{"id":3697,"date":"2025-05-10T18:01:29","date_gmt":"2025-05-10T10:01:29","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3697"},"modified":"2025-05-10T18:01:29","modified_gmt":"2025-05-10T10:01:29","slug":"%e4%b8%ba%e4%bb%80%e4%b9%88-mysql-%e4%b8%8d%e5%bb%ba%e8%ae%ae%e4%bd%bf%e7%94%a8-null-%e4%bd%9c%e4%b8%ba%e5%88%97%e7%9a%84%e9%bb%98%e8%ae%a4%e5%80%bc%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/05\/10\/%e4%b8%ba%e4%bb%80%e4%b9%88-mysql-%e4%b8%8d%e5%bb%ba%e8%ae%ae%e4%bd%bf%e7%94%a8-null-%e4%bd%9c%e4%b8%ba%e5%88%97%e7%9a%84%e9%bb%98%e8%ae%a4%e5%80%bc%ef%bc%9f\/","title":{"rendered":"\u4e3a\u4ec0\u4e48 MySQL \u4e0d\u5efa\u8bae\u4f7f\u7528 NULL \u4f5c\u4e3a\u5217\u7684\u9ed8\u8ba4\u503c\uff1f"},"content":{"rendered":"\n

\u4e00\u3001\u901a\u5e38\u60c5\u51b5\u4e0b\uff0c\u9762\u8bd5\u5b98\u63d0\u51fa\u8fd9\u4e2a\u95ee\u9898\u80cc\u540e\u7684\u76ee\u7684\u6709\u5982\u4e0b\u51e0\u4e2a<\/h3>\n\n\n\n
    \n
  1. \u8003\u5bdf\u6570\u636e\u5e93\u8bbe\u8ba1\u89c4\u8303<\/strong>\uff1a\u9762\u8bd5\u5b98\u5e0c\u671b\u6d4b\u8bd5\u5e94\u8058\u8005\u5bf9\u6570\u636e\u5e93\u8bbe\u8ba1\u7684\u7406\u89e3\uff0c\u5c24\u5176\u662f\u9ed8\u8ba4\u503c\u7684\u4f7f\u7528\u4ee5\u53ca\u6f5c\u5728\u7684\u6027\u80fd\u95ee\u9898\u3002<\/li>\n\n\n\n
  2. \u4e86\u89e3\u6570\u636e\u4e00\u81f4\u6027<\/strong>\uff1a\u901a\u8fc7\u8fd9\u4e2a\u95ee\u9898\uff0c\u9762\u8bd5\u5b98\u60f3\u77e5\u9053\u5e94\u8058\u8005\u662f\u5426\u610f\u8bc6\u5230\u6570\u636e\u5e93\u4e2d\u4f7f\u7528 NULL \u503c\u53ef\u80fd\u5e26\u6765\u7684\u98ce\u9669\uff0c\u5982\u6570\u636e\u5b8c\u6574\u6027\u3001\u67e5\u8be2\u4f18\u5316\u548c\u5e94\u7528\u5c42\u903b\u8f91\u7b49\u65b9\u9762\u7684\u5f71\u54cd\u3002<\/li>\n\n\n\n
  3. \u63a2\u7d22\u4f18\u5316\u610f\u8bc6<\/strong>\uff1a\u901a\u8fc7\u8fd9\u79cd\u8bbe\u8ba1\u9009\u62e9\u7684\u8ba8\u8bba\uff0c\u9762\u8bd5\u5b98\u53ef\u80fd\u5728\u8bc4\u4f30\u5e94\u8058\u8005\u662f\u5426\u80fd\u505a\u51fa\u9ad8\u6548\u4e14\u7b26\u5408\u6700\u4f73\u5b9e\u8df5\u7684\u6570\u636e\u5e93\u8bbe\u8ba1\u51b3\u7b56\u3002<\/li>\n<\/ol>\n\n\n\n

    \u4e8c\u3001\u7b80\u5316\u7248\u7b54\u6848<\/h3>\n\n\n\n

    MySQL \u4e0d\u5efa\u8bae\u4f7f\u7528 NULL<\/strong> \u4f5c\u4e3a\u5217\u7684\u9ed8\u8ba4\u503c\uff0c\u4e3b\u8981\u539f\u56e0\u6709\u4ee5\u4e0b\u51e0\u70b9\uff1a<\/p>\n\n\n\n

      \n
    1. NULL\u4f1a\u5bfc\u81f4\u4e0d\u5fc5\u8981\u7684\u590d\u6742\u6027<\/strong>\uff1a\u4f7f\u7528 NULL \u4f5c\u4e3a\u9ed8\u8ba4\u503c\u53ef\u80fd\u4f7f\u5f97\u67e5\u8be2\u3001\u63d2\u5165\u548c\u66f4\u65b0\u64cd\u4f5c\u66f4\u52a0\u590d\u6742\uff0c\u9700\u8981\u989d\u5916\u5904\u7406 NULL \u503c\u7684\u903b\u8f91\u3002<\/li>\n\n\n\n
    2. \u6027\u80fd\u95ee\u9898<\/strong>\uff1aNULL \u503c\u53ef\u80fd\u4f1a\u5f71\u54cd\u7d22\u5f15\u7684\u6027\u80fd\uff0c\u5c24\u5176\u662f\u5728\u67e5\u8be2\u4e2d\u6d89\u53ca\u5230 NULL \u503c\u6bd4\u8f83\u65f6\uff0c\u6548\u7387\u8f83\u4f4e\u3002<\/li>\n\n\n\n
    3. \u907f\u514d\u6570\u636e\u4e0d\u4e00\u81f4<\/strong>\uff1aNULL \u4f5c\u4e3a\u9ed8\u8ba4\u503c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u6570\u636e\u5b8c\u6574\u6027\u95ee\u9898\uff0c\u4f8b\u5982\u67d0\u4e9b\u60c5\u51b5\u4e0b\u4e0d\u5c0f\u5fc3\u63d2\u5165\u4e86 NULL \u503c\uff0c\u53ef\u80fd\u4f7f\u5f97\u5e94\u7528\u7a0b\u5e8f\u51fa\u73b0\u610f\u6599\u4e4b\u5916\u7684\u9519\u8bef\u3002<\/li>\n<\/ol>\n\n\n\n

      \u4e09\u3001\u89e3\u51b3\u65b9\u6848\u4e0e\u6700\u4f73\u5b9e\u8df5<\/h3>\n\n\n\n
        \n
      1. \u4f7f\u7528\u9002\u5f53\u7684\u9ed8\u8ba4\u503c<\/strong><\/li>\n<\/ol>\n\n\n\n
          \n
        • \u5982\u679c\u5217\u5141\u8bb8\u7a7a\u503c\uff0c\u4f46\u53c8\u5e0c\u671b\u907f\u514d\u9ed8\u8ba4\u503c\u4e3a NULL\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528\u5176\u4ed6\u66f4\u5408\u9002\u7684\u9ed8\u8ba4\u503c\uff0c\u5982 \u7a7a\u5b57\u7b26\u4e32<\/strong>\uff08\"\"<\/code>\uff09\u6216 0<\/strong>\uff08\u5bf9\u4e8e\u6570\u503c\u7c7b\u578b\uff09\uff0c\u8fd9\u6837\u53ef\u4ee5\u907f\u514d\u7a7a\u503c\u5e26\u6765\u7684\u590d\u6742\u6027\u3002<\/li>\n<\/ul>\n\n\n\n
            \n
          1. \u6dfb\u52a0\u7ea6\u675f<\/strong><\/li>\n<\/ol>\n\n\n\n
              \n
            • \u5bf9\u4e8e\u4e0d\u80fd\u4e3a NULL \u7684\u5217\uff0c\u5e94\u6dfb\u52a0 NOT NULL<\/strong> \u7ea6\u675f\uff0c\u786e\u4fdd\u5728\u63d2\u5165\u6570\u636e\u65f6\u6bcf\u884c\u6570\u636e\u90fd\u6709\u660e\u786e\u7684\u503c\u3002<\/li>\n<\/ul>\n\n\n\n
                \n
              1. \u5408\u7406\u4f7f\u7528 NULL \u503c<\/strong><\/li>\n<\/ol>\n\n\n\n
                  \n
                • \u5982\u679c\u786e\u5b9e\u9700\u8981\u8868\u793a\u7a7a\u6216\u7f3a\u5931\u6570\u636e\uff0c\u5e94\u8be5\u5728\u8bbe\u8ba1\u65f6\u5408\u7406\u5730\u4f7f\u7528 NULL\uff0c\u5e76\u5728\u5e94\u7528\u7a0b\u5e8f\u5c42\u9762\u8fdb\u884c\u9002\u5f53\u7684\u5904\u7406\u3002\u786e\u4fdd NULL \u503c\u7684\u4f7f\u7528\u6709\u660e\u786e\u7684\u4e1a\u52a1\u9700\u6c42\u3002<\/li>\n<\/ul>\n\n\n\n

                  \u56db\u3001\u9762\u8bd5\u56de\u7b54\u8981\u70b9\u603b\u7ed3<\/h3>\n\n\n\n
                    \n
                  1. \u4e0d\u63a8\u8350\u4f7f\u7528 NULL \u4f5c\u4e3a\u5217\u7684\u9ed8\u8ba4\u503c<\/strong>\uff0c\u4e3b\u8981\u56e0\u4e3a\u5b83\u53ef\u80fd\u589e\u52a0\u67e5\u8be2\u7684\u590d\u6742\u5ea6\u3001\u5f71\u54cd\u6027\u80fd\uff0c\u5e76\u4e14\u53ef\u80fd\u5bfc\u81f4\u6570\u636e\u7684\u4e0d\u4e00\u81f4\u6027\u3002<\/li>\n\n\n\n
                  2. \u6027\u80fd\u95ee\u9898<\/strong>\uff1a\u4f7f\u7528 NULL \u4f5c\u4e3a\u9ed8\u8ba4\u503c\u53ef\u80fd\u4f1a\u4f7f\u5f97\u7d22\u5f15\u6548\u7387\u8f83\u4f4e\uff0c\u67e5\u8be2\u6d89\u53ca NULL \u7684\u6761\u4ef6\uff08\u4f8b\u5982 IS NULL<\/code>\uff09\u6027\u80fd\u5dee\u3002<\/li>\n\n\n\n
                  3. \u6570\u636e\u5b8c\u6574\u6027<\/strong>\uff1aNULL \u503c\u53ef\u80fd\u8868\u793a\u7f3a\u5931\u6216\u672a\u77e5\u7684\u72b6\u6001\uff0c\u4f46\u8fc7\u5ea6\u4f7f\u7528\u53ef\u80fd\u4f1a\u5bfc\u81f4\u4e0d\u4e00\u81f4\u7684\u6570\u636e\u548c\u6f5c\u5728\u7684\u4e1a\u52a1\u903b\u8f91\u9519\u8bef\u3002<\/li>\n\n\n\n
                  4. \u5efa\u8bae\u65b9\u6848<\/strong>\uff1a<\/li>\n<\/ol>\n\n\n\n
                      \n
                    • \u4f7f\u7528 \u9002\u5f53\u7684\u9ed8\u8ba4\u503c<\/strong>\uff0c\u5982\u7a7a\u5b57\u7b26\u4e32\u6216\u96f6\uff0c\u6765\u907f\u514d NULL \u503c\u5e26\u6765\u7684\u590d\u6742\u6027\u3002<\/li>\n\n\n\n
                    • \u6dfb\u52a0 NOT NULL<\/strong> \u7ea6\u675f\uff0c\u786e\u4fdd\u6570\u636e\u7684\u5b8c\u6574\u6027\u3002<\/li>\n\n\n\n
                    • \u5728\u5fc5\u8981\u65f6\uff0c\u5408\u7406\u4f7f\u7528 NULL \u503c<\/strong>\uff0c\u786e\u4fdd\u5176\u5728\u4e1a\u52a1\u4e0a\u6709\u660e\u786e\u7684\u8bed\u4e49\u3002<\/li>\n<\/ul>\n\n\n\n

                      \u901a\u8fc7\u8fd9\u4e2a\u95ee\u9898\uff0c\u9762\u8bd5\u5b98\u80fd\u591f\u8bc4\u4f30\u4f60\u662f\u5426\u5177\u5907\u826f\u597d\u7684\u6570\u636e\u5e93\u8bbe\u8ba1\u601d\u7ef4\uff0c\u5e76\u4e14\u77e5\u9053\u5982\u4f55\u5728\u5b9e\u9645\u5de5\u4f5c\u4e2d\u505a\u51fa\u7b26\u5408\u6700\u4f73\u5b9e\u8df5\u7684\u8bbe\u8ba1\u51b3\u7b56\u3002<\/p>\n\n\n\n

                      \n\n\n\n

                      \u6700\u540e\u8ba9\u7136\u63d0\u9192\u4e00\u70b9\u7684\u662f\uff1a\u5f53\u9762\u8bd5\u5b98\u95ee\u5230\u8fd9\u4e2a\u95ee\u9898\u662f\uff0c\u7b54\u6848\u4e0e\u00a0NULL<\/strong>\u00a0\u548c\u00a0\u7a7a\u5b57\u7b26\u4e32 (“”)<\/strong>\u00a0\u4e4b\u95f4\u7684\u533a\u522b\u662f\u5bc6\u5207\u76f8\u5173\u7684\uff0c\u4e0b\u7bc7\u6587\u7ae0\u8bb2\u8be6\u7ec6\u4ecb\u7ecd\u4e24\u8005\u7684\u533a\u522b\uff0c\u4ee5\u53ca\u53e6\u5916\u4e00\u79cd\u56de\u7b54\u7684\u65b9\u5f0f\u3002<\/p>\n\n\n\n

                      \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"

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