{"id":96,"date":"2017-08-01T16:03:41","date_gmt":"2017-08-01T08:03:41","guid":{"rendered":"https:\/\/wp.dj47.top\/?p=96"},"modified":"2021-10-20T16:19:18","modified_gmt":"2021-10-20T08:19:18","slug":"mysql%e6%9f%a5%e8%af%a2%e5%ad%97%e6%ae%b5%e4%b8%banull","status":"publish","type":"post","link":"https:\/\/www.djlog.cn\/?p=96","title":{"rendered":"Mysql\u67e5\u8be2\u5b57\u6bb5\u4e3aNULL"},"content":{"rendered":"<p>\u5728<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/sql\" target=\"_blank\" rel=\"noopener\">SQL<\/a>\u4e2d\uff0c<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/null\" target=\"_blank\" rel=\"noopener\">NULL<\/a>\u503c\u5728\u4e8e\u4efb\u4f55<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E5%85%B6%E4%BB%96\" target=\"_blank\" rel=\"noopener\">\u5176\u4ed6<\/a>\u503c\u751a\u81f3NULL\u503c\u6bd4\u8f83\u65f6\u603b\u662f\u5047\u7684\uff08<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/false\" target=\"_blank\" rel=\"noopener\">FALSE<\/a>\uff09\u3002\u5305\u542bNULL\u7684\u4e00\u4e2a\u8868\u8fbe\u5f0f\u603b\u662f\u4ea7\u751f\u4e00\u4e2aNULL\u503c\uff0c\u9664\u975e\u5728\u5305\u542b\u5728\u8868\u8fbe\u5f0f\u4e2d\u7684<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E8%BF%90%E7%AE%97%E7%AC%A6\" target=\"_blank\" rel=\"noopener\">\u8fd0\u7b97\u7b26<\/a>\u548c<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E5%87%BD%E6%95%B0\" target=\"_blank\" rel=\"noopener\">\u51fd\u6570<\/a>\u7684<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E6%96%87%E6%A1%A3\" target=\"_blank\" rel=\"noopener\">\u6587\u6863<\/a>\u4e2d\u6307\u51fa\u3002<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/mysql\" target=\"_blank\" rel=\"noopener\">mysql<\/a>\u4e2d \u65b0\u5efa\u5b57\u6bb5\u9ed8\u8ba4\u503c\u4e3anull,\u90a3\u4e48\u8981<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E6%9F%A5%E8%AF%A2\" target=\"_blank\" rel=\"noopener\">\u67e5\u8be2<\/a>\u6b64<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E6%95%B0%E6%8D%AE\" target=\"_blank\" rel=\"noopener\">\u6570\u636e<\/a>\u7684\u5b57\u6bb5\u65f6\u5e94\u8be5\u600e\u4e48\u64cd\u4f5c\u5462\uff1f<\/p>\n<p>\u5728mysql\u4e2d\uff0c\u67e5\u8be2\u67d0\u5b57\u6bb5\u4e3a\u7a7a\u65f6\uff0c<a class=\"inlink\" href=\"http:\/\/www.169it.com\/tag\/%E4%B8%8D%E5%8F%AF%E7%94%A8\" target=\"_blank\" rel=\"noopener\">\u4e0d\u53ef\u7528<\/a> = null\uff0c\u800c\u662f is null\uff0c\u4e0d\u4e3a\u7a7a\u5219\u662f is not null\u3002<\/p>\n<p><code>select\u00a0*\u00a0from\u00a0[table\u00a0name]\u00a0where\u00a0[column\u00a0name]\u00a0is\u00a0null;<br \/>\nselect\u00a0*\u00a0from\u00a0[table\u00a0name]\u00a0where\u00a0[column\u00a0name]\u00a0is\u00a0not\u00a0null;<\/code><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728SQL\u4e2d\uff0cNULL\u503c\u5728\u4e8e\u4efb\u4f55\u5176\u4ed6\u503c\u751a\u81f3NULL\u503c\u6bd4\u8f83\u65f6\u603b\u662f\u5047\u7684\uff08FALSE\uff09\u3002\u5305\u542bNULL\u7684\u4e00\u4e2a\u8868\u8fbe\u5f0f\u603b\u662f\u4ea7 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[5],"tags":[],"class_list":["post-96","post","type-post","status-publish","format-standard","hentry","category-mysql"],"_links":{"self":[{"href":"https:\/\/www.djlog.cn\/index.php?rest_route=\/wp\/v2\/posts\/96","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.djlog.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.djlog.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.djlog.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.djlog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=96"}],"version-history":[{"count":0,"href":"https:\/\/www.djlog.cn\/index.php?rest_route=\/wp\/v2\/posts\/96\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.djlog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=96"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.djlog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=96"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.djlog.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=96"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}