mysqlÖÐcountº¯Êý×¢ÒâÊÂÏî
񡜧
CREATE TABLE `user` (
`id` int(5) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(10) DEFAULT NULL,
`password` varchar(10) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=latin1
ÆäÖÐÓÐÊý¾ÝΪ£º
1 name1 123456
2 name2 123456
3 name3 123456
4 name4 NULL
ÒÔÏÂÈý¸ö²éѯ·µ»Ø¼¸ÄØ£¿
£¨1£©select count(*) from `user`
£¨2£©select count(name) from `user`
£¨3£©select count(password) from `user`
´ð°¸ÊÇ£º4,4,3
ÒòΪ£º
£¨1£©count(*)ÊǶÔÐÐÊýÄ¿½øÐмÆÊý£¬ËùÒÔµ±È»ÊÇ4
£¨2£©count(column_name)ÊǶÔÁÐÖв»Îª¿ÕµÄÐнøÐмÆÊý£¬ËùÒÔcount(name)=4£¬¶øcount(password)=3
Ïà¹ØÎĵµ£º
MySQL ClusterÅäÖÃstep by step
À´Ô´£ºhttp://space.itpub.net/15415488/viewspace-620903
¹«Ë¾ÓиöÏîÄ¿ÊDzâÊÔdistributed DB£¬ÆäÖÐÒ»ÏîÊÇÕë¶ÔMySQL ClusterµÄ²âÊÔ¡£
ÓÚÊÇ»¨ÁËÁ½Ììʱ¼ä×°»úÆ÷ºÍÅäÖÃMySQL Cluster¡£Õû¸ö¹ý³Ì»¹ÊDZȽÏ˳ÀûµÄ£¬µ±È»Èç¹û¶ÔMySQL³£ÓÃÃüÁî±È½ÏÊìϤµÄ»°»á¸ü˳Àû¡£
ÁôÏÂstep by stepÅä ......
ÕâÀïÊ×ÏÈ˵ÏÂoracle·ÖÒ³²»Ïñmysql·ÖÒ³ÄÇô¼òµ¥Ö±½Ólimit ¾Í¿ÉÒÔÁË.
mysql£ºsql ="select * from talbe limit 0,10";
µÚÒ»¸öÊý±íʾϱ꣬¾ÍÊÇ´ÓµÚ¼¸ÌõÊý¾Ý¿ªÊ¼£¬
µÚ¶þ¸öÊý±íʾÿҳÏÔʾ¶àÉÙÌõÊý¾Ý£¬¿ÉÒÔ˵Êǵ±ÄãÈ·¶¨Ã¿Ò³ÏÔʾ¶àÉÙÐÐʱºò£¬Ëü¾ÍÊÇÒ»¸ö¹Ì¶¨µÄÊý¡£
ÕâÀïÐèҪעÒâµÄÊÇ£¬mysqlµÄ·ÃÎÊϱêÊÇ´Ó0¿ªÊ¼µÄ¡£Õ ......
1. Á¬½Ómysql:
mysql -h Ö÷»úµØÖ· -u Óû§Ãû £p
2.Í˳ömysql:exit
3. ÐÞ¸ÄÃÜÂë:
mysqlbinmysqladmin -uroot -p(oldpassword) password newpassword
4.Ôö¼ÓÓû§£º
Ìí¼ÓÒ»¸öÓû§test1 ÃÜÂëΪABC£»ÈÃËû¿ÉÒÔÔÚÈκÎÖ÷»úÉϵǼ,²¢¶ÔËùÓÐÊý¾Ý¿âÓвéѯ¡¢²åÈë¡¢Ð޸ġ¢É¾³ýµÄȨÏÞ¡£Ê×ÏÈÓÃÒÔrootÓû§Á¬Èë
mysql,È»ºó¼üÈëÒÔÏÂÃü ......
¶ÔmysqlµÄÓÅ»¯²»ÔÚÐУ¬¸ã¹ý¼¸´ÎÓÅ»¯£¬µ«ÊǶ¼²»ÊǺÜÀíÏ룬»¹ÊÇÀË·Ñ×ÊÔ´Ì«¶à¡£Ò»Ö±·¢ÏÖÎÒµÄmysqlµÄ»º´æÃüÖÐÂʼ«²î£¬Çé¿öÁ¼ºÃµÄʱºòµ½´ï¹ý60-70%£¬µ«ÊÇÔËÐÐʱ¼äÒ»³¤£¬Ö»ÓÐ10-20%¡£²éÁËһЩ×ÊÁÏ£¬¹ØÓÚ»º´æµÄһЩ²ÎÊý¼Ç¼
mysql> SHOW VARIABLES LIKE ‘%query_cache%’;
+—————&m ......
ÎÒÓÐÒ»¸ö±í
CREATE TABLE `test1` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`desc` varchar(100) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
£¨1£©ÒÔϲéѯ»á±¨´íÎó£º[Err] 1221 - Incorrect usage of UNION and ORDE ......