in\u662f\u628a\u5916\u8868\u548c\u5185\u8868\u4f5chash \u8fde\u63a5\uff0c\u800cexists \u662f\u5bf9\u5916\u8868\u4f5cloop \u5faa\u73af\uff0c\u6bcf\u6b21loop \u5faa\u73af\u518d\u5bf9\u5185\u8868\u8fdb\u884c\u67e5\u8be2\u3002
\n\u4e00\u76f4\u4ee5\u6765\u8ba4\u4e3aexists \u6bd4in \u6548\u7387\u9ad8\u7684\u8bf4\u6cd5\u662f\u4e0d\u51c6\u786e\u7684\u3002\u5982\u679c\u67e5\u8be2\u7684\u4e24\u4e2a\u8868\u5927\u5c0f\u76f8\u5f53\uff0c\u90a3\u4e48\u7528in \u548cexists \u5dee\u522b\u4e0d\u5927\u3002<\/p>\n
<\/p>\n
\u5982\u679c\u4e24\u4e2a\u8868\u4e2d\u4e00\u4e2a\u8f83\u5c0f\uff0c\u4e00\u4e2a\u662f\u5927\u8868\uff0c\u5219\u5b50\u67e5\u8be2\u8868\u5927\u7684\u7528exists\uff0c\u5b50\u67e5\u8be2\u8868\u5c0f\u7684\u7528in\uff1a
\n\u4f8b\u5982\uff1a
\n\u8868A\uff08\u5c0f\u8868\uff09\uff0c\u8868B\uff08\u5927\u8868\uff091\uff1a<\/p>\n
select * from A where cc in (select cc from B)<\/p>\n
\u6548\u7387\u4f4e\uff0c\u7528\u5230\u4e86A \u8868\u4e0acc \u5217\u7684\u7d22\u5f15\uff1b<\/p>\n
select * from A where exists(select cc from B where cc=A.cc)<\/p>\n
\u6548\u7387\u9ad8\uff0c\u7528\u5230\u4e86B \u8868\u4e0acc \u5217\u7684\u7d22\u5f15\u3002<\/p>\n
\u76f8\u53cd\u76842\uff1a<\/p>\n
select * from B where cc in (select cc from A)<\/p>\n
\u6548\u7387\u9ad8\uff0c\u7528\u5230\u4e86B \u8868\u4e0acc \u5217\u7684\u7d22\u5f15\uff1b<\/p>\n
select * from B where exists(select cc from A where cc=B.cc)<\/p>\n
\u6548\u7387\u4f4e\uff0c\u7528\u5230\u4e86A \u8868\u4e0acc \u5217\u7684\u7d22\u5f15\u3002<\/p>\n
not in \u548cnot exists
\n\u5982\u679c\u67e5\u8be2\u8bed\u53e5\u4f7f\u7528\u4e86not in \u90a3\u4e48\u5185\u5916\u8868\u90fd\u8fdb\u884c\u5168\u8868\u626b\u63cf\uff0c\u6ca1\u6709\u7528\u5230\u7d22\u5f15\uff1b
\n\u800cnot extsts \u7684\u5b50\u67e5\u8be2\u4f9d\u7136\u80fd\u7528\u5230\u8868\u4e0a\u7684\u7d22\u5f15\u3002\u6240\u4ee5\u65e0\u8bba\u90a3\u4e2a\u8868\u5927\uff0c\u7528not exists \u90fd\u6bd4not in \u8981\u5feb\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
in\u662f\u628a\u5916\u8868\u548c\u5185\u8868\u4f5chash \u8fde\u63a5\uff0c\u800cexists \u662f\u5bf9\u5916\u8868\u4f5cloop \u5faa\u73af\uff0c\u6bcf\u6b21loop \u5faa\u73af\u518d\u5bf9… \u7ee7\u7eed\u9605\u8bfb mysql \u4f18\u5316\u306e in \u548cexists<\/span><\/i><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[2],"tags":[],"_links":{"self":[{"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=\/wp\/v2\/posts\/82"}],"collection":[{"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=82"}],"version-history":[{"count":1,"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=\/wp\/v2\/posts\/82\/revisions"}],"predecessor-version":[{"id":83,"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=\/wp\/v2\/posts\/82\/revisions\/83"}],"wp:attachment":[{"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=82"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=82"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.anthonylee.cn\/myblog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=82"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}