mysql ÐÐתÁÐÎÊÌâ
Õ⼸ÌìËù×÷µÄ¹¤×÷Éæ¼°µ½Êý¾Ý¿âÐÐתÁеÄÎÊÌâ
¼Ç¼һϳöÏֵĴíÎó£¬ÒÔÃâÒÔºóÔÙ·¸
¾ÙÍøÉÏ×îͨË×µÄÀý×Ó°É
Name Subject Result
ÕÅÈý ÓïÎÄ 80
ÕÅÈý Êýѧ 90
ÕÅÈý ÎïÀí 85
ÀîËÄ ÓïÎÄ 85
ÀîËÄ Êýѧ 92
ÀîËÄ ÎïÀí 82
ÏëÒªµÄ½á¹û
ÐÕÃû ÓïÎÄ Êýѧ ÎïÀí
ÕÅÈý 80 90 85
ÀîËÄ 85 92 82
ÕýÈ·µÄд·¨
select name as ÐÕÃû,
max
(case when subject='ÓïÎÄ' then result end) as ÓïÎÄ,
max
(case when subject='Êýѧ' then result end) as Êýѧ,
max
(case when subject='ÎïÀí' then result end) as ÎïÀí
from T1 group by
name
×ʼдµÄʱºò²»ÖªµÀmax
º¯ÊýÓÐʲôÓÃ
¶øÇÒҲûÓмÓ
group by
×îºóµÄ½á¹ûÊÇ
ÐÕÃû ÓïÎÄ Êýѧ ÎïÀí
ÕÅÈý 80
ÕÅÈý 90
ÕÅÈý 85
ÀîËÄ 85
ÀîËÄ 92
ÀîËÄ 82
·¢ÏÖ½á¹û²»¶Ô£¬È»ºó¼ÓÁË
group byÓï¾ä
½á¹ûÊÇ
ÕÅÈý 80
ÀîËÄ 85
Ïà¹ØÎĵµ£º
integer »òÕß int
int »òÕß java.lang.Integer
INTEGER
4 ×Ö½Ú
long
long Long
BIGINT
8 ×Ö½Ú
short
short Short
SMALLINT
2 ×Ö½Ú
byte
byte Byte
TINYINT
1 ×Ö½Ú
float
float Float
FLOAT
4 ×Ö½Ú
double
double Double
DOUBLE
8 ×Ö½Ú
b ......
¡¡ÍøÉÏÓкܶàµÄÎÄÕ½ÌÔõôÅäÖÃMySQL·þÎñÆ÷£¬µ«¿¼Âǵ½·þÎñÆ÷Ó²¼þÅäÖõIJ»Í¬£¬¾ßÌåÓ¦ÓõIJî±ð£¬ÄÇЩÎÄÕµÄ×ö·¨Ö»ÄÜ×÷Ϊ³õ²½ÉèÖòο¼£¬ÎÒÃÇÐèÒª¸ù¾Ý×Ô¼ºµÄÇé¿ö½øÐÐÅäÖÃÓÅ»¯£¬ºÃµÄ×ö·¨ÊÇMySQL·þÎñÆ÷Îȶ¨ÔËÐÐÁËÒ»¶Îʱ¼äºóÔËÐУ¬¸ù¾Ý·þÎñÆ÷µÄ”״̬”½øÐÐÓÅ»¯¡£
mysql> show global status;
¡¡¡¡¿ÉÒÔÁгöMySQL·þÎ ......
ÏÂÎç¿´ÁËÒ»¶ÎPHP100µÄÊÓÆµ¡£
Ò²ËãÓеãÊÕ»ñ¡£
ÀïÃæµÄÒ»¶Î×ÔдµÄfindallµÄSQLº¯Êý£º
public function findall($table) {
$this->query("SELECT * from $table");
}
ÔÀ´Ö»ÊÇÕâô¼òµ¥£¬¸Õ»¹ÔÚ˼¿¼¡£
ʹÓÃÁËTAB¼üÉÏÃæµÄ¶ÙºÅÀ´ÐÞÊÎMYSQLÀïµÄ×Ö¶ÎÃû£¬È磺
UPDATE tablename SET `fieldname`='values' wh ......
ÔÚ֮ǰµÄÎÄÕÂÀÎÒÒѾÌá¹ýÈçºÎ½â¾öJSPÖÐÂÒÂëÎÊÌ⣨½â¾ötomcatÏÂÖÐÎÄÂÒÂëÎÊÌâ £©£¬ÆäÖÐÒ²Ïêϸ½â˵ÁËMYSQLÂÒÂëÎÊÌ⣬ÏàÐÅͨ¹ýÀïÃæµÄ°ì·¨£¬¿Ï¶¨¶¼ÒѾ½â¾öÁËJSPÀïµÄÂÒÂëÎÊÌ⣬²»¹ý»¹ÊÇÓÐЩÈ˵ÄMYSQLÂÒÂëÎÊÌâûÓеõ½½â¾ö£¬°üÀ¨ÎÒ×Ô¼º£¬ËùÒÔÓÖÕÒÁËһЩ×ÊÁÏ£¬Ï£ÍûÕâ´ÎÄÜÍêÈ«½â¾öMYSQLÊý¾Ý¿âµÄÂÒÂëÎÊÌâ¡£
......
Explain MySQL architecture
. - The front layer
takes care of network connections and security authentications, the
middle layer does the SQL query parsing, and then the query is handled
off to the storage engine. A storage engine could be either a default
one supp ......