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

mysql²Ù×÷ Left join , Right Join, Inner Join


Ò».ÏÈ¿´Ò»Ð©×î¼òµ¥µÄÀý×Ó
Àý×Ó
Table A
aid   adate
1      a1
2      a2
3      a3
TableB
bid bdate
1    b1
2   b2
4    b4
Á½¸ö±ía,bÏàÁ¬½Ó,Ҫȡ³öidÏàͬµÄ×Ö¶Î
select * from a inner join
b on a.aid = b.bidÕâÊǽöÈ¡³öÆ¥ÅäµÄÊý¾Ý.
´ËʱµÄÈ¡³öµÄÊÇ:
1 a1 b1
2 a2 b2
ÄÇôleft join Ö¸:
select * from a left join
b on
a.aid = b.bid
È¡³öa±íËùÓÐÊý¾Ý,ÄÃbµÄÊý¾ÝÓëa±È½Ï,ÏàͬµÄÈ¡³ö,²»Í¬µÄbÈ¡¿Õֵȡ³ö
´ËʱµÄÈ¡³öµÄÊÇ:
1 a1 b1
2 a2 b2
3 a3 ¿Õ×Ö·û
ͬÑùµÄÒ²ÓÐright join
 
select * from a right join
b on
a.aid = b.bid
È¡³öb±íËùÓÐÊý¾Ý,ÄÃaµÄÊý¾ÝÓëb±È½Ï,ÏàͬµÄÈ¡³ö,²»Í¬µÄaÈ¡¿Õֵȡ³ö
´ËʱµÄÈ¡³öµÄÊÇ:
1 a1 b1
2 a2 b2
4 ¿Õ×Ö·û b4
×¢:
¶¼ÊÇÔÚonµÄÌõ¼þÏÂ
¶þ. left join/right join/inner join²Ù×÷ÑÝʾ
±íA¼Ç¼ÈçÏ£º
aID        aNum
1           a20050111
2           a20050112
3           a20050113
4          a20050114
5           a20050115
±íB¼Ç¼ÈçÏÂ:
bID        bName
1            2006032401
2            2006032402
3           2006032403
4           2006032404
8           2006032408
ʵÑéÈçÏÂ:
1.    left join
sqlÓï¾äÈçÏÂ:
SELECT

*

from
A
LEFT

JOIN
B
ON
A.aID
=
B.bID
½á¹ûÈçÏÂ:
aID        aNum     &


Ïà¹ØÎĵµ£º

MySQL²éѯµÄÐÔÄÜÓÅ»¯

²éѯÊÇÊý¾Ý¿â¼¼ÊõÖÐ×î³£ÓõIJÙ×÷¡£²éѯ²Ù×÷µÄ¹ý³Ì±È½Ï¼òµ¥£¬Ê×ÏÈ´Ó¿Í»§¶Ë·¢³ö²éѯµÄSQLÓï¾ä£¬Êý¾Ý¿â·þÎñ¶ËÔÚ½ÓÊÕµ½Óɿͻ§¶Ë·¢À´µÄSQLÓï¾äºó£¬Ö´ÐÐÕâÌõSQLÓï¾ä£¬È»ºó½«²éѯµ½µÄ½á¹û·µ»Ø¸ø¿Í»§¶Ë¡£ËäÈ»¹ý³ÌºÜ¼òµ¥£¬µ«²»Í¬µÄ²éѯ·½Ê½ºÍÊý¾Ý¿âÉèÖ㬶ԲéѯµÄÐÔÄܽ«»áÓкÜÔÚµÄÓ°Ïì¡£
Òò´Ë£¬±¾ÎľÍÔÚMySQLÖг£ÓõIJéѯÓÅ»¯¼¼Êõ½ø ......

ʹÓà MySQL Workbench ¿ÉÊÓ»¯µÄÉè¼Æ MySQL Êý¾Ý¿â

MySQL Workbench ÊÇ MySQL ×î½üÊͷŵĿÉÊÓÊý¾Ý¿âÉè¼Æ¹¤¾ß¡£Õâ¸ö¹¤¾ßÊÇÉè¼Æ MySQL Êý¾Ý¿âµÄרÓù¤¾ß¡£
ÄãÔÚ MySQL Workbench Öн¨Á¢µÄ±»³ÆÖ®ÎªÎïÀíÊý¾ÝÄ£ÐÍ¡£Ò»¸öÎïÀíÊý¾ÝÄ£ÐÍÊÇÕë¶ÔÒ»¸öÌØ¶¨ RDBMS ²úÆ·µÄÊý¾ÝÄ£ÐÍ£»±¾ÎÄÖеÄÄ£Ðͽ«¾ßÓÐһЩ MySQL µÄ¶ÀÌØ¹æ·¶¡£ÎÒÃÇ¿ÉÒÔʹÓÃËüÉú³É£¨forward-engineer£©Êý¾Ý¿â¶ÔÏ󣬳ýÁ˰üº¬± ......

mysql Êý¾Ý´æ´¢×ܽá

ÓÉÓÚ×î½üÒ»Ö±ÔÚÁ˽âmysql¡£¸÷ÖÖ±íÀàÐ͵ÄÊý¾Ý´æ´¢ÒÔ¼°Ïà¹ØÏÞÖÆ¾ÍÊDZØÐëÁ˽âµÄ·½ÃæÁË¡£
×Ô¼ºµÄ·þÎñÆ÷»·¾³£ºOS Cent OS ext3£¬memory 4G£¬ disk 2T block size 4K¡£
¾­µ÷²é£¬linuxÏÂÎļþ×î´óÊÇ´æÔÚÏÞÖÆµÄ¡£È¥googleÉÏËÑÁËËÑ£¬´ó¼Ò˵·¨²»Ò»£¬×îÖÕ×Ô¼º»¹ÊÇÕÒµ½±È½Ï¹Ù·½µÄ˵¡£Ïê¼ûhttp://en.wikipedia.org/wiki/Ext3 ËùÒÔ× ......

Mysql³£ÓÃÃüÁî½Å±¾

Mysql³£ÓÃÃüÁî½Å±¾
µÚÒ»ÕС¢mysql·þÎñµÄÆô¶¯ºÍÍ£Ö¹
net stop mysql
net start mysql
µÚ¶þÕС¢µÇ½mysql
Óï·¨ÊÇ mysql -hÖ÷»ú -uÓû§Ãû -pÃØÃÜ
Àý×ÓÊÇ mysql -hlocalhost -uroot -p123456
Ҫȷ¶¨mysql°²×°Ê±ºò¹´Ñ¡ÁË¿ÉÒÔÔ¶³ÌÁ´½Ó¡£Èç¹ûµÇ½±¾µØ¼ÆËã»ú£¬-h¿ÉÒÔÊ¡ÂÔ£¬¼üÈëÃüÁîmysql -uroot -p£¬ »Ø³µºóÌáʾÄãÊäÈëÃÜÂ룬 ......

Mysql ʱ¼äº¯Êý»ã×Ü

 Ò»¡¢MySQL »ñµÃµ±Ç°ÈÕÆÚʱ¼ä º¯Êý
1.1 »ñµÃµ±Ç°ÈÕÆÚ+ʱ¼ä£¨date + time£©º¯Êý£ºnow()
mysql> select now();
+---------------------+
| now() |
+---------------------+
| 2008-08-08 22:20:46 |
+---------------------+
³ýÁË now() º¯ÊýÄÜ»ñµÃµ±Ç°µÄÈÕÆÚʱ¼äÍ⣬MySQL Öл¹ÓÐÏÂÃæµÄº¯Êý£º
current_tim ......
© 2009 ej38.com All Rights Reserved. ¹ØÓÚE½¡ÍøÁªÏµÎÒÃÇ | Õ¾µãµØÍ¼ | ¸ÓICP±¸09004571ºÅ