{"id":136,"title":"\u89c6\u56fe","good":0,"bad":0,"hit":1960,"created_at":"2014-12-22 17:32:02","content":"

\u89c6\u56fe\uff0c\u662f\u4e00\u5f20\u8868\uff0c\u4f46\u662f\u865a\u62df\u8868\uff01<\/p>

\u662f\u901a\u8fc7\u4e00\u6761\u67e5\u8be2\u8bed\u53e5\u5f97\u5230\u4e00\u4e2a\u5f20\u865a\u62df\u8868\uff01<\/p>

\u56e0\u6b64\uff0c\u8ba4\u4e3a\u89c6\u56fe\uff0c\u5c31\u662f select\u8bed\u53e5\u7684\u7ed3\u679c\uff01\u4e5f\u53ef\u4ee5\u7406\u89e3\u4e3a\u89c6\u56fe\u91cc\u5b58\u50a8\u7684\u662f\u4e00\u6761\u67e5\u8be2sql\u8bed\u53e5<\/p>

 <\/p>

\u8bed\u6cd5\uff1a<\/p>

create view \u89c6\u56fe\u540d\u5b57 AS \u67e5\u8be2\u8bed\u53e5<\/p>

<\/p>

\u6bd4\u5982\uff1a\u67e5\u627e\u73ed\u91cc\u7684\u6700\u9ad8\u6700\u5bcc\u7684\u540c\u5b66\uff1b<\/p>

select * from student where (height,money)=(select max(height),max(money) from student);<\/p>

\u8fd9\u6837\u5199\u6bd4\u8f83\u957f\uff0c\u5982\u679c\u5148\u5efa\u7acb\u4e00\u4e2a\u89c6\u56fe\uff1a<\/p>

create view view_gf as select * from student where (height,money)=(select max(height),max(money) from student);<\/p>

\u90a3\u4e48\u6211\u4eec\u73b0\u5728\u901a\u8fc7\u89c6\u56fe\u67e5\u8be2\u4e00\u6837\u53ef\u4ee5\u5f97\u5230\u76f8\u540c\u7684\u7ed3\u679c\uff1a<\/p>

select * from view_gf;<\/p>

\u770b\uff0c\u8bed\u53e5\u662f\u4e0d\u662f\u53d8\u5f97\u5f88\u7b80\u5355\u4e86\uff1b<\/p>

<\/p>

\u89c6\u56fe\u7684\u4f5c\u7528<\/p>

\u53ef\u89c1\uff0c\u4f7f\u7528\u89c6\u56fe\u7684\u529f\u80fd\u4e4b\u4e00\uff0c\u5c31\u662f\u7b80\u5316\u67e5\u8be2\u7684\u4e1a\u52a1\u903b\u8f91\uff01 <\/p>

\u6ce8\u610f\uff1a\u89c6\u56fe\u5185\u662f\u4e0d\u4fdd\u5b58\u771f\u5b9e\u6570\u636e\u7684\uff01\u89c6\u56fe\u5185\uff0c\u53ea\u6709\u4e00\u6761\u5f62\u6210\u89c6\u56fe\u7684 select \u8bed\u53e5\u800c\u5df2\uff01 <\/p>

\u56e0\u6b64\uff0c\u6bcf\u6b21\u4ece\u89c6\u56fe\u67e5\u8be2\u65f6\uff0c\u90fd\u9700\u8981\u5229\u7528\u89c6\u56fe\uff0c\u518d\u5728\u771f\u5b9e\u7684\u8868\u5185\u5c06\u6570\u636e\u67e5\u8be2\u5230\uff01<\/p>

\u7c7b\u4f3c\u4e00\u4e2a from\u578b\u5b50\u67e5\u8be2\uff01<\/p>

<\/p>

 <\/p>

 <\/p>

\u529f\u80fd\u4e4b\u4e8c\uff1a\u9690\u85cf\u771f\u5b9e\u7684\u8868\u7ed3\u6784\uff01 \uff08\u5728\u89c6\u56fe\u4e2d\u5c06\u5b57\u6bb5\u7528as\u522b\u540d\u4ee3\u66ff\uff0c\u8fbe\u5230\u9690\u85cf\u771f\u5b9e\u5b57\u6bb5\u540d\u7684\u4f5c\u7528\uff09<\/p>

\u4ece\u800c\u53d6\u5f97\u66f4\u5927\u7684\u517c\u5bb9\u6027 <\/p>

\u603b\u7ed3\u4f5c\u7528\uff1a1,\u7b80\u5316\u903b\u8f91\uff0c2,\u56e0\u6b64\u771f\u5b9e\u7684\u7ed3\u6784\uff08\u517c\u5bb9\u6027\uff0c\u9650\u5236\u7528\u6237\u7684\u5904\u7406\uff09<\/p>

 <\/p>

 <\/p>

\u89c6\u56fe\u7b97\u6cd5\uff0c\u6267\u884c\u65b9\u5f0f<\/p>

\u4f8b\u5b50\uff1a\u53d6\u5f97\u6bcf\u4e2a\u73ed\u7ea7\u6700\u9ad8\u7684\u5b66\u751f\u4fe1\u606f(\u5f53\u540c\u73ed\u6709\u76f8\u540c\u8eab\u9ad8\u4e14\u5747\u4e3a\u6700\u9ad8\u65f6\uff09<\/p>

\u4f7f\u7528 from\u578b\u5b50\u67e5\u8be2\uff0c\u53ef\u4ee5\uff0c\u4f46\u662f\u4f7f\u7528\u540c\u6837\u903b\u8f91\u7684\u89c6\u56fe\u4e0d\u884c\uff01<\/p>

\u7528\u5b50\u67e5\u8be2\uff1a\u53ef\u4ee5\u67e5\u5230\u540c\u73ed\u6700\u9ad8\u4e14\u8eab\u9ad8\u4e00\u6837\u7684\u591a\u540d\u540c\u5b66<\/p>

select * from student where height in(select max(height) as height from student group by classid);<\/p>

\u4f46\u662f\u7528\u5f53\u7528\u6b64\u5b50\u67e5\u8be2\u5efa\u7acb\u89c6\u56fe\u540e\uff1a<\/p>

create view view_height as select * from student where height in(select max(height) as height from student group by classid);<\/p>

\u901a\u8fc7\u89c6\u56fe\u67e5\u8be2\u5f97\u5230\u76f8\u540c\u7ed3\u679c\uff1a<\/p>

select * from view_height;<\/p>

<\/p>

\u4f46\u662f\u5982\u679c\u89c6\u56fe\u5efa\u7acb\u4e0d\u9002\u5f53\u65f6\uff0c\u53ef\u80fd\u51fa\u73b0\u91cd\u590d\u7684\u503c\uff0c\u6709\u65f6\u5019\u4f1a\u51fa\u73b0\u67e5\u8be2\u7ed3\u679c\u4e0d\u5339\u914d\uff1a<\/p>

 <\/p>

\u89c6\u56fe\u5176\u5b9e\u4e00\u5171\u6709\u4e09\u79cd\u6267\u884c\u65b9\u5f0f\uff1a<\/p>

merge\uff0c\u5408\u5e76<\/p>

temptable\uff0c\u4e34\u65f6\u8868<\/p>

undefined\uff0c\u672a\u5b9a\u4e49\uff0c\u5c31\u662f\u9ed8\u8ba4\u7684\uff0cmysql\u81ea\u5df1\u51b3\u5b9a\u7b97\u6cd5\uff08\u4ecemerge\uff0c\u548ctemptable\u5185\u9009\u62e9\uff09\uff01<\/p>

 <\/p>

\u5178\u578b\u7684\u90fd\u662f\u9009\u62e9\u7684merge\u7684\uff1a<\/p>

 <\/p>

\u5982\u4f55\u89e3\u51b3\uff1f<\/p>

\u53ef\u4ee5\u9009\u62e9\u51b3\u5b9a\u89c6\u56fe\u7684\u7b97\u6cd5\uff01\u5728\u521b\u5efa\u89c6\u56fe\u65f6\uff0c\u6307\u5b9a\u3002<\/p>

ALGORITHM=temptable\u5373\u53ef<\/p>

<\/p>

algorithm<\/p>

\u7528\u5230\u6bd4\u8f83\u5c11\uff01<\/p>

<\/p>"}