SQL²éѯÓÅ»¯,×¢ÒâwhereÌõ¼þµÄ˳Ðò
×÷Õß:ÂÞ´ú¾ù ldj_work#126.com ×ªÔØÇë±£³ÖÍêÕûÐÔ
1.²âÊÔ±í
employee
¹ÍÔ±id ²¿ÃÅid н½ð
emp_id dept_id salary
01 01 1050
02 01 2000
ok,ÎÒÃÇÒª²éÕÒ²¿ÃÅ01ÏÂ,н½ð¸ßÓÚ1000µÄ¹ÍÔ±
2.ÔÔò¼°Á½¸öSQLµÄ¶Ô±È
ÔÔò,¶àÊýÊý¾Ý¿â¶¼ÊÇ´Ó ×óµ½ÓÒµÄ˳Ðò´¦ÀíÌõ¼þ,°ÑÄܹýÂ˸ü¶àÊý¾ÝµÄÌõ¼þ·ÅÔÚÇ°Ãæ,¹ýÂËÉÙµÄÌõ¼þ·ÅºóÃæ
SQL1: select * from employee
where salary >1000 --Ìõ¼þ1,¹ýÂ˵ÄÊý¾Ý½ÏÉÙ
and dept_id='01' --Ìõ¼þ2,¹ýÂ˵ÄÊý¾Ý±ÈÌõ¼þ1¶à
ÉÏÃæµÄSQL¾Í²»·ûºÏÎÒÃǵÄÔÔòÁË,Ó¦¸Ã°Ñ¹ýÂËÊý¾Ý¸ü¶àµÄÌõ¼þ·ÅÔÚÇ°Ãæ,Òò´Ë¸ÄΪÏÂÃæÕâÑù¸üºÃ
select * from employee
where dept_id='01' --¹ýÂ˸ü¶àÊý¾ÝµÄÌõ¼þ·ÅÔÚÇ°Ãæ
and salary > 1000
Ïà¹ØÎĵµ£º
ÉÏÖÜÒ»java µÄʧÀûÁË£¬ËäÈ»»¹Ã»Õýʽ¿ªÕâÃſΣ¬µ«ÎÒÒ²×ÔѧÁ˰ëÄ꣬Õâ´ÎµÄʧÀûÈÃÎÒÉî¿ÌÈÏʶÁË×Ô¼ºËù´æÔڵIJ»×㡣ΪÒÔºóѧϰÁôÏÂÁ˱¦¹óµÄ¾Ñé¡£Ê컰˵£º¡°²»È뻢Ѩ£¬Ñɵû¢×Ó¡±¡£
ºóÌ죬ÎÒÒªÔÙÒ»´ÎÈ¥±±´ó¡£Õâ´Î¿¼SQL SERVER2000 £¬Í¬Ñù£¬ÕâÃÅ»¹Ã»Ñ§Í꣬Æäʵ£¬ÊǸտªÊ¼Ñ§¡£Ñ§µ½Á˵ÚÈýÕ¹ØÏµÄ£Ê½Éè¼ÆÔÀí £¬ ËäȻûÓбØÊ¤µÄÐÅÐÄ ......
SQL INNER JOIN ¹Ø¼ü×Ö
SQL INNER JOIN ¹Ø¼ü×Ö
ÔÚ±íÖдæÔÚÖÁÉÙÒ»¸öÆ¥Åäʱ£¬INNER JOIN ¹Ø¼ü×Ö·µ»ØÐС£
INNER JOIN ¹Ø¼ü×ÖÓï·¨
SELECT column_name(s)
from table_name1
INNER JOIN table_name2
ON table_name1.column_name=table_name2.column_name
×¢ÊÍ£ºINNER JOIN Óë JOIN ÊÇÏàͬµÄ¡£
ÔʼµÄ±í (ÓÃÔÚÀ ......
SQL JOIN
SQL join ÓÃÓÚ¸ù¾ÝÁ½¸ö»ò¶à¸ö±íÖеÄÁÐÖ®¼äµÄ¹ØÏµ£¬´ÓÕâЩ±íÖвéѯÊý¾Ý¡£
Join ºÍ Key
ÓÐʱΪÁ˵õ½ÍêÕûµÄ½á¹û£¬ÎÒÃÇÐèÒª´ÓÁ½¸ö»ò¸ü¶àµÄ±íÖлñÈ¡½á¹û¡£ÎÒÃǾÍÐèÒªÖ´ÐÐ join¡£
Êý¾Ý¿âÖеıí¿Éͨ¹ý¼ü½«±Ë´ËÁªÏµÆðÀ´¡£Ö÷¼ü£¨Primary Key£©ÊÇÒ»¸öÁУ¬ÔÚÕâ¸öÁÐÖеÄÿһÐеÄÖµ¶¼ÊÇΨһµÄ¡£ÔÚ±íÖУ¬Ã¿¸öÖ÷¼üµÄ ......
Ò»¡¢NATURAL JOIN£¨×ÔÈ»Á¬½Ó£©
Á½Õűíͨ¹ýNATURAL JOINÁ¬½ÓµÄʱºò£¬Ï൱ÓÚÓиöÒþº¬µÄWHERE×Ӿ䣬¶ÔÁ½ÕűíÖÐͬÃûµÄ¶ÔÓ¦ÁÐÏà±È½Ï¿´ÊÇ·ñÏàµÈ¡£
¶þ¡¢CROSS JOIN£¨´´½¨µÑ¿¨¶û»ý£©
¶ÔÁ½Õűíͨ¹ý½»²æÁªºÏ²úÉúµÚÈýÕÅ·µ»Ø½á¹û¼¯µÄ±í¡£Ï൱ÓÚÆÕͨµÄÁ¬½Ó¡£
Èý¡¢INNER JOIN£ ......
1¡¢Ã»ÓÐË÷Òý»òÕßûÓÐÓõ½Ë÷Òý(ÕâÊDzéѯÂý×î³£¼ûµÄÎÊÌ⣬ÊdzÌÐòÉè¼ÆµÄȱÏÝ)
¡¡¡¡2¡¢I/OÍÌÍÂÁ¿Ð¡£¬ÐγÉÁËÆ¿¾±Ð§Ó¦¡£
¡¡¡¡3¡¢Ã»Óд´½¨¼ÆËãÁе¼Ö²éѯ²»ÓÅ»¯¡£
¡¡¡¡4¡¢ÄÚ´æ²»×ã
¡¡¡¡5¡¢ÍøÂçËÙ¶ÈÂý
¡¡¡¡6¡¢²éѯ³öµÄÊý¾ÝÁ¿¹ý´ó(¿ÉÒÔ²ÉÓöà´Î²éѯ£¬ÆäËûµÄ·½·¨½µµÍÊý¾ÝÁ¿)
¡¡¡¡7¡¢Ëø»òÕßËÀËø(ÕâÒ²ÊDzéѯÂý×î³£¼ûµÄÎÊÌ⣠......