{"id":963,"date":"2025-01-15T00:37:00","date_gmt":"2025-01-14T16:37:00","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=963"},"modified":"2025-01-15T00:37:00","modified_gmt":"2025-01-14T16:37:00","slug":"%e4%b8%ba%e4%bb%80%e4%b9%88%e5%9c%a8-sql-%e4%b8%ad%e6%b7%b7%e5%90%88%e9%9a%90%e5%bc%8f%e5%92%8c%e6%98%be%e5%bc%8f%e8%bf%9e%e6%8e%a5%e4%bc%9a%e5%af%bc%e8%87%b4%e8%af%ad%e6%b3%95%e9%94%99%e8%af%af","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/01\/15\/%e4%b8%ba%e4%bb%80%e4%b9%88%e5%9c%a8-sql-%e4%b8%ad%e6%b7%b7%e5%90%88%e9%9a%90%e5%bc%8f%e5%92%8c%e6%98%be%e5%bc%8f%e8%bf%9e%e6%8e%a5%e4%bc%9a%e5%af%bc%e8%87%b4%e8%af%ad%e6%b3%95%e9%94%99%e8%af%af\/","title":{"rendered":"\u4e3a\u4ec0\u4e48\u5728 SQL \u4e2d\u6df7\u5408\u9690\u5f0f\u548c\u663e\u5f0f\u8fde\u63a5\u4f1a\u5bfc\u81f4\u8bed\u6cd5\u9519\u8bef\uff1f\u89e3\u51b3\u65b9\u6848\u4e0e\u6700\u4f73\u5b9e\u8df5"},"content":{"rendered":"\n
\n

\u5728 SQL \u4e2d\uff0c\u9690\u5f0f\u8fde\u63a5\uff08Implicit Join\uff09<\/strong>\u548c\u663e\u5f0f\u8fde\u63a5\uff08Explicit Join\uff09<\/strong>\u662f\u4e24\u79cd\u7528\u4e8e\u5c06\u591a\u4e2a\u8868\u8fde\u63a5\u5728\u4e00\u8d77\u7684\u65b9\u5f0f\u3002\u5b83\u4eec\u5728\u8bed\u6cd5\u7ed3\u6784\u548c\u5904\u7406\u903b\u8f91\u4e0a\u6709\u6240\u4e0d\u540c\u3002\u5f53\u6211\u4eec\u5728\u540c\u4e00\u6761 SQL \u67e5\u8be2\u4e2d\u540c\u65f6\u4f7f\u7528\u9690\u5f0f\u8fde\u63a5\u548c\u663e\u5f0f\u8fde\u63a5\u65f6\uff0c\u901a\u5e38\u4f1a\u5bfc\u81f4\u8bed\u6cd5\u9519\u8bef<\/strong>\u3002\u4e0b\u9762\u5c06\u8be6\u7ec6\u89e3\u91ca\u4e3a\u4ec0\u4e48\u4f1a\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\uff0c\u5e76\u5206\u6790\u4e24\u8005\u7684\u533a\u522b\u3002<\/p>\n<\/blockquote>\n\n\n\n

1. \u9690\u5f0f\u8fde\u63a5\u548c\u663e\u5f0f\u8fde\u63a5\u7684\u5b9a\u4e49<\/strong><\/h3>\n\n\n\n
    \n
  • \u9690\u5f0f\u8fde\u63a5\uff08Implicit Join\uff09<\/strong>\uff1a
    \u9690\u5f0f\u8fde\u63a5\u662f\u901a\u8fc7\u5728 WHERE<\/code> \u5b50\u53e5\u4e2d\u76f4\u63a5\u6307\u5b9a\u8fde\u63a5\u6761\u4ef6\u6765\u5b9e\u73b0\u7684\u3002\u5728\u65e9\u671f\u7684 SQL \u4e2d\uff0c\u9690\u5f0f\u8fde\u63a5\u662f\u6700\u5e38\u7528\u7684\u8fde\u63a5\u65b9\u5f0f\u3002\u8fde\u63a5\u6761\u4ef6\u901a\u5e38\u5728 WHERE<\/code> \u5b50\u53e5\u4e2d\u5b9a\u4e49\uff0c\u800c\u4e0d\u662f\u4f7f\u7528\u663e\u5f0f\u7684 JOIN<\/code> \u8bed\u6cd5\u3002 \u793a\u4f8b\uff08\u9690\u5f0f\u8fde\u63a5\uff09\uff1a<\/strong><\/li>\n<\/ul>\n\n\n\n
      SELECT employees.name, departments.department_name\n  FROM employees, departments\n  WHERE employees.department_id = departments.department_id;<\/code><\/pre>\n\n\n\n
    \u5728\u8fd9\u4e2a\u67e5\u8be2\u4e2d\uff0cemployees<\/code> \u548c departments<\/code> \u8868\u901a\u8fc7 WHERE<\/code> \u5b50\u53e5\u4e2d\u7684\u8fde\u63a5\u6761\u4ef6\u8fdb\u884c\u8fde\u63a5\u3002<\/p>\n\n\n\n
      \n
    • \u663e\u5f0f\u8fde\u63a5\uff08Explicit Join\uff09<\/strong>\uff1a
      \u663e\u5f0f\u8fde\u63a5\u4f7f\u7528 SQL \u6807\u51c6\u7684 JOIN<\/code> \u8bed\u6cd5\uff0c\u5b83\u660e\u786e\u6307\u5b9a\u4e86\u8fde\u63a5\u7c7b\u578b\uff08\u5982 INNER JOIN<\/code>\u3001LEFT JOIN<\/code>\u3001RIGHT JOIN<\/code> \u7b49\uff09\u548c\u8fde\u63a5\u6761\u4ef6\u3002\u663e\u5f0f\u8fde\u63a5\u63d0\u4f9b\u4e86\u66f4\u6e05\u6670\u7684\u8bed\u6cd5\uff0c\u5e76\u4e14\u5bf9\u4e8e\u590d\u6742\u67e5\u8be2\u66f4\u5177\u53ef\u8bfb\u6027\u548c\u53ef\u7ef4\u62a4\u6027\u3002 \u793a\u4f8b\uff08\u663e\u5f0f\u8fde\u63a5\uff09\uff1a<\/strong><\/li>\n<\/ul>\n\n\n\n
        SELECT employees.name, departments.department_name\n  FROM employees\n  INNER JOIN departments ON employees.department_id = departments.department_id;<\/code><\/pre>\n\n\n\n
      \u8fd9\u91cc\u7684\u8fde\u63a5\u901a\u8fc7 INNER JOIN<\/code> \u8bed\u6cd5\u663e\u5f0f\u5730\u8fde\u63a5\u4e86 employees<\/code> \u548c departments<\/code> \u8868\uff0c\u5e76\u6307\u5b9a\u4e86\u8fde\u63a5\u6761\u4ef6\u3002<\/p>\n\n\n\n
      2. \u4e3a\u4ec0\u4e48\u6df7\u5408\u9690\u5f0f\u548c\u663e\u5f0f\u8fde\u63a5\u4f1a\u5bfc\u81f4\u8bed\u6cd5\u9519\u8bef\uff1f<\/strong><\/h3>\n\n\n\n
      \u6df7\u5408\u4f7f\u7528\u9690\u5f0f\u8fde\u63a5\u548c\u663e\u5f0f\u8fde\u63a5\u901a\u5e38\u4f1a\u5bfc\u81f4 SQL \u8bed\u6cd5\u9519\u8bef\uff0c\u539f\u56e0\u6709\u4ee5\u4e0b\u51e0\u70b9\uff1a<\/p>\n\n\n\n
      a. SQL \u8bed\u6cd5\u4e0d\u4e00\u81f4\u6027<\/strong><\/h4>\n\n\n\n
      SQL \u8bed\u6cd5\u89c4\u5b9a\uff0c\u6240\u6709\u7684\u8fde\u63a5\u5e94\u5f53\u9075\u5faa\u7edf\u4e00\u7684\u89c4\u8303\u3002\u9690\u5f0f\u8fde\u63a5\u548c\u663e\u5f0f\u8fde\u63a5\u662f\u4e24\u79cd\u4e0d\u540c\u7684\u8fde\u63a5\u65b9\u5f0f\uff0c\u5b83\u4eec\u7684\u7ed3\u6784\u548c\u5904\u7406\u65b9\u5f0f\u4e5f\u6709\u6240\u4e0d\u540c\u3002\u5982\u679c\u5728\u540c\u4e00\u6761\u67e5\u8be2\u4e2d\u6df7\u5408\u4f7f\u7528\u8fd9\u4e24\u8005\uff0cSQL \u5f15\u64ce\u53ef\u80fd\u65e0\u6cd5\u6b63\u786e\u89e3\u6790\u8fde\u63a5\u6761\u4ef6\uff0c\u4ece\u800c\u5bfc\u81f4\u8bed\u6cd5\u9519\u8bef\u3002<\/p>\n\n\n\n
      b. \u8fde\u63a5\u6761\u4ef6\u7684\u6b67\u4e49\u6027<\/strong><\/h4>\n\n\n\n
      \u9690\u5f0f\u8fde\u63a5\u4f9d\u8d56\u4e8e WHERE<\/code> \u5b50\u53e5\u6765\u6307\u5b9a\u8fde\u63a5\u6761\u4ef6\uff0c\u800c\u663e\u5f0f\u8fde\u63a5\u4f9d\u8d56\u4e8e ON<\/code> \u5b50\u53e5\u3002\u5728\u540c\u4e00\u4e2a\u67e5\u8be2\u4e2d\uff0cSQL \u5f15\u64ce\u53ef\u80fd\u65e0\u6cd5\u5224\u65ad\u8fde\u63a5\u6761\u4ef6\u662f\u5426\u6b63\u786e\u5339\u914d\u6216\u662f\u5173\u8054\u5230\u6b63\u786e\u7684\u8868\uff0c\u56e0\u6b64\u4f1a\u5f15\u53d1\u8bed\u6cd5\u51b2\u7a81\u3002<\/p>\n\n\n\n
      c. \u6267\u884c\u987a\u5e8f\u7684\u95ee\u9898<\/strong><\/h4>\n\n\n\n
      \u5728\u9690\u5f0f\u8fde\u63a5\u4e2d\uff0cWHERE<\/code> \u5b50\u53e5\u4e2d\u4e0d\u4ec5\u7528\u4e8e\u8fde\u63a5\u6761\u4ef6\uff0c\u4e5f\u53ef\u80fd\u5305\u542b\u5176\u4ed6\u7684\u8fc7\u6ee4\u6761\u4ef6\u3002\u800c\u5728\u663e\u5f0f\u8fde\u63a5\u4e2d\uff0cON<\/code> \u5b50\u53e5\u4ec5\u5305\u542b\u8fde\u63a5\u6761\u4ef6\uff0c\u8fc7\u6ee4\u6761\u4ef6\u901a\u5e38\u653e\u5728 WHERE<\/code> \u5b50\u53e5\u4e2d\u3002\u5982\u679c\u5c06\u8fd9\u4e24\u8005\u6df7\u5408\u4f7f\u7528\uff0c\u53ef\u80fd\u5bfc\u81f4\u8fde\u63a5\u7684\u6267\u884c\u987a\u5e8f\u4e0d\u4e00\u81f4\uff0c\u4ece\u800c\u5f15\u53d1\u8bed\u6cd5\u9519\u8bef\u3002<\/p>\n\n\n\n
      3. \u793a\u4f8b\uff1a\u6df7\u5408\u9690\u5f0f\u548c\u663e\u5f0f\u8fde\u63a5\u5bfc\u81f4\u8bed\u6cd5\u9519\u8bef<\/strong><\/h3>\n\n\n\n
      \u5047\u8bbe\u6211\u4eec\u6709\u4e24\u4e2a\u8868\uff1aemployees<\/code> \u548c departments<\/code>\u3002\u6211\u4eec\u60f3\u8fde\u63a5\u8fd9\u4e24\u4e2a\u8868\uff0c\u4f46\u5728\u540c\u4e00\u6761\u67e5\u8be2\u4e2d\u6df7\u5408\u4e86\u9690\u5f0f\u8fde\u63a5\u548c\u663e\u5f0f\u8fde\u63a5\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u5982\u4e0b\u7684\u9519\u8bef\uff1a<\/p>\n\n\n\n
      \u9519\u8bef\u793a\u4f8b\uff1a<\/h4>\n\n\n\n
      SELECT employees.name, departments.department_name\nFROM employees, departments\nINNER JOIN locations ON departments.location_id = locations.location_id\nWHERE employees.department_id = departments.department_id;<\/code><\/pre>\n\n\n\n
      \u5728\u4e0a\u9762\u7684\u67e5\u8be2\u4e2d\uff0c\u6211\u4eec\u5148\u4f7f\u7528\u4e86\u9690\u5f0f\u8fde\u63a5\uff08FROM employees, departments<\/code>\uff09\uff0c\u7136\u540e\u53c8\u4f7f\u7528\u4e86\u663e\u5f0f\u8fde\u63a5\uff08INNER JOIN locations<\/code>\uff09\u3002\u8fd9\u79cd\u6df7\u5408\u4f7f\u7528\u4f1a\u5bfc\u81f4 SQL \u5f15\u64ce\u65e0\u6cd5\u6b63\u786e\u89e3\u6790\u67e5\u8be2\uff0c\u56e0\u4e3a\u5b83\u65e0\u6cd5\u786e\u5b9a employees<\/code> \u548c departments<\/code> \u5982\u4f55\u8fde\u63a5\uff0c\u4ee5\u53ca WHERE<\/code> \u5b50\u53e5\u4e2d\u7684\u8fde\u63a5\u6761\u4ef6\u4e0e INNER JOIN<\/code> \u7684\u8fde\u63a5\u6761\u4ef6\u5982\u4f55\u534f\u8c03\u3002<\/p>\n\n\n\n
      \u9519\u8bef\u63d0\u793a\uff1a<\/h4>\n\n\n\n
      SQL syntax error or access violation<\/code><\/pre>\n\n\n\n
      4. \u5982\u4f55\u907f\u514d\u8bed\u6cd5\u9519\u8bef\uff1f<\/strong><\/h3>\n\n\n\n
      \u4e3a\u4e86\u907f\u514d\u6df7\u5408\u9690\u5f0f\u548c\u663e\u5f0f\u8fde\u63a5\u5bfc\u81f4\u7684\u8bed\u6cd5\u9519\u8bef\uff0c\u63a8\u8350\u9075\u5faa\u4ee5\u4e0b\u505a\u6cd5\uff1a<\/p>\n\n\n\n
        \n
      • \u7edf\u4e00\u8fde\u63a5\u65b9\u5f0f<\/strong>\uff1a\u5728\u540c\u4e00\u6761\u67e5\u8be2\u4e2d\uff0c\u5e94\u8be5\u59cb\u7ec8\u4f7f\u7528\u4e00\u79cd\u8fde\u63a5\u65b9\u5f0f\uff08\u8981\u4e48\u5168\u90e8\u4f7f\u7528\u9690\u5f0f\u8fde\u63a5\uff0c\u8981\u4e48\u5168\u90e8\u4f7f\u7528\u663e\u5f0f\u8fde\u63a5\uff09\u3002\u663e\u5f0f\u8fde\u63a5\u901a\u5e38\u88ab\u8ba4\u4e3a\u662f\u66f4\u6e05\u6670\u3001\u66f4\u6613\u7ef4\u62a4\u7684\u65b9\u5f0f\uff0c\u56e0\u6b64\u5efa\u8bae\u4f18\u5148\u4f7f\u7528\u663e\u5f0f\u8fde\u63a5\u3002 \u6b63\u786e\u793a\u4f8b 1\uff08\u53ea\u4f7f\u7528\u663e\u5f0f\u8fde\u63a5\uff09\uff1a<\/strong><\/li>\n<\/ul>\n\n\n\n
          SELECT employees.name, departments.department_name\n  FROM employees\n  INNER JOIN departments ON employees.department_id = departments.department_id\n  INNER JOIN locations ON departments.location_id = locations.location_id;<\/code><\/pre>\n\n\n\n
        \u6b63\u786e\u793a\u4f8b 2\uff08\u53ea\u4f7f\u7528\u9690\u5f0f\u8fde\u63a5\uff09\uff1a<\/strong><\/p>\n\n\n\n
          SELECT employees.name, departments.department_name\n  FROM employees, departments, locations\n  WHERE employees.department_id = departments.department_id\n  AND departments.location_id = locations.location_id;<\/code><\/pre>\n\n\n\n
          \n
        • \u6e05\u6670\u533a\u5206\u8fde\u63a5\u6761\u4ef6\u548c\u8fc7\u6ee4\u6761\u4ef6<\/strong>\uff1a\u5728\u4f7f\u7528\u663e\u5f0f\u8fde\u63a5\u65f6\uff0c\u786e\u4fdd\u6240\u6709\u7684\u8fde\u63a5\u6761\u4ef6\u90fd\u653e\u5728 ON<\/code> \u5b50\u53e5\u4e2d\uff0c\u6240\u6709\u7684\u8fc7\u6ee4\u6761\u4ef6\u90fd\u653e\u5728 WHERE<\/code> \u5b50\u53e5\u4e2d\u3002\u8fd9\u6837\u53ef\u4ee5\u907f\u514d\u903b\u8f91\u6df7\u4e71\uff0c\u5e76\u786e\u4fdd\u67e5\u8be2\u7684\u53ef\u8bfb\u6027\u548c\u6b63\u786e\u6027\u3002<\/li>\n<\/ul>\n\n\n\n
          5. \u603b\u7ed3<\/strong><\/h3>\n\n\n\n
          \u5728 SQL \u67e5\u8be2\u4e2d\uff0c\u9690\u5f0f\u8fde\u63a5\u548c\u663e\u5f0f\u8fde\u63a5\u5404\u6709\u5176\u9002\u7528\u7684\u573a\u666f\uff0c\u4f46\u5b83\u4eec\u7684\u8bed\u6cd5\u548c\u6267\u884c\u987a\u5e8f\u662f\u4e0d\u540c\u7684\u3002\u5f53\u6211\u4eec\u5728\u540c\u4e00\u6761\u67e5\u8be2\u4e2d\u6df7\u5408\u4f7f\u7528\u8fd9\u4e24\u8005\u65f6\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4 SQL \u5f15\u64ce\u65e0\u6cd5\u6b63\u786e\u89e3\u6790\u67e5\u8be2\uff0c\u4ece\u800c\u5f15\u53d1\u8bed\u6cd5\u9519\u8bef\u3002\u56e0\u6b64\uff0c\u6700\u597d\u4fdd\u6301\u8fde\u63a5\u8bed\u6cd5\u7684\u4e00\u81f4\u6027\uff0c\u4f18\u5148\u4f7f\u7528\u663e\u5f0f\u8fde\u63a5\uff0c\u5e76\u786e\u4fdd\u8fde\u63a5\u6761\u4ef6\u548c\u8fc7\u6ee4\u6761\u4ef6\u6e05\u6670\u5206\u79bb\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
          \u5728 SQL \u4e2d\uff0c\u9690\u5f0f\u8fde\u63a5\uff08Implicit Join\uff09\u548c\u663e\u5f0f\u8fde\u63a5\uff08Explicit Join\uff09\u662f\u4e24\u79cd\u7528\u4e8e\u5c06\u591a\u4e2a […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35],"tags":[],"class_list":["post-963","post","type-post","status-publish","format-standard","hentry","category-mysql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/963","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=963"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/963\/revisions"}],"predecessor-version":[{"id":964,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/963\/revisions\/964"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=963"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=963"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=963"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}