Ò׽ؽØÍ¼Èí¼þ¡¢µ¥Îļþ¡¢Ãâ°²×°¡¢´¿ÂÌÉ«¡¢½ö160KB

MysqlÖÐcount(*),DISTINCTµÄʹÓ÷½·¨ºÍЧÂÊÑо¿

ÔÚ´¦ÀíÒ»¸ö´óÊý¾ÝÁ¿Êý¾Ý¿âµÄʱºò
ͻȻ·¢ÏÖmysql¶ÔÓÚcount(*)µÄ²»Í¬´¦Àí»áÔì³É²»Í¬µÄ½á¹û
±ÈÈçÖ´ÐÐ
SELECT count(*) from tablename
¼´Ê¹¶ÔÓÚǧÍò¼¶±ðµÄÊý¾ÝmysqlÒ²Äܷdz£Ñ¸Ëٵķµ»Ø½á¹û
¶ø¶ÔÓÚ
SELECT count(*) from tablename WHERE…..
mysqlµÄ²éѯʱ¼ä¿ªÊ¼ÅÊÉý
×Ðϸ²éÔÄÀÛÏÂÊÖ²á,·¢ÏÖµ±Ã»ÓÐWHEREÓï¾ä¶ÔÓÚÕû¸ömysqlµÄ±í½øÐÐcountÔËËãµÄʱºò
MyISAMÀàÐ͵ıíÖб£´æÓÐ×ܵÄÐÐÊý,¶øµ±Ìí¼ÓÓÐWHEREÏÞ¶¨Óï¾äµÄʱºòMysqlÐèÒª¶ÔÕû¸ö±í½øÐмìË÷
´Ó¶øµÃ³öcountµÄÊýÖµ
ͻȻÓÖÏëÆðÀ´¿´µ½µÄ²»ÉÙÐÂÐ˵Äphp³ÌÐò¶ÔÓÚcountµÄ´¦Àí²¢Ã»ÓкܺõÄÒâʶµ½Õâµã
¼Ç¼ÏÂ
˳±ãÌáÏÂmysqlµÄDISTINCTµÄ¹Ø¼ü×ÖÓкܶàÄãÏë²»µ½µÄÓô¦
1.ÔÚcount ²»Öظ´µÄ¼Ç¼µÄʱºòÄÜÓõ½
±ÈÈçSELECT COUNT( DISTINCT id ) from tablename;
¾ÍÊǼÆËãtalbebname±íÖÐid²»Í¬µÄ¼Ç¼ÓжàÉÙÌõ
2,ÔÚÐèÒª·µ»Ø¼Ç¼²»Í¬µÄidµÄ¾ßÌåÖµµÄʱºò¿ÉÒÔÓÃ
±ÈÈçSELECT DISTINCT id from tablename;
·µ»Øtalbebname±íÖв»Í¬µÄidµÄ¾ßÌåµÄÖµ
3.ÉÏÃæµÄÇé¿ö2¶ÔÓÚÐèÒª·µ»Ømysql±íÖÐ2ÁÐÒÔÉϵĽá¹ûʱ»áÓÐÆçÒå
±ÈÈçSELECT DISTINCT id, type from tablename;
ʵ¼ÊÉÏ·µ»ØµÄÊÇ idÓëtypeͬʱ²»ÏàͬµÄ½á¹û,Ò²¾ÍÊÇDISTINCTͬʱ×÷ÓÃÁËÁ½¸ö×ֶΣ¬±ØÐëµÃidÓëtyoe¶¼ÏàͬµÄ²Å±»ÅųýÁË,ÓëÎÒÃÇÆÚÍûµÄ½á¹û²»Ò»Ñù
4.Õâʱºò¿ÉÒÔ¿¼ÂÇʹÓÃgroup_concatº¯ÊýÀ´½øÐÐÅųý,²»¹ýÕâ¸ömysqlº¯ÊýÊÇÔÚmysql4.1ÒÔÉϲÅÖ§³ÖµÄ
5.Æäʵ»¹ÓÐÁíÍâÒ»ÖÖ½â¾ö·½Ê½,¾ÍÊÇʹÓÃ
SELECT id, type, count(DISTINCT id) from tablename
ËäÈ»ÕâÑùµÄ·µ»Ø½á¹û¶àÁËÒ»ÁÐÎÞÓõÄcountÊý¾Ý(»òÐíÄã¾ÍÐèÒªÕâ¸öÎÒ˵µÄÎÞÓÃÊý¾Ý)
·µ»ØµÄ½á¹ûÊÇ Ö»ÓÐid²»Í¬µÄËùÓнá¹ûºÍÉÏÃæµÄ4ÀàÐÍ¿ÉÒÔ»¥²¹Ê¹ÓÃ,¾ÍÊÇ¿´ÄãÐèҪʲôÑùµÄÊý¾ÝÁË
PS:
Ô½À´Ô½·¢ÏÖÓкܶàϸ½ÚÊÇÐèҪȥ̽¾¿µÄ,
Ô½À´Ô½·¢ÏÖ×Ô¼ºÐ´ÎÄ×ÖÕæµÄºÜÔÓÂÒ,
ÓпÕÑо¿ÏÂDISTINCTµÄЧÂÊ


Ïà¹ØÎĵµ£º

½âѹ°æ/Ãâ°²×°°æMySQLÅäÖÃÈ«½â

Ò» ÏÂÔØMySQL
http://dev.mysql.com/downloads/mysql/5.0.html
½âѹMySQL£¨F:\Program Files\MySQL\£©MySQL°²×°Ä¿Â¼
¶þ н¨my.ini
ÔÚF:\Program Files\MySQL\Ͻ¨Á¢my.iniÎļþ£¬ÄÚÈÝΪ
my.ini
[mysqld]
# ÉèÖÃmysqlµÄ°²×°Ä¿Â¼
basedir=F:\\Program Files\\MySQL
# ÉèÖÃmysqlÊý¾Ý¿âµÄÊý¾ÝµÄ´æ·ÅĿ¼£¬±ØÐ ......

½â¾ö.netÁ¬½ÓmysqlÂÒÂë

µ±mysqlÊý¾Ý¿âΪGBK±àºÅ£¬.net³ÌÐòʹÓÃĬÈϱàÂ루UTF-8£©£¬ÏòmysqlÖвåÈëÊý¾ÝÈÝÒײúÉúÂÒÂë¡£½â¾ö°ì·¨ÊÇÔÚÁ¬½Ó×Ö·û´®¼ÓÈëCharset=gbk£º
MySqlConnection myConnection = new MySqlConnection("Database=test2;Data Source=localhost;User Id=root;Password=ikmbikmb;Charset=gbk"); ......

linuxÏ mysqlÓû§µÄ¹ÜÀí

linux
ÏÂ mysql
Óû§µÄ¹ÜÀí
ÎÄÕ·ÖÀà:Êý¾Ý¿â
¹Ø¼ü×Ö: linux
mysql
Óû§¹ÜÀí

×Ô´ÓÉÏÔÚredhat Enterprise 5 Öа²×°ÁËMySQL
,Õâ´ÎÀ´Êµ¼ù²Ù×÷Ò»ÏÂMySQL
Óû§µÄ¹ÜÀí£»
 Ò»¡¢rootÓû§ÃÜÂëµÄά»¤£º
       ÓÉÓÚ°²×°MySQL
Íêºó,MySQL
»á×Ô¶¯Ìṩһ¸ö²»´ø ......

MySQL phpMyAdmin °²×°

Ê×ÏȰ²×°phpMyadmin
[root@aladdin phpMyAdmin]# uname -a
Linux aladdin.leadtek.com.cn 2.6.32.11-99.fc12.i686.PAE #1 SMP Mon Apr 5 16:15:03 EDT 2010 i686 i686 i386 GNU/Linux
[root@aladdin phpMyAdmin]# yum info phpmyadmin
Loaded plugins: presto, refresh-packagekit
Installed Packages
Name &nbs ......
© 2009 ej38.com All Rights Reserved. ¹ØÓÚE½¡ÍøÁªÏµÎÒÃÇ | Õ¾µãµØÍ¼ | ¸ÓICP±¸09004571ºÅ