{"id":96278,"date":"2024-10-20T08:05:17","date_gmt":"2024-10-20T00:05:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/96278\/"},"modified":"2024-10-20T08:05:18","modified_gmt":"2024-10-20T00:05:18","slug":"oracle%e8%bd%89%e6%8f%9b%e5%87%bd%e6%95%b8%e4%b8%80%e8%a6%bd","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/96278\/","title":{"rendered":"Oracle\u8f49\u63db\u51fd\u6578\u4e00\u89bd"},"content":{"rendered":"<h1 id=\"oracle%e8%bd%89%e6%8f%9b%e5%87%bd%e6%95%b8%e4%b8%80%e8%a6%bd-cqjKbIxyMQ\">Oracle\u8f49\u63db\u51fd\u6578\u4e00\u89bd<\/h1>\n<p>\u5728Oracle\u8cc7\u6599\u5eab\u4e2d\uff0c\u8f49\u63db\u51fd\u6578\u662f\u7528\u4f86\u6539\u8b8a\u6578\u64da\u985e\u578b\u7684\u5de5\u5177\uff0c\u9019\u5c0d\u65bc\u6578\u64da\u8655\u7406\u548c\u67e5\u8a62\u975e\u5e38\u91cd\u8981\u3002\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u5e6b\u52a9\u958b\u767c\u8005\u5728\u4e0d\u540c\u7684\u6578\u64da\u985e\u578b\u4e4b\u9593\u9032\u884c\u8f49\u63db\uff0c\u5f9e\u800c\u63d0\u9ad8\u6578\u64da\u7684\u9748\u6d3b\u6027\u548c\u53ef\u7528\u6027\u3002\u672c\u6587\u5c07\u4ecb\u7d39\u5e7e\u500b\u5e38\u7528\u7684Oracle\u8f49\u63db\u51fd\u6578\uff0c\u4e26\u63d0\u4f9b\u76f8\u61c9\u7684\u7bc4\u4f8b\u3002<\/p>\n<h2 id=\"1-to_char-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">1. TO_CHAR \u51fd\u6578<\/h2>\n<p>TO_CHAR\u51fd\u6578\u4e3b\u8981\u7528\u65bc\u5c07\u6578\u5b57\u6216\u65e5\u671f\u8f49\u63db\u70ba\u5b57\u4e32\u683c\u5f0f\u3002\u9019\u5728\u9700\u8981\u5c07\u6578\u64da\u4ee5\u7279\u5b9a\u683c\u5f0f\u986f\u793a\u6642\u975e\u5e38\u6709\u7528\u3002<\/p>\n<pre><code>SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD') AS formatted_date FROM dual;<\/code><\/pre>\n<p>\u4e0a\u8ff0\u7bc4\u4f8b\u5c07\u7576\u524d\u65e5\u671f\u8f49\u63db\u70ba\u201cYYYY-MM-DD\u201d\u7684\u683c\u5f0f\u3002<\/p>\n<h2 id=\"2-to_number-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">2. TO_NUMBER \u51fd\u6578<\/h2>\n<p>TO_NUMBER\u51fd\u6578\u7528\u65bc\u5c07\u5b57\u4e32\u8f49\u63db\u70ba\u6578\u5b57\u3002\u9019\u5728\u9700\u8981\u9032\u884c\u6578\u5b78\u904b\u7b97\u6642\u975e\u5e38\u91cd\u8981\u3002<\/p>\n<pre><code>SELECT TO_NUMBER('12345.67') AS numeric_value FROM dual;<\/code><\/pre>\n<p>\u9019\u500b\u7bc4\u4f8b\u5c07\u5b57\u4e32&#8217;12345.67&#8217;\u8f49\u63db\u70ba\u6578\u5b57\u683c\u5f0f\u3002<\/p>\n<h2 id=\"3-to_date-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">3. TO_DATE \u51fd\u6578<\/h2>\n<p>TO_DATE\u51fd\u6578\u7528\u65bc\u5c07\u5b57\u4e32\u8f49\u63db\u70ba\u65e5\u671f\u683c\u5f0f\u3002\u9019\u5728\u8655\u7406\u65e5\u671f\u6578\u64da\u6642\u975e\u5e38\u5e38\u898b\u3002<\/p>\n<pre><code>SELECT TO_DATE('2023-10-01', 'YYYY-MM-DD') AS date_value FROM dual;<\/code><\/pre>\n<p>\u9019\u500b\u7bc4\u4f8b\u5c07\u5b57\u4e32&#8217;2023-10-01&#8217;\u8f49\u63db\u70ba\u65e5\u671f\u683c\u5f0f\u3002<\/p>\n<h2 id=\"4-cast-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">4. CAST \u51fd\u6578<\/h2>\n<p>CAST\u51fd\u6578\u662f\u4e00\u500b\u901a\u7528\u7684\u8f49\u63db\u51fd\u6578\uff0c\u53ef\u4ee5\u5c07\u4e00\u500b\u6578\u64da\u985e\u578b\u8f49\u63db\u70ba\u53e6\u4e00\u500b\u6578\u64da\u985e\u578b\u3002\u9019\u500b\u51fd\u6578\u7684\u9748\u6d3b\u6027\u4f7f\u5176\u5728\u591a\u7a2e\u60c5\u6cc1\u4e0b\u90fd\u80fd\u4f7f\u7528\u3002<\/p>\n<pre><code>SELECT CAST('12345' AS NUMBER) AS numeric_value FROM dual;<\/code><\/pre>\n<p>\u9019\u500b\u7bc4\u4f8b\u5c07\u5b57\u4e32&#8217;12345&#8217;\u8f49\u63db\u70ba\u6578\u5b57\u3002<\/p>\n<h2 id=\"5-convert-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">5. CONVERT \u51fd\u6578<\/h2>\n<p>CONVERT\u51fd\u6578\u7528\u65bc\u5728\u4e0d\u540c\u7684\u5b57\u7b26\u96c6\u4e4b\u9593\u9032\u884c\u8f49\u63db\u3002\u9019\u5728\u8655\u7406\u591a\u8a9e\u8a00\u6578\u64da\u6642\u975e\u5e38\u6709\u7528\u3002<\/p>\n<pre><code>SELECT CONVERT('Hello', 'US7ASCII', 'UTF8') AS converted_value FROM dual;<\/code><\/pre>\n<p>\u9019\u500b\u7bc4\u4f8b\u5c07\u5b57\u4e32&#8217;Hello&#8217;\u5f9eUTF8\u5b57\u7b26\u96c6\u8f49\u63db\u70baUS7ASCII\u5b57\u7b26\u96c6\u3002<\/p>\n<h2 id=\"6-nvl-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">6. NVL \u51fd\u6578<\/h2>\n<p>NVL\u51fd\u6578\u7528\u65bc\u5c07NULL\u503c\u8f49\u63db\u70ba\u5176\u4ed6\u6307\u5b9a\u7684\u503c\u3002\u9019\u5728\u8655\u7406\u7f3a\u5931\u6578\u64da\u6642\u975e\u5e38\u6709\u7528\u3002<\/p>\n<pre><code>SELECT NVL(NULL, 'Default Value') AS result FROM dual;<\/code><\/pre>\n<p>\u9019\u500b\u7bc4\u4f8b\u5c07NULL\u503c\u8f49\u63db\u70ba&#8217;Default Value&#8217;\u3002<\/p>\n<h2 id=\"7-coalesce-%e5%87%bd%e6%95%b8-cqjKbIxyMQ\">7. COALESCE \u51fd\u6578<\/h2>\n<p>COALESCE\u51fd\u6578\u8fd4\u56de\u7b2c\u4e00\u500b\u975eNULL\u7684\u503c\u3002\u9019\u5728\u9700\u8981\u5f9e\u591a\u500b\u53ef\u80fd\u7684\u503c\u4e2d\u9078\u64c7\u6642\u975e\u5e38\u6709\u7528\u3002<\/p>\n<pre><code>SELECT COALESCE(NULL, NULL, 'First Non-NULL Value') AS result FROM dual;<\/code><\/pre>\n<p>\u9019\u500b\u7bc4\u4f8b\u5c07\u8fd4\u56de&#8217;First Non-NULL Value&#8217;\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-cqjKbIxyMQ\">\u7e3d\u7d50<\/h2>\n<p>Oracle\u7684\u8f49\u63db\u51fd\u6578\u63d0\u4f9b\u4e86\u5f37\u5927\u7684\u6578\u64da\u8655\u7406\u80fd\u529b\uff0c\u5e6b\u52a9\u958b\u767c\u8005\u5728\u4e0d\u540c\u6578\u64da\u985e\u578b\u4e4b\u9593\u9032\u884c\u9748\u6d3b\u7684\u8f49\u63db\u3002\u7121\u8ad6\u662f\u5c07\u65e5\u671f\u683c\u5f0f\u5316\u3001\u5c07\u5b57\u4e32\u8f49\u63db\u70ba\u6578\u5b57\uff0c\u9084\u662f\u8655\u7406\u591a\u8a9e\u8a00\u5b57\u7b26\u96c6\uff0c\u9019\u4e9b\u51fd\u6578\u90fd\u80fd\u6709\u6548\u5730\u6eff\u8db3\u9700\u6c42\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u61c9\u7528\uff0c\u9078\u64c7\u5408\u9069\u7684\u8f49\u63db\u51fd\u6578\u81f3\u95dc\u91cd\u8981\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u7a69\u5b9a\u7684 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u89e3\u6c7a\u65b9\u6848\uff0cServer.HK \u63d0\u4f9b\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u4e0d\u540c\u7684\u9700\u6c42\u3002\u7121\u8ad6\u662f\u4f01\u696d\u7d1a\u61c9\u7528\u9084\u662f\u500b\u4eba\u9805\u76ee\uff0c\u6211\u5011\u7684 <a href=\"https:\/\/server.hk\">\u4f3a\u670d\u5668<\/a> \u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u53ef\u9760\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22Oracle\u8f49\u63db\u51fd\u6578\u7684\u5168\u9762\u6307\u5357\uff0c\u4e86\u89e3\u5404\u7a2e\u6578\u64da\u985e\u578b\u8f49\u63db\u7684\u7528\u6cd5\u8207\u7bc4\u4f8b\uff0c\u63d0\u5347\u6578\u64da\u8655\u7406\u6548\u7387\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-96278","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/96278","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=96278"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/96278\/revisions"}],"predecessor-version":[{"id":96279,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/96278\/revisions\/96279"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=96278"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=96278"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=96278"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}