{"id":199655,"date":"2025-05-06T09:19:38","date_gmt":"2025-05-06T01:19:38","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199655\/"},"modified":"2025-05-06T09:19:38","modified_gmt":"2025-05-06T01:19:38","slug":"%e4%bd%bf%e7%94%a8mysql%e4%b8%ad%e7%9a%84exists%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199655\/","title":{"rendered":"\u4f7f\u7528MYSQL\u4e2d\u7684EXISTS\u51fd\u6570"},"content":{"rendered":"

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

\u4f7f\u7528MYSQL\u4e2d\u7684EXISTS\u51fd\u6570<\/h1>\n

\u77e5\u8bc6\u70b9\u638c\u63e1\u4e86\uff0c\u8fd8\u9700\u8981\u4e0d\u65ad\u7ec3\u4e60\u624d\u80fd\u719f\u7ec3\u8fd0\u7528\u3002\u4e0b\u9762\u4e3b\u673a\u5b9d\u8d1d\u7ed9\u5927\u5bb6\u5e26\u6765\u4e00\u4e2a\u6570\u636e\u5e93\u5f00\u53d1\u5b9e\u6218\uff0c\u624b\u628a\u624b\u6559\u5927\u5bb6\u5b66\u4e60\u300a\u4f7f\u7528MYSQL\u4e2d\u7684EXISTS\u51fd\u6570\u300b\uff0c\u5728\u5b9e\u73b0\u529f\u80fd\u7684\u8fc7\u7a0b\u4e2d\u4e5f\u5e26\u5927\u5bb6\u91cd\u65b0\u6e29\u4e60\u76f8\u5173\u77e5\u8bc6\u70b9\uff0c\u6e29\u6545\u800c\u77e5\u65b0\uff0c\u56de\u5934\u770b\u770b\u8bf4\u4e0d\u5b9a\u53c8\u6709\u4e0d\u4e00\u6837\u7684\u611f\u609f\uff01<\/p>\n

MYSQL\u4e2dEXISTS\u7684\u7528\u6cd5\uff0c\u9644\u5e26\u4ee3\u7801\u793a\u4f8b<\/p>\n

\u5728MYSQL\u6570\u636e\u5e93\u4e2d\uff0cEXISTS\u662f\u4e00\u4e2a\u975e\u5e38\u6709\u7528\u7684\u64cd\u4f5c\u7b26\uff0c\u7528\u4e8e\u5224\u65ad\u4e00\u4e2a\u5b50\u67e5\u8be2\u662f\u5426\u81f3\u5c11\u8fd4\u56de\u4e86\u4e00\u884c\u6570\u636e\u3002\u5b83\u901a\u5e38\u4e0eWHERE\u5b50\u53e5\u4e00\u8d77\u4f7f\u7528\uff0c\u4ee5\u4fbf\u6839\u636e\u5b50\u67e5\u8be2\u7684\u7ed3\u679c\u7b5b\u9009\u51fa\u6ee1\u8db3\u6761\u4ef6\u7684\u6570\u636e\u3002<\/p>\n

\u4f7f\u7528EXISTS\u9700\u8981\u6ce8\u610f\u4ee5\u4e0b\u51e0\u70b9\uff1a<\/p>\n

    \n
  1. EXISTS\u6761\u4ef6\u4e0d\u5173\u5fc3\u5b50\u67e5\u8be2\u8fd4\u56de\u7684\u5177\u4f53\u6570\u636e\uff0c\u53ea\u5173\u5fc3\u662f\u5426\u6709\u6570\u636e\u8fd4\u56de\u3002<\/li>\n
  2. EXISTS\u6761\u4ef6\u53ef\u4ee5\u4e0e\u5176\u4ed6\u7684\u6761\u4ef6\u7ed3\u5408\u4f7f\u7528\uff0c\u4ee5\u8fdb\u4e00\u6b65\u9650\u5b9a\u6570\u636e\u7684\u9009\u62e9\u8303\u56f4\u3002<\/li>\n<\/ol>\n

    \u4e0b\u9762\u6211\u4eec\u901a\u8fc7\u4e00\u4e9b\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b\u6765\u8bf4\u660eEXISTS\u7684\u7528\u6cd5\u3002<\/p>\n

    \u5047\u8bbe\u6211\u4eec\u6709\u4e24\u4e2a\u8868\uff1a\u5546\u54c1\u8868\uff08products\uff09\u548c\u8ba2\u5355\u8868\uff08orders\uff09\u3002<\/p>\n

    \u5546\u54c1\u8868\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n

    CREATE TABLE products (\n  id INT,\n  name VARCHAR(50),\n  price FLOAT\n);<\/pre>\n
    \u8ba2\u5355\u8868\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n
    CREATE TABLE orders (\n  id INT,\n  product_id INT,\n  quantity INT\n);<\/pre>\n
    \u73b0\u5728\uff0c\u6211\u4eec\u60f3\u627e\u51fa\u6240\u6709\u6709\u8ba2\u5355\u7684\u5546\u54c1\u3002\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528EXISTS\u5b50\u67e5\u8be2\u6765\u5b9e\u73b0\u8fd9\u4e2a\u76ee\u6807\u3002<\/p>\n
    SELECT * FROM products p\nWHERE EXISTS (\n  SELECT 1 FROM orders o\n  WHERE o.product_id = p.id\n);<\/pre>\n
    \u5728\u4e0a\u8ff0\u4f8b\u5b50\u4e2d\uff0c\u5b50\u67e5\u8be2SELECT 1 FROM orders o WHERE o.product_id = p.id<\/code>\u5c06\u8fd4\u56de\u4e00\u4e2a\u7ed3\u679c\u96c6\uff0c\u8fd9\u4e2a\u7ed3\u679c\u96c6\u81f3\u5c11\u5305\u542b\u4e00\u884c\u6570\u636e\uff0c\u8868\u793a\u6709\u8ba2\u5355\u4e0e\u5f53\u524d\u5546\u54c1\u76f8\u5173\u8054\u3002\u5728\u5916\u5c42\u67e5\u8be2\u4e2d\uff0c\u6211\u4eec\u4f7f\u7528\u4e86EXISTS\u6761\u4ef6\uff0c\u5982\u679c\u5b50\u67e5\u8be2\u8fd4\u56de\u81f3\u5c11\u4e00\u884c\u6570\u636e\uff0c\u5219\u6b64\u6761\u8bb0\u5f55\u4f1a\u88ab\u8fd4\u56de\u3002<\/p>\n
    \u6211\u4eec\u4e5f\u53ef\u4ee5\u4f7f\u7528EXISTS\u4e0e\u5176\u4ed6\u6761\u4ef6\u7ed3\u5408\u6765\u8fdb\u4e00\u6b65\u7b5b\u9009\u6570\u636e\u3002\u6bd4\u5982\uff0c\u6211\u4eec\u60f3\u627e\u51fa\u6240\u6709\u4ef7\u683c\u4f4e\u4e8e100\u7684\u6709\u8ba2\u5355\u7684\u5546\u54c1\u3002<\/p>\n
    SELECT * FROM products p\nWHERE price < 100\nAND EXISTS (\n  SELECT 1 FROM orders o\n  WHERE o.product_id = p.id\n);<\/pre>\n
    \u4e0a\u8ff0\u4ee3\u7801\u4e2d\uff0c\u6211\u4eec\u5728\u5916\u5c42\u67e5\u8be2\u7684WHERE\u5b50\u53e5\u4e2d\u589e\u52a0\u4e86price < 100<\/code>\u7684\u6761\u4ef6\uff0c\u610f\u5473\u7740\u53ea\u6709\u4ef7\u683c\u4f4e\u4e8e100\u7684\u5546\u54c1\u624d\u4f1a\u88ab\u8fd4\u56de\u3002<\/p>\n
    \u9664\u4e86EXISTS\uff0c\u8fd8\u6709\u4e00\u4e2a\u7c7b\u4f3c\u7684\u64cd\u4f5c\u7b26NOT EXISTS\uff0c\u5b83\u7528\u4e8e\u5224\u65ad\u5b50\u67e5\u8be2\u662f\u5426\u6ca1\u6709\u8fd4\u56de\u4efb\u4f55\u6570\u636e\u3002\u53ef\u4ee5\u4f7f\u7528NOT EXISTS\u4e0eEXISTS\u7ed3\u5408\u4f7f\u7528\u6765\u5b9e\u73b0\u66f4\u590d\u6742\u7684\u67e5\u8be2\u903b\u8f91\u3002<\/p>\n
    \u7efc\u4e0a\u6240\u8ff0\uff0cMYSQL\u4e2d\u7684EXISTS\u64cd\u4f5c\u7b26\u662f\u4e00\u79cd\u975e\u5e38\u6709\u7528\u7684\u5de5\u5177\uff0c\u5b83\u80fd\u591f\u5e2e\u52a9\u6211\u4eec\u6839\u636e\u5b50\u67e5\u8be2\u7684\u7ed3\u679c\u8fdb\u884c\u6761\u4ef6\u7b5b\u9009\u3002\u4f7f\u7528EXISTS\u80fd\u591f\u7f16\u5199\u51fa\u66f4\u52a0\u7075\u6d3b\u3001\u5f3a\u5927\u7684\u67e5\u8be2\u8bed\u53e5\uff0c\u63d0\u9ad8\u67e5\u8be2\u6548\u7387\u548c\u51c6\u786e\u6027\u3002<\/p>\n
    \u4eca\u5929\u5173\u4e8e\u300a\u4f7f\u7528MYSQL\u4e2d\u7684EXISTS\u51fd\u6570\u300b\u7684\u5185\u5bb9\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\uff0c\u5982\u679c\u6709\u4ec0\u4e48\u7591\u95ee\u6216\u8005\u5efa\u8bae\uff0c\u53ef\u4ee5\u5728\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\u4e0b\u591a\u591a\u56de\u590d\u4ea4\u6d41\uff1b\u6587\u4e2d\u82e5\u6709\u4e0d\u6b63\u4e4b\u5904\uff0c\u4e5f\u5e0c\u671b\u56de\u590d\u7559\u8a00\u4ee5\u544a\u77e5\uff01<\/p>\n
    \n
    \n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"
    \u4f7f\u7528MYSQL\u4e2d\u7684EXISTS\u51fd...<\/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-199655","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199655","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=199655"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199655\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199655"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199655"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199655"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}