{"id":199979,"date":"2025-05-06T08:49:57","date_gmt":"2025-05-06T00:49:57","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199979\/"},"modified":"2025-05-06T08:49:57","modified_gmt":"2025-05-06T00:49:57","slug":"oracle-nvl%e5%87%bd%e6%95%b0%e5%b8%b8%e8%a7%81%e4%bd%bf%e7%94%a8%e9%97%ae%e9%a2%98%e5%92%8c%e8%a7%a3%e5%86%b3%e5%8a%9e%e6%b3%95","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199979\/","title":{"rendered":"Oracle NVL\u51fd\u6570\u5e38\u89c1\u4f7f\u7528\u95ee\u9898\u548c\u89e3\u51b3\u529e\u6cd5"},"content":{"rendered":"

<\/b> <\/p>\n

Oracle NVL\u51fd\u6570\u5e38\u89c1\u4f7f\u7528\u95ee\u9898\u548c\u89e3\u51b3\u529e\u6cd5<\/h1>\n

\u5bf9\u4e8e\u4e00\u4e2a\u6570\u636e\u5e93\u5f00\u53d1\u8005\u6765\u8bf4\uff0c\u7262\u56fa\u624e\u5b9e\u7684\u57fa\u7840\u662f\u5341\u5206\u91cd\u8981\u7684\uff0c\u4e3b\u673a\u5b9d\u8d1d\u5c31\u6765\u5e26\u5927\u5bb6\u4e00\u70b9\u70b9\u7684\u638c\u63e1\u57fa\u7840\u77e5\u8bc6\u70b9\u3002\u4eca\u5929\u672c\u7bc7\u6587\u7ae0\u5e26\u5927\u5bb6\u4e86\u89e3\u300aOracle NVL\u51fd\u6570\u5e38\u89c1\u4f7f\u7528\u95ee\u9898\u548c\u89e3\u51b3\u529e\u6cd5\u300b\uff0c\u4e3b\u8981\u4ecb\u7ecd\u4e86\uff0c\u5e0c\u671b\u5bf9\u5927\u5bb6\u7684\u77e5\u8bc6\u79ef\u7d2f\u6709\u6240\u5e2e\u52a9\uff0c\u5feb\u70b9\u6536\u85cf\u8d77\u6765\u5427\uff0c\u5426\u5219\u9700\u8981\u65f6\u5c31\u627e\u4e0d\u5230\u4e86\uff01<\/p>\n

Oracle NVL\u51fd\u6570\u5e38\u89c1\u95ee\u9898\u53ca\u89e3\u51b3\u65b9\u6848<\/p>\n

Oracle\u6570\u636e\u5e93\u662f\u5e7f\u6cdb\u4f7f\u7528\u7684\u5173\u7cfb\u578b\u6570\u636e\u5e93\u7cfb\u7edf\uff0c\u5728\u6570\u636e\u5904\u7406\u8fc7\u7a0b\u4e2d\u7ecf\u5e38\u9700\u8981\u5904\u7406\u7a7a\u503c\u7684\u60c5\u51b5\u3002\u4e3a\u4e86\u5e94\u5bf9\u7a7a\u503c\u5e26\u6765\u7684\u95ee\u9898\uff0cOracle\u63d0\u4f9b\u4e86NVL\u51fd\u6570\u6765\u5904\u7406\u7a7a\u503c\u3002\u672c\u6587\u5c06\u4ecb\u7ecdNVL\u51fd\u6570\u7684\u5e38\u89c1\u95ee\u9898\u53ca\u89e3\u51b3\u65b9\u6848\uff0c\u5e76\u63d0\u4f9b\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\u3002<\/p>\n

\u95ee\u9898\u4e00\uff1aNVL\u51fd\u6570\u7528\u6cd5\u4e0d\u5f53<\/strong><\/p>\n

NVL\u51fd\u6570\u7684\u57fa\u672c\u8bed\u6cd5\u662f\uff1a<\/p>\n

NVL(expr1, default_value)<\/pre>\n
\u5176\u4e2d\uff0cexpr1\u662f\u9700\u8981\u68c0\u67e5\u662f\u5426\u4e3anull\u7684\u8868\u8fbe\u5f0f\uff0cdefault_value\u662f\u5f53expr1\u4e3anull\u65f6\u8fd4\u56de\u7684\u9ed8\u8ba4\u503c\u3002<\/p>\n
\u5e38\u89c1\u7684\u9519\u8bef\u7528\u6cd5\u5305\u62ec\uff1a<\/p>\n
    \n
  1. \u5fd8\u8bb0\u5904\u7406null\u60c5\u51b5\uff0c\u5bfc\u81f4\u8fd4\u56de\u7ed3\u679c\u4e0d\u7b26\u5408\u671f\u671b\u3002<\/li>\n
  2. \u9ed8\u8ba4\u503c\u4e0d\u7b26\u5408\u6570\u636e\u7c7b\u578b\u8981\u6c42\uff0c\u5bfc\u81f4\u7c7b\u578b\u9519\u8bef\u3002<\/li>\n<\/ol>\n
    \u89e3\u51b3\u65b9\u6848\uff1a<\/strong><\/p>\n
    \u6b63\u786e\u4f7f\u7528NVL\u51fd\u6570\u5e94\u6ce8\u610f\u5904\u7406expr1\u4e3anull\u7684\u60c5\u51b5\uff0c\u786e\u4fdddefault_value\u7684\u6570\u636e\u7c7b\u578b\u4e0eexpr1\u4e00\u81f4\u3002\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\uff1a<\/p>\n
    SELECT NVL(salary, 0) AS emp_salary\nFROM employees;<\/pre>\n
    \u8fd9\u6bb5\u4ee3\u7801\u4eceemployees\u8868\u4e2d\u67e5\u8be2salary\u5b57\u6bb5\uff0c\u5982\u679csalary\u5b57\u6bb5\u4e3anull\uff0c\u5219\u8fd4\u56de0\u4f5c\u4e3a\u9ed8\u8ba4\u503c\u3002\u4fdd\u8bc1\u4e86\u67e5\u8be2\u7ed3\u679c\u4e0d\u4f1a\u51fa\u73b0null\u503c\u3002<\/p>\n
    \u95ee\u9898\u4e8c\uff1aNVL\u51fd\u6570\u5728\u8054\u5408\u67e5\u8be2\u4e2d\u7684\u5e94\u7528<\/strong><\/p>\n
    \u5728\u8fdb\u884c\u8054\u5408\u67e5\u8be2\u65f6\uff0cNVL\u51fd\u6570\u7684\u4f7f\u7528\u53ef\u80fd\u4f1a\u5f15\u53d1\u95ee\u9898\u3002\u7279\u522b\u662f\u5728\u4f7f\u7528NVL\u51fd\u6570\u7684\u5217\u8fdb\u884c\u8fde\u63a5\u65f6\uff0c\u53ef\u80fd\u5bfc\u81f4\u67e5\u8be2\u7ed3\u679c\u4e0d\u7b26\u5408\u9884\u671f\u3002<\/p>\n
    \u89e3\u51b3\u65b9\u6848\uff1a<\/strong><\/p>\n
    \u5728\u8fdb\u884c\u8054\u5408\u67e5\u8be2\u65f6\uff0c\u786e\u4fddNVL\u51fd\u6570\u7684\u4f7f\u7528\u4e0d\u4f1a\u5f71\u54cd\u7ed3\u679c\u96c6\u7684\u8fde\u63a5\u6761\u4ef6\u3002\u4e00\u79cd\u5e38\u89c1\u7684\u89e3\u51b3\u65b9\u6cd5\u662f\u5c06NVL\u51fd\u6570\u7684\u7ed3\u679c\u4f5c\u4e3a\u4e00\u4e2a\u5355\u72ec\u7684\u5217\uff0c\u518d\u8fdb\u884c\u8fde\u63a5\u3002\u793a\u4f8b\u5982\u4e0b\uff1a<\/p>\n
    SELECT e.employee_id, e.employee_name, NVL(s.salary, 0) AS emp_salary\nFROM employees e\nLEFT JOIN salaries s ON e.employee_id = s.employee_id;<\/pre>\n
    \u8fd9\u6bb5\u4ee3\u7801\u5c06employees\u8868\u4e0esalaries\u8868\u8fdb\u884c\u5de6\u8fde\u63a5\uff0c\u5e76\u4f7f\u7528NVL\u51fd\u6570\u5904\u7406salary\u5b57\u6bb5\u7684null\u503c\u3002\u4fdd\u8bc1\u4e86\u67e5\u8be2\u7ed3\u679c\u7684\u5b8c\u6574\u6027\u3002<\/p>\n
    \u95ee\u9898\u4e09\uff1aNVL\u51fd\u6570\u6027\u80fd\u95ee\u9898<\/strong><\/p>\n
    \u7531\u4e8eNVL\u51fd\u6570\u7684\u8fd0\u7b97\u903b\u8f91\uff0c\u53ef\u80fd\u5bfc\u81f4\u4e00\u5b9a\u7684\u6027\u80fd\u5f71\u54cd\uff0c\u7279\u522b\u662f\u5728\u5904\u7406\u5927\u6570\u636e\u91cf\u65f6\u3002<\/p>\n
    \u89e3\u51b3\u65b9\u6848\uff1a<\/strong><\/p>\n
    \u4e3a\u4e86\u63d0\u9ad8\u6027\u80fd\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528COALESCE\u51fd\u6570\u4ee3\u66ffNVL\u51fd\u6570\u3002COALESCE\u51fd\u6570\u63a5\u53d7\u591a\u4e2a\u53c2\u6570\uff0c\u5e76\u8fd4\u56de\u7b2c\u4e00\u4e2a\u975enull\u503c\u3002\u5728\u67d0\u4e9b\u573a\u666f\u4e0b\uff0cCOALESCE\u51fd\u6570\u6bd4NVL\u51fd\u6570\u66f4\u9ad8\u6548\u3002\u793a\u4f8b\u5982\u4e0b\uff1a<\/p>\n
    SELECT COALESCE(salary, 0) AS emp_salary\nFROM employees;<\/pre>\n
    \u901a\u8fc7\u4f7f\u7528COALESCE\u51fd\u6570\uff0c\u907f\u514d\u4e86\u5bf9\u591a\u4e2a\u5217\u8fdb\u884c\u9010\u4e00\u5904\u7406\uff0c\u63d0\u9ad8\u4e86\u67e5\u8be2\u7684\u6548\u7387\u3002<\/p>\n
    \u7efc\u4e0a\u6240\u8ff0\uff0cOracle NVL\u51fd\u6570\u5728\u5904\u7406\u7a7a\u503c\u65f6\u662f\u4e00\u79cd\u91cd\u8981\u7684\u8f85\u52a9\u5de5\u5177\uff0c\u4f46\u5728\u4f7f\u7528\u8fc7\u7a0b\u4e2d\u9700\u8981\u6ce8\u610f\u907f\u514d\u5e38\u89c1\u7684\u95ee\u9898\u5e76\u9009\u62e9\u5408\u9002\u7684\u89e3\u51b3\u65b9\u6848\uff0c\u4ee5\u786e\u4fdd\u67e5\u8be2\u7ed3\u679c\u7684\u51c6\u786e\u6027\u548c\u6027\u80fd\u3002\u5e0c\u671b\u4ee5\u4e0a\u5185\u5bb9\u80fd\u591f\u5e2e\u52a9\u8bfb\u8005\u66f4\u597d\u5730\u7406\u89e3\u548c\u5e94\u7528NVL\u51fd\u6570\u3002<\/p>\n
    \u4ee5\u4e0a\u5c31\u662f\u300aOracle NVL\u51fd\u6570\u5e38\u89c1\u4f7f\u7528\u95ee\u9898\u548c\u89e3\u51b3\u529e\u6cd5\u300b\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u5173\u4e8eOracle,\u89e3\u51b3\u65b9\u6848,NVL\u7684\u8d44\u6599\u8bf7\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff01<\/p>\n
    \n
    \n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"
    Oracle NVL\u51fd\u6570\u5e38\u89c1\u4f7f\u7528...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-199979","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199979","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=199979"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199979\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199979"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199979"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199979"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}