{"id":4366,"date":"2013-03-16T01:01:56","date_gmt":"2013-03-15T17:01:56","guid":{"rendered":"http:\/\/wp.chunhsin.idv.tw\/?p=4366"},"modified":"2013-03-16T01:03:46","modified_gmt":"2013-03-15T17:03:46","slug":"%e6%9f%a5%e8%a9%a2%e6%a2%9d%e4%bb%b6%e7%82%banull%e6%99%82%e8%b7%91%e4%b8%8d%e5%87%ba%e6%9d%b1%e8%a5%bf","status":"publish","type":"post","link":"https:\/\/wp.chunhsin.idv.tw\/?p=4366","title":{"rendered":"\u67e5\u8a62\u689d\u4ef6\u70banull\u6642\u8dd1\u4e0d\u51fa\u6771\u897f"},"content":{"rendered":"<p><strong>select * from SOME_TABLE where colA &lt;&gt; &#8216;3&#8217;<\/strong><\/p>\n<p>\u4e0a\u8ff0\u689d\u4ef6\u6703\u7be9\u9078\u51fa<strong>colA<\/strong>\u6b04\u4f4d\u4e0d\u7b49\u65bc3\u7684\u6240\u6709\u8a18\u9304\u3002\u518d\u6bd4\u5c0d\u4e0b\u5217\u8a9e\u6cd5\uff1a<\/p>\n<p><strong>select * from SOME_TABLE where colA &lt;&gt; null<\/strong><\/p>\n<p>\u6b64\u8a9e\u6cd5\u8dd1\u4e0d\u51fa\u4efb\u4f55\u8a18\u9304\uff0c\u5373\u4f7f\u7684\u78ba\u5b58\u5728\u5176\u4ed6<strong>colA<\/strong>\u6b04\u4f4d\u975enull\u7684\u8a18\u9304\u3002<!--more--><\/p>\n<p>\u5be6\u969b\u8981\u5224\u65b7\u67d0\u6b04\u4f4d\u662f\u5426\u70ba\u7a7a\u503c\u6642\uff0c\u61c9\u7528<strong>colA is null<\/strong>\uff0c\u5224\u65b7\u975e\u7a7a\u503c\u6642\u61c9\u4f7f\u7528c<strong>olA is not null<\/strong>\uff0c\u800c\u975e\u4f7f\u7528=\u6216&lt;&gt;\u6216!=\u3002<\/p>\n<p>\u800c\u5982\u679c\u67d0\u6b04\u4f4d\u7684\u503c\u8981\u4ee5\u5b50\u67e5\u8a62\u4f86\u5224\u65b7\u6642\uff0c\u901a\u5e38\u662f\u9019\u9ebc\u5beb\u7684\uff1a<\/p>\n<p><strong>select * from SOME_TABLE where colA = (select colB from SOME_TABLE where colC=&#8217;eval&#8217;)<\/strong><\/p>\n<p>\u4f46\u5b50\u67e5\u8a62\u4e0d\u4e00\u5b9a\u67e5\u5f97\u5230<strong>colB<\/strong>\uff0c\u5f88\u53ef\u80fd\u8fd4\u56de<strong>null<\/strong>\uff0c\u6b64\u6642\u5c31\u5982\u540c\u524d\u8ff0\u4f7f\u7528=\u6bd4\u5c0d\u6b04\u4f4d\u6642\uff0c\u9047\u5230null\u5c31\u5b8c\u5168\u6bd4\u4e0d\u51fa\u8cc7\u6599\u3002\u5c31\u9019\u500b\u8a9e\u6cd5\u53ef\u80fd\u9084\u770b\u4e0d\u51fa\u4f86\u5dee\u5225\uff0c\u518d\u770b\u4e0b\u4e00\u500b\u4f8b\u5b50\uff1a<\/p>\n<p><strong>select * from SOME_TABLE where colA != (select colB from SOME_TABLE where colC=&#8217;eval&#8217;)<\/strong><\/p>\n<p>\u9019\u500b\u8a9e\u6cd5\u662f\u8981\u627e<strong>colA<\/strong>\u503c\u4e0d\u7b49\u65bc\u5728<strong>colC<\/strong>\u503c\u70ba&#8217;eval&#8217;\u6642\u7684<strong>colB<\/strong>\u503c\u3002\u5047\u8a2d<strong>SOME_TABLE<\/strong>\u7684\u78ba\u5b58\u5728\u5f88\u591a\u8a18\u9304\uff0c\u4f46\u6c92\u6709\u4e00\u500b<strong>colC<\/strong>\u6b04\u4f4d\u7b49\u65bc&#8217;eval&#8217;\uff0c\u6b64\u6642\u5b50\u67e5\u8a62\u6703\u8fd4\u56denull\u6642\uff0c\u7d50\u679c\u5c0e\u81f4\u4e3b\u67e5\u8a62\u67e5\u4e0d\u5230\u4efb\u4f55\u8cc7\u8a0a\uff0c\u9019\u8207\u9810\u60f3\u7684\u7d50\u679c\u6709\u6240\u843d\u5dee\u3002\u5176\u6b21\uff0c\u5982\u679c<strong>colC=&#8217;eval&#8217;<\/strong>\u6709\u591a\u7b46\u8a18\u9304\uff0c\u9019\u500b\u67e5\u8a62\u5c31\u6703\u51fa\u73fe\u932f\u8aa4\u3002<\/p>\n<p>\u6b64\u6642\u5982\u679c\u5c07=\u6539\u7528in()\uff0c&lt;&gt;\u6539\u7528not in\uff0c\u4f8b\u5982\uff1a<\/p>\n<p><strong>select * from SOME_TABLE where colA\u00a0 not in (select colB from SOME_TABLE where colC=&#8217;eval&#8217;)<\/strong><\/p>\n<p>\u7121\u8ad6\u5b50\u67e5\u8a62\u8fd4\u56denull\u503c\uff0c\u6216\u8005\u8fd4\u56de\u591a\u7b46\u8a18\u9304\uff0c\u7d50\u679c\u90fd\u6b63\u5e38\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>select * from SOME_TABLE where colA &lt;&gt; &#8216;3&#038;# &hellip; <a href=\"https:\/\/wp.chunhsin.idv.tw\/?p=4366\" class=\"more-link\">\u95b1\u8b80\u5168\u6587<span class=\"screen-reader-text\">\u3008\u67e5\u8a62\u689d\u4ef6\u70banull\u6642\u8dd1\u4e0d\u51fa\u6771\u897f\u3009<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[335],"class_list":["post-4366","post","type-post","status-publish","format-standard","hentry","category-mysql","tag-subquery"],"_links":{"self":[{"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=\/wp\/v2\/posts\/4366","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4366"}],"version-history":[{"count":3,"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=\/wp\/v2\/posts\/4366\/revisions"}],"predecessor-version":[{"id":4369,"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=\/wp\/v2\/posts\/4366\/revisions\/4369"}],"wp:attachment":[{"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4366"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4366"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.chunhsin.idv.tw\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4366"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}