{"id":2350,"date":"2025-03-04T19:26:35","date_gmt":"2025-03-04T11:26:35","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2350"},"modified":"2025-03-04T19:26:35","modified_gmt":"2025-03-04T11:26:35","slug":"sqlite-join","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/04\/sqlite-join\/","title":{"rendered":"SQLite\u00a0Join"},"content":{"rendered":"\n
\n

\u5728 SQLite \u4e2d\uff0cJOIN<\/strong> \u7528\u4e8e\u5728\u67e5\u8be2\u65f6\u5408\u5e76\u591a\u4e2a\u8868\u7684\u6570\u636e<\/strong>\uff0c\u901a\u5e38\u57fa\u4e8e\u516c\u5171\u5217<\/strong>\uff08\u5982\u5916\u952e\uff09\u3002SQLite \u652f\u6301\u591a\u79cd JOIN<\/strong> \u64cd\u4f5c\uff0c\u5305\u62ec\uff1a<\/p>\n<\/blockquote>\n\n\n\n

    \n
  1. INNER JOIN<\/strong>\uff08\u5185\u8fde\u63a5\uff09<\/li>\n\n\n\n
  2. LEFT JOIN<\/strong>\uff08\u5de6\u8fde\u63a5\uff09<\/li>\n\n\n\n
  3. RIGHT JOIN<\/strong>\uff08\u53f3\u8fde\u63a5\uff0cSQLite \u4e0d\u76f4\u63a5\u652f\u6301\uff09<\/li>\n\n\n\n
  4. FULL OUTER JOIN<\/strong>\uff08\u5168\u5916\u8fde\u63a5\uff0cSQLite \u4e0d\u76f4\u63a5\u652f\u6301\uff09<\/li>\n\n\n\n
  5. CROSS JOIN<\/strong>\uff08\u4ea4\u53c9\u8fde\u63a5\uff09<\/li>\n\n\n\n
  6. SELF JOIN<\/strong>\uff08\u81ea\u8fde\u63a5\uff09<\/li>\n<\/ol>\n\n\n\n
    \n\n\n\n

    1. INNER JOIN\uff08\u5185\u8fde\u63a5\uff09<\/strong><\/h2>\n\n\n\n

    \u4f5c\u7528<\/strong>\uff1a\u4ec5\u8fd4\u56de\u4e24\u4e2a\u8868\u4e2d\u5339\u914d\u7684\u884c\u3002<\/p>\n\n\n\n

    \u793a\u4f8b\uff1a\u67e5\u8be2\u8ba2\u5355\u7684\u7528\u6237\u4fe1\u606f<\/strong><\/h3>\n\n\n\n
    CREATE TABLE users (\n    id INTEGER PRIMARY KEY,\n    name TEXT\n);\n\nCREATE TABLE orders (\n    order_id INTEGER PRIMARY KEY,\n    user_id INTEGER,\n    product TEXT,\n    FOREIGN KEY (user_id) REFERENCES users(id)\n);\n\nINSERT INTO users (id, name) VALUES (1, 'Alice'), (2, 'Bob');\nINSERT INTO orders (order_id, user_id, product) VALUES (101, 1, 'Laptop'), (102, 2, 'Phone');\n\nSELECT users.name, orders.product\nFROM users\nINNER JOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c<\/strong><\/p>\n\n\n\n
    name    | product\n-------------------\nAlice   | Laptop\nBob     | Phone<\/code><\/pre>\n\n\n\n
    \u89e3\u91ca<\/strong>\uff1a<\/p>\n\n\n\n
      \n
    • INNER JOIN<\/code> \u53ea\u8fd4\u56de users.id<\/code> \u548c orders.user_id<\/code> \u5339\u914d<\/strong> \u7684\u884c\u3002<\/li>\n<\/ul>\n\n\n\n
      \n\n\n\n
      2. LEFT JOIN\uff08\u5de6\u8fde\u63a5\uff09<\/strong><\/h2>\n\n\n\n
      \u4f5c\u7528<\/strong>\uff1a\u8fd4\u56de \u5de6\u8868<\/strong> \u7684\u6240\u6709\u884c\uff0c\u5373\u4f7f\u53f3\u8868\u6ca1\u6709\u5339\u914d\u9879\uff0c\u53f3\u8868\u6570\u636e\u4f1a\u4ee5 NULL<\/code> \u586b\u5145\u3002<\/p>\n\n\n\n
      \u793a\u4f8b\uff1a\u67e5\u8be2\u6240\u6709\u7528\u6237\u7684\u8ba2\u5355\u4fe1\u606f\uff08\u5305\u62ec\u672a\u4e0b\u5355\u7684\u7528\u6237\uff09<\/strong><\/h3>\n\n\n\n
      SELECT users.name, orders.product\nFROM users\nLEFT JOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c<\/strong><\/p>\n\n\n\n
      name    | product\n-------------------\nAlice   | Laptop\nBob     | Phone\nCharlie | NULL<\/code><\/pre>\n\n\n\n
      \u89e3\u91ca<\/strong>\uff1a<\/p>\n\n\n\n
        \n
      • LEFT JOIN<\/code> \u8fd4\u56de users<\/code> \u6240\u6709\u884c<\/strong>\uff0c\u5373\u4f7f orders<\/code> \u6ca1\u6709\u5339\u914d\u7684\u6570\u636e\uff08Charlie<\/code> \u6ca1\u6709\u8ba2\u5355\uff0cproduct<\/code> \u663e\u793a NULL<\/code>\uff09\u3002<\/li>\n<\/ul>\n\n\n\n
        \n\n\n\n
        3. RIGHT JOIN\uff08\u53f3\u8fde\u63a5\uff0cSQLite \u4e0d\u652f\u6301\uff09<\/strong><\/h2>\n\n\n\n
        SQLite \u4e0d\u652f\u6301<\/strong> RIGHT JOIN<\/code>\uff0c\u4f46\u53ef\u4ee5\u901a\u8fc7\u4ea4\u6362\u8868\u7684 LEFT JOIN<\/code> \u6765\u5b9e\u73b0\uff1a<\/p>\n\n\n\n
        SELECT users.name, orders.product\nFROM orders\nLEFT JOIN users ON orders.user_id = users.id;<\/code><\/pre>\n\n\n\n
        \u8fd9\u6837\u5c31\u6a21\u62df\u4e86 RIGHT JOIN<\/code><\/strong>\u3002<\/p>\n\n\n\n
        \n\n\n\n
        4. FULL OUTER JOIN\uff08\u5168\u5916\u8fde\u63a5\uff0cSQLite \u4e0d\u652f\u6301\uff09<\/strong><\/h2>\n\n\n\n
        SQLite \u4e0d\u652f\u6301<\/strong> FULL OUTER JOIN<\/code>\uff0c\u4f46\u53ef\u4ee5\u7528 LEFT JOIN<\/code> + UNION<\/code> + RIGHT JOIN<\/code> \u7ec4\u5408\uff1a<\/p>\n\n\n\n
        SELECT users.name, orders.product\nFROM users\nLEFT JOIN orders ON users.id = orders.user_id\n\nUNION\n\nSELECT users.name, orders.product\nFROM users\nRIGHT JOIN orders ON users.id = orders.user_id;<\/code><\/pre>\n\n\n\n
        \u8fd9\u6837\u80fd\u8fd4\u56de\u6240\u6709\u5339\u914d\u548c\u4e0d\u5339\u914d\u7684\u884c<\/strong>\u3002<\/p>\n\n\n\n
        \n\n\n\n
        5. CROSS JOIN\uff08\u4ea4\u53c9\u8fde\u63a5\uff09<\/strong><\/h2>\n\n\n\n
        \u4f5c\u7528<\/strong>\uff1a\u8fd4\u56de\u4e24\u5f20\u8868\u7684\u7b1b\u5361\u5c14\u79ef<\/strong>\uff08\u5373\u6bcf\u4e00\u884c\u4e0e\u53e6\u4e00\u8868\u7684\u6240\u6709\u884c\u7ec4\u5408\uff09\u3002<\/p>\n\n\n\n
        \u793a\u4f8b<\/strong><\/h3>\n\n\n\n
        SELECT users.name, orders.product\nFROM users\nCROSS JOIN orders;<\/code><\/pre>\n\n\n\n
        \u5982\u679c users<\/code> \u6709 2 \u884c\uff0corders<\/code> \u6709 3 \u884c\uff0c\u7ed3\u679c\u5c06\u662f 2 \u00d7 3 = 6<\/code> \u884c\u3002<\/p>\n\n\n\n
        \n\n\n\n
        6. SELF JOIN\uff08\u81ea\u8fde\u63a5\uff09<\/strong><\/h2>\n\n\n\n
        \u4f5c\u7528<\/strong>\uff1a\u5728\u540c\u4e00\u5f20\u8868<\/strong>\u4e0a\u505a\u8fde\u63a5\uff0c\u901a\u5e38\u7528\u4e8e\u5c42\u7ea7\u7ed3\u6784<\/strong>\u67e5\u8be2\uff08\u5982\u5458\u5de5-\u7ecf\u7406\u5173\u7cfb\uff09\u3002<\/p>\n\n\n\n
        \u793a\u4f8b\uff1a\u67e5\u8be2\u5458\u5de5\u7684\u4e0a\u7ea7<\/strong><\/h3>\n\n\n\n
        CREATE TABLE employees (\n    id INTEGER PRIMARY KEY,\n    name TEXT,\n    manager_id INTEGER -- \u8be5\u5458\u5de5\u7684\u4e0a\u7ea7 ID\n);\n\nINSERT INTO employees (id, name, manager_id) VALUES\n(1, 'CEO', NULL),\n(2, 'Manager A', 1),\n(3, 'Manager B', 1),\n(4, 'Employee X', 2),\n(5, 'Employee Y', 2);\n\nSELECT e1.name AS employee, e2.name AS manager\nFROM employees e1\nLEFT JOIN employees e2 ON e1.manager_id = e2.id;<\/code><\/pre>\n\n\n\n
        \u7ed3\u679c<\/strong><\/p>\n\n\n\n
        employee    | manager\n---------------------\nCEO         | NULL\nManager A   | CEO\nManager B   | CEO\nEmployee X  | Manager A\nEmployee Y  | Manager A<\/code><\/pre>\n\n\n\n
        \n\n\n\n
        \u603b\u7ed3<\/strong><\/h2>\n\n\n\n
        JOIN \u7c7b\u578b<\/th>\u4f5c\u7528<\/th><\/tr><\/thead>
        INNER JOIN<\/td>\u8fd4\u56de\u4e24\u4e2a\u8868\u4e2d\u5339\u914d\u7684\u884c<\/td><\/tr>
        LEFT JOIN<\/td>\u8fd4\u56de\u5de6\u8868\u6240\u6709\u884c\uff0c\u53f3\u8868\u65e0\u5339\u914d\u5219 NULL<\/code><\/td><\/tr>
        RIGHT JOIN<\/td>SQLite \u4e0d\u652f\u6301<\/strong>\uff0c\u53ef\u7528 LEFT JOIN<\/code> \u6a21\u62df<\/td><\/tr>
        FULL JOIN<\/td>SQLite \u4e0d\u652f\u6301<\/strong>\uff0c\u53ef\u7528 UNION<\/code> \u7ec4\u5408 LEFT JOIN<\/code> \u548c RIGHT JOIN<\/code><\/td><\/tr>
        CROSS JOIN<\/td>\u8fd4\u56de\u4e24\u8868\u7684\u7b1b\u5361\u5c14\u79ef<\/strong><\/td><\/tr>
        SELF JOIN<\/td>\u5728\u540c\u4e00\u8868\u4e2d\u505a JOIN<\/code>\uff0c\u901a\u5e38\u7528\u4e8e\u5c42\u7ea7\u6570\u636e<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
        \n\n\n\n
        \u5982\u679c\u4f60\u6709\u66f4\u5177\u4f53\u7684 JOIN<\/code> \u4f7f\u7528\u573a\u666f\uff0c\u6b22\u8fce\u63d0\u95ee\uff01 \ud83d\ude0a<\/p>\n\n\n\n
        \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
        \u5728 SQLite \u4e2d\uff0cJOIN \u7528\u4e8e\u5728\u67e5\u8be2\u65f6\u5408\u5e76\u591a\u4e2a\u8868\u7684\u6570\u636e\uff0c\u901a\u5e38\u57fa\u4e8e\u516c\u5171\u5217\uff08\u5982\u5916\u952e\uff09\u3002SQLite \u652f\u6301\u591a\u79cd […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[76],"tags":[],"class_list":["post-2350","post","type-post","status-publish","format-standard","hentry","category-sqlite"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2350","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=2350"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2350\/revisions"}],"predecessor-version":[{"id":2351,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2350\/revisions\/2351"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2350"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2350"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2350"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}