{"id":1782,"date":"2025-02-18T22:36:51","date_gmt":"2025-02-18T14:36:51","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=1782"},"modified":"2025-02-18T22:36:51","modified_gmt":"2025-02-18T14:36:51","slug":"mysql-join-%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/02\/18\/mysql-join-%e8%af%a6%e8%a7%a3\/","title":{"rendered":"MySQL JOIN \u8be6\u89e3"},"content":{"rendered":"\n

\u5728 MySQL \u4e2d\uff0cJOIN<\/code>\u00a0\u7528\u4e8e\u5c06\u591a\u4e2a\u8868\u4e2d\u7684\u6570\u636e\u7ed3\u5408\u8d77\u6765\uff0c\u901a\u5e38\u662f\u6839\u636e\u67d0\u4e9b\u5217\u8fdb\u884c\u5339\u914d\u3002\u5e38\u89c1\u7684 JOIN \u7c7b\u578b\u5305\u62ec\uff1aINNER JOIN<\/code>\u3001LEFT JOIN<\/code>\u3001RIGHT JOIN<\/code>\u00a0\u548c\u00a0FULL JOIN<\/code>\uff08MySQL \u4e0d\u652f\u6301\u00a0FULL JOIN<\/code>\uff0c\u901a\u5e38\u53ef\u4ee5\u901a\u8fc7\u00a0UNION<\/code>\u00a0\u5b9e\u73b0\uff09\u3002\u63a5\u4e0b\u6765\uff0c\u6211\u5c06\u7b80\u8981\u4ecb\u7ecd\u8fd9\u4e9b JOIN \u7c7b\u578b\uff0c\u5e76\u63d0\u4f9b\u4e00\u4e9b\u5b9e\u4f8b\u3002\u6db5\u76d6\u4e86\u5982\u4f55\u5728\u547d\u4ee4\u63d0\u793a\u7b26\u4e2d\u4f7f\u7528 JOIN<\/code>\uff0c\u4ee5\u53ca\u5728 PHP \u811a\u672c\u4e2d\u4f7f\u7528 JOIN<\/code> \u7684\u65b9\u5f0f\u3002<\/p>\n\n\n\n

MySQL JOIN \u8be6\u89e3<\/h3>\n\n\n\n

\u5728 MySQL \u4e2d\uff0cJOIN<\/code> \u64cd\u4f5c\u5141\u8bb8\u6211\u4eec\u5728\u4e24\u4e2a\u6216\u591a\u4e2a\u8868\u4e4b\u95f4\u8fdb\u884c\u67e5\u8be2\uff0c\u7ed3\u5408\u4e0d\u540c\u8868\u7684\u6570\u636e\u3002\u5e38\u89c1\u7684 JOIN<\/code> \u7c7b\u578b\u6709\uff1a<\/p>\n\n\n\n

    \n
  • INNER JOIN<\/code><\/li>\n\n\n\n
  • LEFT JOIN<\/code>\uff08\u6216 LEFT OUTER JOIN<\/code>\uff09<\/li>\n\n\n\n
  • RIGHT JOIN<\/code>\uff08\u6216 RIGHT OUTER JOIN<\/code>\uff09<\/li>\n\n\n\n
  • CROSS JOIN<\/code><\/li>\n\n\n\n
  • FULL OUTER JOIN<\/code>\uff08\u9700\u8981\u901a\u8fc7 UNION<\/code> \u5b9e\u73b0\uff09<\/li>\n<\/ul>\n\n\n\n

    1. INNER JOIN<\/strong><\/h3>\n\n\n\n

    INNER JOIN<\/code> \u8fd4\u56de\u4e24\u4e2a\u8868\u4e2d\u7b26\u5408\u5339\u914d\u6761\u4ef6\u7684\u6240\u6709\u884c\u3002\u5982\u679c\u67d0\u4e2a\u8868\u4e2d\u7684\u884c\u5728\u53e6\u4e00\u4e2a\u8868\u4e2d\u627e\u4e0d\u5230\u5339\u914d\uff0c\u5b83\u5c06\u88ab\u6392\u9664\u5728\u7ed3\u679c\u4e4b\u5916\u3002<\/p>\n\n\n\n

    \u53c2\u6570\u8bf4\u660e\uff1a<\/h4>\n\n\n\n
      \n
    • ON<\/code> \u540e\u9762\u8ddf\u7684\u662f\u8fde\u63a5\u6761\u4ef6\uff0c\u901a\u5e38\u662f\u4e24\u4e2a\u8868\u4e2d\u76f8\u540c\u5b57\u6bb5\u7684\u6bd4\u8f83\u3002<\/li>\n<\/ul>\n\n\n\n

      \u547d\u4ee4\u884c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n

      \u5047\u8bbe\u6211\u4eec\u6709\u4e24\u4e2a\u8868\uff1aemployees<\/code> \u548c departments<\/code>\uff0c\u67e5\u8be2\u6240\u6709\u6709\u90e8\u95e8\u7684\u5458\u5de5\uff1a<\/p>\n\n\n\n

      SELECT employees.emp_name, departments.dept_name\nFROM employees\nINNER JOIN departments ON employees.dept_id = departments.dept_id;<\/code><\/pre>\n\n\n\n
      \u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n
        \n
      • employees.emp_name<\/code>\uff1a\u6211\u4eec\u8981\u67e5\u8be2\u7684\u5b57\u6bb5\uff0cemp_name<\/code> \u662f\u5458\u5de5\u7684\u540d\u5b57\u3002<\/li>\n\n\n\n
      • departments.dept_name<\/code>\uff1a\u6211\u4eec\u8981\u67e5\u8be2\u7684\u5b57\u6bb5\uff0cdept_name<\/code> \u662f\u90e8\u95e8\u7684\u540d\u79f0\u3002<\/li>\n\n\n\n
      • employees.dept_id<\/code> \u548c departments.dept_id<\/code>\uff1a\u8fd9\u4e24\u4e2a\u5b57\u6bb5\u662f\u7528\u4e8e\u5339\u914d\u5458\u5de5\u548c\u90e8\u95e8\u7684\u5b57\u6bb5\u3002<\/li>\n<\/ul>\n\n\n\n
        PHP \u811a\u672c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
        \u5728 PHP \u4e2d\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7 mysqli<\/code> \u6216 PDO<\/code> \u6269\u5c55\u6765\u8fde\u63a5\u6570\u636e\u5e93\u5e76\u6267\u884c\u67e5\u8be2\u3002\u4ee5\u4e0b\u662f\u4f7f\u7528 mysqli<\/code> \u8fde\u63a5 MySQL \u5e76\u6267\u884c INNER JOIN<\/code> \u67e5\u8be2\u7684\u4f8b\u5b50\uff1a<\/p>\n\n\n\n
        <?php\n\/\/ \u521b\u5efa\u6570\u636e\u5e93\u8fde\u63a5\n$mysqli = new mysqli(\"localhost\", \"username\", \"password\", \"database_name\");\n\n\/\/ \u68c0\u67e5\u8fde\u63a5\u662f\u5426\u6210\u529f\nif ($mysqli->connect_error) {\n    die(\"Connection failed: \" . $mysqli->connect_error);\n}\n\n\/\/ \u6267\u884c\u67e5\u8be2\n$sql = \"SELECT employees.emp_name, departments.dept_name\n        FROM employees\n        INNER JOIN departments ON employees.dept_id = departments.dept_id\";\n$result = $mysqli->query($sql);\n\n\/\/ \u8f93\u51fa\u67e5\u8be2\u7ed3\u679c\nif ($result->num_rows > 0) {\n    while($row = $result->fetch_assoc()) {\n        echo \"Employee: \" . $row[\"emp_name\"]. \" - Department: \" . $row[\"dept_name\"]. \"<br>\";\n    }\n} else {\n    echo \"0 results\";\n}\n\n\/\/ \u5173\u95ed\u8fde\u63a5\n$mysqli->close();\n?><\/code><\/pre>\n\n\n\n
        \u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n
          \n
        • $mysqli->query($sql)<\/code>\uff1a\u6267\u884c\u67e5\u8be2 SQL\u3002<\/li>\n\n\n\n
        • $result->fetch_assoc()<\/code>\uff1a\u8fd4\u56de\u5f53\u524d\u884c\u4f5c\u4e3a\u5173\u8054\u6570\u7ec4\uff0c\u53ef\u4ee5\u901a\u8fc7\u5b57\u6bb5\u540d\u79f0\u8bbf\u95ee\u6570\u636e\u3002<\/li>\n<\/ul>\n\n\n\n
          2. LEFT JOIN<\/strong>\uff08\u6216 LEFT OUTER JOIN\uff09<\/h3>\n\n\n\n
          LEFT JOIN<\/code> \u8fd4\u56de\u5de6\u8868\uff08employees<\/code>\uff09\u4e2d\u7684\u6240\u6709\u884c\uff0c\u5373\u4f7f\u53f3\u8868\uff08departments<\/code>\uff09\u4e2d\u6ca1\u6709\u5339\u914d\u7684\u884c\u3002\u5982\u679c\u6ca1\u6709\u5339\u914d\uff0c\u5219\u53f3\u8868\u7684\u5b57\u6bb5\u4e3a NULL<\/code>\u3002<\/p>\n\n\n\n
          \u547d\u4ee4\u884c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
          SELECT employees.emp_name, departments.dept_name\nFROM employees\nLEFT JOIN departments ON employees.dept_id = departments.dept_id;<\/code><\/pre>\n\n\n\n
          \u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n
            \n
          • LEFT JOIN<\/code>\uff1a\u786e\u4fdd\u8fd4\u56de\u5de6\u8868\uff08employees<\/code>\uff09\u7684\u6240\u6709\u884c\u3002<\/li>\n<\/ul>\n\n\n\n
            PHP \u811a\u672c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            <?php\n\/\/ \u521b\u5efa\u6570\u636e\u5e93\u8fde\u63a5\n$mysqli = new mysqli(\"localhost\", \"username\", \"password\", \"database_name\");\n\n\/\/ \u68c0\u67e5\u8fde\u63a5\u662f\u5426\u6210\u529f\nif ($mysqli->connect_error) {\n    die(\"Connection failed: \" . $mysqli->connect_error);\n}\n\n\/\/ \u6267\u884c\u67e5\u8be2\n$sql = \"SELECT employees.emp_name, departments.dept_name\n        FROM employees\n        LEFT JOIN departments ON employees.dept_id = departments.dept_id\";\n$result = $mysqli->query($sql);\n\n\/\/ \u8f93\u51fa\u67e5\u8be2\u7ed3\u679c\nif ($result->num_rows > 0) {\n    while($row = $result->fetch_assoc()) {\n        echo \"Employee: \" . $row[\"emp_name\"]. \" - Department: \" . $row[\"dept_name\"]. \"<br>\";\n    }\n} else {\n    echo \"0 results\";\n}\n\n\/\/ \u5173\u95ed\u8fde\u63a5\n$mysqli->close();\n?><\/code><\/pre>\n\n\n\n
            3. RIGHT JOIN<\/strong>\uff08\u6216 RIGHT OUTER JOIN\uff09<\/h3>\n\n\n\n
            RIGHT JOIN<\/code> \u8fd4\u56de\u53f3\u8868\uff08departments<\/code>\uff09\u4e2d\u7684\u6240\u6709\u884c\u3002\u5982\u679c\u5de6\u8868\uff08employees<\/code>\uff09\u4e2d\u6ca1\u6709\u5339\u914d\u7684\u884c\uff0c\u5219\u5de6\u8868\u7684\u5b57\u6bb5\u4e3a NULL<\/code>\u3002<\/p>\n\n\n\n
            \u547d\u4ee4\u884c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            SELECT employees.emp_name, departments.dept_name\nFROM employees\nRIGHT JOIN departments ON employees.dept_id = departments.dept_id;<\/code><\/pre>\n\n\n\n
            PHP \u811a\u672c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            <?php\n\/\/ \u521b\u5efa\u6570\u636e\u5e93\u8fde\u63a5\n$mysqli = new mysqli(\"localhost\", \"username\", \"password\", \"database_name\");\n\n\/\/ \u68c0\u67e5\u8fde\u63a5\u662f\u5426\u6210\u529f\nif ($mysqli->connect_error) {\n    die(\"Connection failed: \" . $mysqli->connect_error);\n}\n\n\/\/ \u6267\u884c\u67e5\u8be2\n$sql = \"SELECT employees.emp_name, departments.dept_name\n        FROM employees\n        RIGHT JOIN departments ON employees.dept_id = departments.dept_id\";\n$result = $mysqli->query($sql);\n\n\/\/ \u8f93\u51fa\u67e5\u8be2\u7ed3\u679c\nif ($result->num_rows > 0) {\n    while($row = $result->fetch_assoc()) {\n        echo \"Employee: \" . $row[\"emp_name\"]. \" - Department: \" . $row[\"dept_name\"]. \"<br>\";\n    }\n} else {\n    echo \"0 results\";\n}\n\n\/\/ \u5173\u95ed\u8fde\u63a5\n$mysqli->close();\n?><\/code><\/pre>\n\n\n\n
            4. CROSS JOIN<\/strong><\/h3>\n\n\n\n
            CROSS JOIN<\/code> \u8fd4\u56de\u4e24\u4e2a\u8868\u7684\u7b1b\u5361\u5c14\u79ef\uff0c\u5373\u6bcf\u4e2a\u5de6\u8868\u7684\u884c\u90fd\u4e0e\u6bcf\u4e2a\u53f3\u8868\u7684\u884c\u7ec4\u5408\u3002<\/p>\n\n\n\n
            \u547d\u4ee4\u884c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            SELECT employees.emp_name, departments.dept_name\nFROM employees\nCROSS JOIN departments;<\/code><\/pre>\n\n\n\n
            PHP \u811a\u672c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            <?php\n\/\/ \u521b\u5efa\u6570\u636e\u5e93\u8fde\u63a5\n$mysqli = new mysqli(\"localhost\", \"username\", \"password\", \"database_name\");\n\n\/\/ \u68c0\u67e5\u8fde\u63a5\u662f\u5426\u6210\u529f\nif ($mysqli->connect_error) {\n    die(\"Connection failed: \" . $mysqli->connect_error);\n}\n\n\/\/ \u6267\u884c\u67e5\u8be2\n$sql = \"SELECT employees.emp_name, departments.dept_name\n        FROM employees\n        CROSS JOIN departments\";\n$result = $mysqli->query($sql);\n\n\/\/ \u8f93\u51fa\u67e5\u8be2\u7ed3\u679c\nif ($result->num_rows > 0) {\n    while($row = $result->fetch_assoc()) {\n        echo \"Employee: \" . $row[\"emp_name\"]. \" - Department: \" . $row[\"dept_name\"]. \"<br>\";\n    }\n} else {\n    echo \"0 results\";\n}\n\n\/\/ \u5173\u95ed\u8fde\u63a5\n$mysqli->close();\n?><\/code><\/pre>\n\n\n\n
            5. FULL OUTER JOIN<\/strong>\uff08\u901a\u8fc7 UNION<\/code> \u5b9e\u73b0\uff09<\/h3>\n\n\n\n
            MySQL \u4e0d\u76f4\u63a5\u652f\u6301 FULL OUTER JOIN<\/code>\uff0c\u4f46\u53ef\u4ee5\u901a\u8fc7\u7ed3\u5408 LEFT JOIN<\/code> \u548c RIGHT JOIN<\/code> \u6765\u5b9e\u73b0\u7c7b\u4f3c\u7684\u6548\u679c\u3002<\/p>\n\n\n\n
            \u547d\u4ee4\u884c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            SELECT employees.emp_name, departments.dept_name\nFROM employees\nLEFT JOIN departments ON employees.dept_id = departments.dept_id\nUNION\nSELECT employees.emp_name, departments.dept_name\nFROM employees\nRIGHT JOIN departments ON employees.dept_id = departments.dept_id;<\/code><\/pre>\n\n\n\n
            PHP \u811a\u672c\u4f7f\u7528\uff1a<\/h4>\n\n\n\n
            <?php\n\/\/ \u521b\u5efa\u6570\u636e\u5e93\u8fde\u63a5\n$mysqli = new mysqli(\"localhost\", \"username\", \"password\", \"database_name\");\n\n\/\/ \u68c0\u67e5\u8fde\u63a5\u662f\u5426\u6210\u529f\nif ($mysqli->connect_error) {\n    die(\"Connection failed: \" . $mysqli->connect_error);\n}\n\n\/\/ \u6267\u884c\u67e5\u8be2\n$sql = \"SELECT employees.emp_name, departments.dept_name\n        FROM employees\n        LEFT JOIN departments ON employees.dept_id = departments.dept_id\n        UNION\n        SELECT employees.emp_name, departments.dept_name\n        FROM employees\n        RIGHT JOIN departments ON employees.dept_id = departments.dept_id\";\n$result = $mysqli->query($sql);\n\n\/\/ \u8f93\u51fa\u67e5\u8be2\u7ed3\u679c\nif ($result->num_rows > 0) {\n    while($row = $result->fetch_assoc()) {\n        echo \"Employee: \" . $row[\"emp_name\"]. \" - Department: \" . $row[\"dept_name\"]. \"<br>\";\n    }\n} else {\n    echo \"0 results\";\n}\n\n\/\/ \u5173\u95ed\u8fde\u63a5\n$mysqli->close();\n?><\/code><\/pre>\n\n\n\n
            \u603b\u7ed3<\/h3>\n\n\n\n
              \n
            • INNER JOIN<\/code><\/strong>\uff1a\u8fd4\u56de\u4e24\u4e2a\u8868\u4e2d\u5339\u914d\u7684\u8bb0\u5f55\u3002<\/li>\n\n\n\n
            • LEFT JOIN<\/code><\/strong>\uff1a\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u5373\u4f7f\u53f3\u8868\u4e2d\u6ca1\u6709\u5339\u914d\u7684\u8bb0\u5f55\u3002<\/li>\n\n\n\n
            • RIGHT JOIN<\/code><\/strong>\uff1a\u8fd4\u56de\u53f3\u8868\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u5373\u4f7f\u5de6\u8868\u4e2d\u6ca1\u6709\u5339\u914d\u7684\u8bb0\u5f55\u3002<\/li>\n\n\n\n
            • CROSS JOIN<\/code><\/strong>\uff1a\u8fd4\u56de\u4e24\u4e2a\u8868\u7684\u7b1b\u5361\u5c14\u79ef\uff0c\u6bcf\u4e2a\u5de6\u8868\u7684\u884c\u4e0e\u6bcf\u4e2a\u53f3\u8868\u7684\u884c\u7ec4\u5408\u3002<\/li>\n\n\n\n
            • FULL OUTER JOIN<\/code><\/strong>\uff1aMySQL \u4e0d\u76f4\u63a5\u652f\u6301\uff0c\u4f7f\u7528 UNION<\/code> \u6765\u5b9e\u73b0\u3002<\/li>\n<\/ul>\n\n\n\n
              \u8fd9\u4e9b JOIN<\/code> \u64cd\u4f5c\u5728\u547d\u4ee4\u884c\u548c PHP \u4e2d\u7684\u7528\u6cd5\u57fa\u672c\u4e00\u81f4\uff0c\u53ea\u662f\u5728 PHP \u4e2d\u901a\u8fc7\u6570\u636e\u5e93\u8fde\u63a5\u548c\u67e5\u8be2\u6267\u884c\u6765\u83b7\u53d6\u7ed3\u679c\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
              \u5728 MySQL \u4e2d\uff0cJOIN\u00a0\u7528\u4e8e\u5c06\u591a\u4e2a\u8868\u4e2d\u7684\u6570\u636e\u7ed3\u5408\u8d77\u6765\uff0c\u901a\u5e38\u662f\u6839\u636e\u67d0\u4e9b\u5217\u8fdb\u884c\u5339\u914d\u3002\u5e38\u89c1\u7684 JOIN \u7c7b\u578b\u5305 […]<\/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-1782","post","type-post","status-publish","format-standard","hentry","category-mysql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1782","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=1782"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1782\/revisions"}],"predecessor-version":[{"id":1783,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1782\/revisions\/1783"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=1782"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=1782"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=1782"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}