{"id":94908,"date":"2024-10-19T20:54:18","date_gmt":"2024-10-19T12:54:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/94908\/"},"modified":"2024-10-19T20:54:18","modified_gmt":"2024-10-19T12:54:18","slug":"oracle%e6%9f%a5%e8%a9%a2%e5%84%aa%e5%8c%96%e4%b9%8bis-null%e5%92%8cis-not-null%e5%84%aa%e5%8c%96","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/94908\/","title":{"rendered":"Oracle\u67e5\u8a62\u512a\u5316\u4e4bis null\u548cis not null\u512a\u5316"},"content":{"rendered":"<h1 id=\"oracle%e6%9f%a5%e8%a9%a2%e5%84%aa%e5%8c%96%e4%b9%8bis-null%e5%92%8cis-not-null%e5%84%aa%e5%8c%96-KjCWCcbRIr\">Oracle\u67e5\u8a62\u512a\u5316\u4e4bIS NULL\u548cIS NOT NULL\u512a\u5316<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u67e5\u8a62\u6027\u80fd\u7684\u512a\u5316\u662f\u63d0\u5347\u61c9\u7528\u7a0b\u5e8f\u6548\u7387\u7684\u95dc\u9375\u56e0\u7d20\u4e4b\u4e00\u3002Oracle\u6578\u64da\u5eab\u4f5c\u70ba\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u7cfb\u7d71\uff0c\u5176\u67e5\u8a62\u512a\u5316\u6280\u8853\u5c24\u70ba\u91cd\u8981\u3002\u5728\u9019\u7bc7\u6587\u7ae0\u4e2d\uff0c\u6211\u5011\u5c07\u63a2\u8a0e\u5982\u4f55\u512a\u5316Oracle\u67e5\u8a62\u4e2d\u7684IS NULL\u548cIS NOT NULL\u689d\u4ef6\uff0c\u4e26\u63d0\u4f9b\u4e00\u4e9b\u5be6\u7528\u7684\u793a\u4f8b\u548c\u5efa\u8b70\u3002<\/p>\n<h2 id=\"is-null%e5%92%8cis-not-null%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-KjCWCcbRIr\">IS NULL\u548cIS NOT NULL\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p>\u5728SQL\u67e5\u8a62\u4e2d\uff0cIS NULL\u548cIS NOT NULL\u7528\u65bc\u6aa2\u67e5\u67d0\u500b\u5b57\u6bb5\u662f\u5426\u70ba\u7a7a\u503c\u3002\u9019\u5728\u8655\u7406\u6578\u64da\u6642\u975e\u5e38\u5e38\u898b\uff0c\u5c24\u5176\u662f\u5728\u6578\u64da\u5b8c\u6574\u6027\u548c\u6578\u64da\u6e05\u7406\u7684\u904e\u7a0b\u4e2d\u3002<\/p>\n<ul>\n<li><strong>IS NULL<\/strong>: \u7528\u65bc\u67e5\u8a62\u90a3\u4e9b\u5b57\u6bb5\u503c\u70baNULL\u7684\u8a18\u9304\u3002<\/li>\n<li><strong>IS NOT NULL<\/strong>: \u7528\u65bc\u67e5\u8a62\u90a3\u4e9b\u5b57\u6bb5\u503c\u4e0d\u70baNULL\u7684\u8a18\u9304\u3002<\/li>\n<\/ul>\n<h2 id=\"%e6%9f%a5%e8%a9%a2%e6%80%a7%e8%83%bd%e7%9a%84%e6%8c%91%e6%88%b0-KjCWCcbRIr\">\u67e5\u8a62\u6027\u80fd\u7684\u6311\u6230<\/h2>\n<p>\u5728\u5927\u578b\u6578\u64da\u96c6\u4e0a\u57f7\u884c\u5305\u542bIS NULL\u6216IS NOT NULL\u7684\u67e5\u8a62\u6642\uff0c\u53ef\u80fd\u6703\u9047\u5230\u6027\u80fd\u74f6\u9838\u3002\u9019\u662f\u56e0\u70baNULL\u503c\u7684\u5b58\u5728\u6703\u5f71\u97ff\u7d22\u5f15\u7684\u4f7f\u7528\uff0c\u5f9e\u800c\u5c0e\u81f4\u5168\u8868\u6383\u63cf\uff0c\u589e\u52a0\u67e5\u8a62\u7684\u57f7\u884c\u6642\u9593\u3002<\/p>\n<h2 id=\"%e5%84%aa%e5%8c%96is-null%e5%92%8cis-not-null%e6%9f%a5%e8%a9%a2%e7%9a%84%e7%ad%96%e7%95%a5-KjCWCcbRIr\">\u512a\u5316IS NULL\u548cIS NOT NULL\u67e5\u8a62\u7684\u7b56\u7565<\/h2>\n<h3 id=\"1-%e4%bd%bf%e7%94%a8%e7%b4%a2%e5%bc%95-KjCWCcbRIr\">1. \u4f7f\u7528\u7d22\u5f15<\/h3>\n<p>\u70ba\u4e86\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\uff0c\u5efa\u8b70\u5728\u7d93\u5e38\u4f7f\u7528IS NULL\u6216IS NOT NULL\u689d\u4ef6\u7684\u5b57\u6bb5\u4e0a\u5275\u5efa\u7d22\u5f15\u3002\u9019\u6a23\u53ef\u4ee5\u52a0\u901f\u67e5\u8a62\u904e\u7a0b\uff0c\u6e1b\u5c11\u5168\u8868\u6383\u63cf\u7684\u53ef\u80fd\u6027\u3002<\/p>\n<pre><code>CREATE INDEX idx_column_name ON table_name(column_name) WHERE column_name IS NULL;<\/code><\/pre>\n<p>\u4e0a\u8ff0\u4ee3\u78bc\u793a\u4f8b\u5c55\u793a\u4e86\u5982\u4f55\u70ba\u7279\u5b9a\u5b57\u6bb5\u5275\u5efa\u4e00\u500b\u91dd\u5c0dNULL\u503c\u7684\u7d22\u5f15\u3002\u9019\u6a23\u7684\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002<\/p>\n<h3 id=\"2-%e9%81%bf%e5%85%8d%e4%b8%8d%e5%bf%85%e8%a6%81%e7%9a%84null%e6%aa%a2%e6%9f%a5-KjCWCcbRIr\">2. \u907f\u514d\u4e0d\u5fc5\u8981\u7684NULL\u6aa2\u67e5<\/h3>\n<p>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u67e5\u8a62\u4e2d\u53ef\u80fd\u5305\u542b\u4e0d\u5fc5\u8981\u7684NULL\u6aa2\u67e5\u3002\u9019\u6703\u5c0e\u81f4\u6027\u80fd\u4e0b\u964d\u3002\u5efa\u8b70\u5728\u8a2d\u8a08\u6578\u64da\u6a21\u578b\u6642\uff0c\u76e1\u91cf\u907f\u514d\u4f7f\u7528NULL\u503c\uff0c\u6216\u8005\u5728\u61c9\u7528\u5c64\u9032\u884cNULL\u503c\u7684\u8655\u7406\u3002<\/p>\n<h3 id=\"3-%e4%bd%bf%e7%94%a8coalesce%e5%87%bd%e6%95%b8-KjCWCcbRIr\">3. \u4f7f\u7528COALESCE\u51fd\u6578<\/h3>\n<p>COALESCE\u51fd\u6578\u53ef\u4ee5\u7528\u4f86\u66ff\u4ee3NULL\u503c\uff0c\u5f9e\u800c\u907f\u514d\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528IS NULL\u3002\u4f8b\u5982\uff0c\u53ef\u4ee5\u5c07NULL\u503c\u66ff\u63db\u70ba\u4e00\u500b\u9810\u8a2d\u503c\uff0c\u9019\u6a23\u53ef\u4ee5\u7c21\u5316\u67e5\u8a62\u908f\u8f2f\u3002<\/p>\n<pre><code>SELECT COALESCE(column_name, 'default_value') FROM table_name;<\/code><\/pre>\n<h3 id=\"4-%e5%88%86%e6%9e%90%e5%9f%b7%e8%a1%8c%e8%a8%88%e5%8a%83-KjCWCcbRIr\">4. \u5206\u6790\u57f7\u884c\u8a08\u5283<\/h3>\n<p>\u4f7f\u7528Oracle\u7684EXPLAIN PLAN\u529f\u80fd\u4f86\u5206\u6790\u67e5\u8a62\u7684\u57f7\u884c\u8a08\u5283\uff0c\u53ef\u4ee5\u5e6b\u52a9\u8b58\u5225\u6027\u80fd\u74f6\u9838\u3002\u901a\u904e\u67e5\u770b\u57f7\u884c\u8a08\u5283\uff0c\u53ef\u4ee5\u4e86\u89e3\u67e5\u8a62\u662f\u5426\u4f7f\u7528\u4e86\u7d22\u5f15\uff0c\u4e26\u6839\u64da\u9700\u8981\u9032\u884c\u8abf\u6574\u3002<\/p>\n<pre><code>EXPLAIN PLAN FOR SELECT * FROM table_name WHERE column_name IS NULL;<\/code><\/pre>\n<h2 id=\"%e7%b5%90%e8%ab%96-KjCWCcbRIr\">\u7d50\u8ad6<\/h2>\n<p>\u5728Oracle\u6578\u64da\u5eab\u4e2d\uff0cIS NULL\u548cIS NOT NULL\u7684\u67e5\u8a62\u512a\u5316\u662f\u63d0\u5347\u67e5\u8a62\u6027\u80fd\u7684\u91cd\u8981\u65b9\u9762\u3002\u901a\u904e\u5408\u7406\u4f7f\u7528\u7d22\u5f15\u3001\u907f\u514d\u4e0d\u5fc5\u8981\u7684NULL\u6aa2\u67e5\u3001\u5229\u7528COALESCE\u51fd\u6578\u4ee5\u53ca\u5206\u6790\u57f7\u884c\u8a08\u5283\uff0c\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6548\u7387\u3002\u9019\u4e9b\u7b56\u7565\u4e0d\u50c5\u80fd\u5920\u6539\u5584\u67e5\u8a62\u6027\u80fd\uff0c\u9084\u80fd\u63d0\u5347\u6574\u9ad4\u7cfb\u7d71\u7684\u97ff\u61c9\u901f\u5ea6\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a>\u4f86\u652f\u6301\u60a8\u7684\u61c9\u7528\u7a0b\u5e8f\uff0c\u78ba\u4fdd\u6700\u4f73\u7684\u6027\u80fd\u548c\u7a69\u5b9a\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22Oracle\u67e5\u8a62\u512a\u5316\u6280\u5de7\uff0c\u4e86\u89e3\u5982\u4f55\u6709\u6548\u4f7f\u7528IS NULL\u548cIS NOT NULL\u4f86\u63d0\u5347\u67e5\u8a62\u6027\u80fd\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-94908","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/94908","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=94908"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/94908\/revisions"}],"predecessor-version":[{"id":94915,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/94908\/revisions\/94915"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=94908"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=94908"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=94908"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}