MySQL³£¼û×Ö·û´®º¯Êýѧϰ
1.reverse(str)º¯Êý: ·µ»Øµßµ¹×Ö·û˳ÐòµÄ×Ö·û´®str, ¸Ãº¯Êý¶Ô¶à×Ö½Ú¿É¿¿µÄ.
mysql> select * from user;
+----+------------------+
| id | name |
+----+------------------+
| 1 | test |
| 2 | test2 |
| 3 | abc cde aa bb_cc |
| 4 | abc |
+----+------------------+
4 rows in set (0.00 sec)
mysql> select id,reverse(name) name from user;
+----+------------------+
| id | name |
+----+------------------+
| 1 | tset |
| 2 | 2tset |
| 3 | cc_bb aa edc cba |
| 4 | cba |
+----+------------------+
4 rows in set (0.01 sec)
2.substring(str,start,length)º¯Êý£º·µ»Østr×Ö·û´®ÖдӿªÊ¼Î»ÖÃstart¿ªÊ¼³¤¶ÈΪlengthµÄ×Ö·û´®¡£
mysql> select id,substring(name,1,2) name from user;
+----+------+
| id | name |
+----+------+
| 1 | te |
| 2 | te |
| 3 | ab |
| 4 | ab |
+----+------+
4 rows in set (0.00 sec)
×¢Ò⣬µÚÒ»¸ö×Ö·ûµÄλÖÃΪ1£¬¶ø²»ÊÇ0.Èç¹ûÓÃsubstring(name,0,2)£¬»á·µ»Ønull.
mysql> select id,substring(name,0,2) name from user;
+----+------+
| id | name |
+----+------+
| 1 | NULL |
| 2 | NULL |
| 3 | NULL |
| 4 | NULL |
+----+------+
4 rows in set (0.00 sec)
3.substring_index(str,delim,n)º¯Êý:·µ»Ø×Ö·û´®strÖеÚn´Î³öÏÖdelim×Ö·û֮ǰµÄËùÓÐ×Ö·û£¬Èç¹ûnΪ¸ºÊý£¬Ôò±íʾ´Ó·´·½Ïò¿ªÊ¼¼ÆÊý¡£
mysql> select * from user;
+----+----------------------------
Ïà¹ØÎĵµ£º
mysql³£ÓÃÃüÁî
¹Ø±ÕÊý¾Ý¿â
/data01/mysql/bin/mysqladmin -p shutdown
µ¼³öÊý¾Ý¿â
/usr/local/mysql/bin/mysqldump -opt -uroot -p -h10.15.0.45 bbsdb > 20070918.bbsdb.sql
µ¼ÈëÊý¾Ý¿â
/usr/local/mysql/bin/mysql target_db_name < backup-file.sql
ÏÞÖÆÖ»ÓÐÄÚ²¿ip¿ÉÒÔÁ´½Ó
/u ......
»°ËµÖ®Ç°ÓÃphpдµÄÒ»¸öͳ¼ÆÅܵúúõģ¬Í»È»Ò»Ìì²»³öÊý¾ÝÁË£¬×·ÆäÔÒò³öÔÚsqlÓï¾äÉÏ£¬ÓÉÓÚÊý¾ÝÁ¿Ôö´ó¼ÓÉÏ·þÎñÆ÷ÀϾɣ¬ÔËÐÐsqlÓï¾äµÄʱºò³öÏÖÄÚ´æ²»×ãµÄÌáʾ£¬Ëì¾ö¶¨ÓÅ»¯sqlÓï¾äʹÆä²»²úÉúÁÙʱ±í¡£ÐèÇóÇåÎú£¬ÏÂÃæ¾ÙÀý˵Ã÷£º
ÔsqlÓï¾ä£º
SELECT COUNT( DISTINCT md5 ) from active AS a
......
PERCONA PERFORMANCE CONFERENCE 2009ÉÏ£¬À´×ÔÑÅ»¢µÄ¼¸Î»¹¤³Ìʦ´øÀ´ÁËһƪ”Efficient Pagination Using MySQL“µÄ±¨¸æ£¬ÓкܶàÁÁµã£¬±¾ÎÄÊÇÔÚÔÎÄ»ù´¡ÉϵĽøÒ»²½ÑÓÉì¡£
Ê×ÏÈ¿´Ò»Ï·ÖÒ³µÄ»ù±¾ÔÀí£º
mysql> explain SELECT * from message ORDER BY id DESC LIMIT 10000, 20\G
***************** 1. row ** ......
´´½¨Êý¾Ý¿â£ºcreate database Êý¾Ý¿âÃû;
´´½¨±í£ºcreate table ±íÃû £¨ ÁÐÃû Êý¾ÝÀàÐÍ not null... £©;
²é¿´ÏµÍ³ÖÐËùÓеÄÊý¾Ý¿â£ºshow databases;
Ñ¡ÔñÒªÓ¦ÓõÄÊý¾Ý¿â£ºuse Êý¾Ý¿âÃû;
²é¿´Ä³¸öÊý¾Ý¿âϵÄËùÓÐ±í£ºshow tables;
²é¿´±í½á¹¹£ºdesc(describe) ±íÃû;
ÖØÃüÃû±íÃû£ºalter table ±íÃû rename as бíÃû
¸ ......
Mysql£¬SqlServer£¬OracleÖ÷¼ü×Ô¶¯Ôö³¤µÄÉèÖÃ
1¡¢°ÑÖ÷¼ü¶¨ÒåΪ×Ô¶¯Ôö³¤±êʶ·ûÀàÐÍ
ÔÚmysqlÖУ¬Èç¹û°Ñ±íµÄÖ÷¼üÉèΪauto_incrementÀàÐÍ£¬Êý¾Ý¿â¾Í»á×Ô¶¯ÎªÖ÷¼ü¸³Öµ¡£ÀýÈ磺
create table customers(id int auto_increment primary key not null, name varchar(15));
insert into customers(name) values("name1"),("nam ......