mysql ʹÓÃrandËæ»ú²éѯ¼Ç¼ЧÂʲâÊÔ
Ò»Ö±ÒÔΪmysqlËæ»ú²éѯ¼¸ÌõÊý¾Ý£¬¾ÍÓÃ
SELECT
*
from
`
table
`
ORDER
BY
RAND
() LIMIT
5
¾Í¿ÉÒÔÁË¡£
µ«ÊÇÕæÕý²âÊÔһϲŷ¢ÏÖÕâÑùЧÂʷdz£µÍ¡£Ò»¸ö15ÍòÓàÌõµÄ¿â£¬²éѯ5ÌõÊý¾Ý£¬¾ÓȻҪ8ÃëÒÔÉÏ
²é¿´¹Ù·½ÊֲᣬҲ˵rand()·ÅÔÚORDER BY ×Ó¾äÖлᱻִÐжà´Î£¬×ÔȻЧÂʼ°ºÜµÍ¡£
You cannot use a column with RAND() values in an ORDER BY clause,
because ORDER BY would evaluate the column multiple times.
ËÑË÷Google£¬ÍøÉÏ»ù±¾É϶¼ÊDzéѯmax(id) * rand()À´Ëæ»ú»ñÈ¡Êý¾Ý¡£
SELECT
*
from
`
table
`
AS
t1
JOIN
(
SELECT
ROUND
(
RAND
()
*
(
SELECT
MAX
(id)
from
`
table
`))
AS
id)
AS
t2
WHERE
t1.id
>=
t2.id
ORDER
BY
t1.id
ASC
LIMIT
5
;
µ«ÊÇÕâÑù»á²úÉúÁ¬ÐøµÄ5Ìõ¼Ç¼¡£½â¾ö°ì·¨Ö»ÄÜÊÇÿ´Î²éѯһÌõ£¬²éѯ5´Î¡£¼´±ãÈç´ËÒ²ÖµµÃ£¬ÒòΪ15ÍòÌõµÄ±í£¬²éѯֻÐèÒª0.01Ãë²»µ½¡£
ÉÏÃæµÄÓï¾ä²ÉÓõÄÊÇJOIN£¬mysqlµÄÂÛ̳ÉÏÓÐÈËʹÓÃ
SELECT
*
from
`
table
`
WHERE
id
>=
(
SELECT
FLOOR
(
MAX
(id)
*
RAND
())
from
`
table
` )
ORDER
BY
id LIMIT
1
;
ÎÒ²âÊÔÁËһϣ¬ÐèÒª0.5Ã룬ËÙ¶ÈÒ²²»´í£¬µ«ÊǸúÉÏÃæµÄÓï¾ä»¹ÊÇÓкܴó²î¾à¡£×ܾõÓÐʲôµØ·½²»Õý³£¡£
ÓÚÊÇÎÒ°ÑÓï¾ä¸ÄдÁËһϡ£
SELECT
*
from
`
table
`
WHERE
id
>=
(
SELECT
floor
(
RAND
()
*
(
SELECT
MAX
(id)
from
`
table
`)))
ORDER
BY
id LIMIT
1
;
ÕâÏ£¬Ð§ÂÊÓÖÌá¸ßÁË£¬²éѯʱ¼äÖ»ÓÐ0.01Ãë
×îºó£¬ÔÙ°ÑÓï¾äÍêÉÆһϣ¬¼ÓÉÏMIN(id)µÄÅжϡ£ÎÒÔÚ×ʼ²âÊÔµÄʱºò£¬¾ÍÊÇÒòΪûÓмÓÉÏMIN(id)µÄÅжϣ¬½á¹ûÓÐÒ»°ëµÄʱ¼ä×ÜÊDzéѯµ½±í
ÖеÄÇ°Ã漸ÐС£
ÍêÕû²éѯÓï¾äÊÇ£º
SELECT
*
from
`
table
`
WHERE
id
&g
Ïà¹ØÎĵµ£º
MySQL³£ÓÃÃüÁî×ܽá
===MySQL»ù´¡====
mysqlÏÂÔØ: http://www.mysql.com/
mysqld ³£¹æMySQL·þÎñÆ÷
mysqld-opt ÓÅ»¯mysql·þÎñÆ÷,ÌṩһЩ¹¦ÄÜ¿ÉÒÔÍÚ¾ò¸üºÃµÄ¹¦ÄÜ
mysqld-max ÓëmysqldÒ»Ñù,µ«¿ÉÒÔÖ§³Ö¸üÐÂ,¸ü¾ßʵÑéÐÔÖʵŦÄÜ(¸ü²»Îȶ¨)
++°²×°mysql
²Î¼û×Ô´øµÄINSTALL-SOURCEÎļþ
$ ./configure –prefix=/app/m ......
ÒÔÏÂΪOracleºÍMySQLÊý¾Ý¿âµÄһЩ¼òµ¥ÃüÁî¶Ô±È£¬¿´¿´ËüÃÇÖ®¼ä´æÔÚÄÄЩ²îÒì
¡¡¡¡SQL> select to_char(sysdate,'yyyy-mm-dd') from dual;
¡¡¡¡SQL> select to_char(sysdate,'hh24-mi-ss') from dual;
¡¡¡¡mysql> select date_format(now(),'%Y-%m-%d');
¡¡¡¡mysql> select time_format(now(),'%H-%i-%S');
¡¡¡¡ÈÕÆÚº ......
1. Á¬½Ómysql:
mysqlbinmysql -hÖ÷»úµØÖ· -u Óû§Ãû £p Óû§ÃÜÂë
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
mysq ......
¹«Ë¾µÄ·þÎñÆ÷ÊÇCentOS 5.4(Final)°æµÄ£¬½ñÌìÔÚÉÏÃæ°²×°ÁËÒ»»Ømysql5.5£¬¼Ç¼ÈçÏ£º
1¡¢´Óhttp://blog.s135.com/soft/linux/nginx_php/mysql/mysql-5.5.2-m2.tar.gz ÏÂÔØÔ´Âë°²×°°üµ½/usr/local/src
2¡¢tar zxvf mysql-5.5.2-m2.tar.gz ½âѹµ½/usr/local/src/mysql-5.5.2-m2ÏÂ
cd mysql-5.5.2-m2/
&n ......
MySQL Á·Ï°ÊÖ¸å
MySQL ½éÉÜ
MySQL ABÊÇÓÉMySQL´´Ê¼È˺ÍÖ÷Òª¿ª·¢ÈË´´°ìµÄ¹«Ë¾¡£MySQL AB×î³õÊÇÓÉDavid Axmark¡¢Allan
LarssonºÍMichael“Monty
”WideniusÔÚÈðµä´´°ìµÄ¡£
¹«Ë¾ÃûÖеēAB”ÊÇÈðµäÓ ......