MySQLÖÐÓÃselectʵÏÖTOP N¹¦ÄÜ ¼°·ÖÒ³
MySQLÖÐÓÃselectʵÏÖTOP N¹¦ÄÜ
ÏÈ˵¼¸¸ö¹Ø¼ü×Ö£º
distinct ·µ»Ø²»Öظ´µÄ¶àÁÐ
count() ¼ÆÊý
limit m,n µÚm¸öÆðn¸ö
ÄÇô£¬Èç¹ûÐèÒª²éÕÒÃûΪcolµÄijһ¸öÁеÄTop N£¬²¢Áгö¶ÔÓ¦µÄÖµµÄselectÓï¾ä¾ÍÈçÏ£º
select dinstinct(col),count(col) from tablename group by 1 order by 2 desc limit 0,N;
Ïà¹ØÎĵµ£º
MysqlĬÈϵıàÂëÊÇlatin1£¬ËùÒÔͨ¹ýSqlyog»òÕßJava³ÌÐò¶ÁдÊý¾Ý¿âʱ£¬ÖÐÎͼ½«ÏÔʾΪÂÒÂ룬µ«ÔÚ¿ØÖÆÌ¨Í¨¹ýÃüÁîÐпÉÒÔÏÔʾÖÐÎÄ¡£
ÈçºÎ½â¾öÖÐÎÄÂÒÂëÎÊÌâÄØ£¬¸Ä±äMysqlϵͳµÄ±àÂ뷽ʽ£¬ÔÚMySqlĿ¼ÏµÄmy.iniÎļþÖеÄdefault-character-set=latin1¸ÄΪdefault-character-set=gbk(»òÆäËû),ÔÙÖØÆô·þÎñ¡£µ«ÈÔÈ»ÏÔʾΪÂÒÂ룬ÔÀ ......
×î½üÏëÔÚ·þÎñÆ÷ÉÏÊÔÊÔMySQL5.1µÄ·ÖÇø£¬ÓÚÊǾÍÏë×Å×°¸öMySQL5.1£¬¾¹ýÍ´¿àµÄÒ»¶Î¾Àúºó£¬ÖÕÓÚÕÒ¸öÏÂÃæ×°¸öºÜºÃµÄ½Ì³Ì£¬ÌûÉÏÀ´±¸Íü¡£
1¡¢MySQLÃâ°²×°°æ/¶þ½øÖưæÈí¼þ£¬²»ÓñàÒ룬ÏÂÔØµØÖ·£º
http://dev.mysql.com/downloads/
Îļþ¸ñʽ£ºMYSQL-VERSION-OS.tar.gz
2¡ ......
1)¡¢È¥sunµÄ¹ÙÍøÏÂÔØÒ»¸ömysqlµÄѹËõ°ü£¬ÎÒÏÂÔØµÄÊÇmysql-noinstall-5.5.0-m2-win32.zip¡£
2)¡¢°ÑÉÏÃæÏÂÔØµÄѹËõ°ü½âѹµ½£ºD:\Program Files\mysqlÏÂÃæ¡£
3)¡¢ÔÚ D:\Program Files\mysql\ ÖÐÕÒ my-large.ini °ÑËü¸´ÖÆ³É my.ini¡£
4)¡¢ÔÚ my.ini ÖÐÕÒ [mysqld] £¬Ìí ......
mysql×Ö·û¼¯²é¿´ÒÔ¼°ÐÞ¸Ä
http://blog.csdn.net/cs870101/archive/2009/09/23/4580879.aspx
ת×Ô:http://blog.chinaunix.net/u2/85344/showart_2042280.html
LiunxÏÂÐÞ¸ÄMySQL×Ö·û¼¯£º
1.²éÕÒMySQLµÄcnfÎļþµÄλÖÃ
find / -iname '*.cnf' -print
/usr/share/mysql/my-innodb-heavy-4G.cnf
/usr/share/mysql/my-la ......
mysqlÖÐchar¡¢varchar¡¢nvarcharÊý¾ÝÀàÐ͵ÄÓ÷¨Çø±ð:
˵Ã÷:
1¡¢char:
¹Ì¶¨³¤¶ÈµÄ·Ç Unicode ×Ö·ûÊý¾Ý£¬×î´ó³¤¶ÈΪ 8,000 ¸ö×Ö·û¡£
2¡¢varchar£º
¿É±ä³¤¶ÈµÄ·Ç Unicode Êý¾Ý£¬×Ϊ 8,000 ¸ö×Ö·û¡£
3¡¢nvarchar£º
¿É±ä³¤¶È Unicode Êý¾Ý£¬Æä×î´ó³¤¶ÈΪ 4,000 ×Ö·û¡£  ......