35, 90, 129); cursor: pointer; outline: none; border-bottom: 1px dotted black; font-family: Verdan, Arial, Tahoma; font-size: 14.432px; background-color: rgb(229, 229, 229);"><> 'mobile'

g5_board 테이블의 gr_id 와 g5_group 테이블의 gr_id와 같은값을 불러오는거 아닌가요??