{"id":199656,"date":"2025-05-06T09:20:14","date_gmt":"2025-05-06T01:20:14","guid":{"rendered":"https:\/\/server.hk\/cnblog\/199656\/"},"modified":"2025-05-06T09:20:14","modified_gmt":"2025-05-06T01:20:14","slug":"%e5%a6%82%e4%bd%95%e5%9c%a8sql%e4%b8%ad%e4%bd%bf%e7%94%a8exists%e5%92%8cnot-exists%e6%93%8d%e4%bd%9c%e7%ac%a6","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/199656\/","title":{"rendered":"\u5982\u4f55\u5728SQL\u4e2d\u4f7f\u7528EXISTS\u548cNOT EXISTS\u64cd\u4f5c\u7b26"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>\u5982\u4f55\u5728SQL\u4e2d\u4f7f\u7528EXISTS\u548cNOT EXISTS\u64cd\u4f5c\u7b26<\/h1>\n<p>\u600e\u4e48\u5165\u95e8\u6570\u636e\u5e93\u7f16\u7a0b\uff1f\u9700\u8981\u5b66\u4e60\u54ea\u4e9b\u77e5\u8bc6\u70b9\uff1f\u8fd9\u662f\u65b0\u624b\u4eec\u521a\u63a5\u89e6\u7f16\u7a0b\u65f6\u5e38\u89c1\u7684\u95ee\u9898\uff1b\u4e0b\u9762\u4e3b\u673a\u5b9d\u8d1d\u5c31\u6765\u7ed9\u5927\u5bb6\u6574\u7406\u5206\u4eab\u4e00\u4e9b\u77e5\u8bc6\u70b9\uff0c\u5e0c\u671b\u80fd\u591f\u7ed9\u521d\u5b66\u8005\u4e00\u4e9b\u5e2e\u52a9\u3002\u672c\u7bc7\u6587\u7ae0\u5c31\u6765\u4ecb\u7ecd\u300a\u5982\u4f55\u5728SQL\u4e2d\u4f7f\u7528EXISTS\u548cNOT EXISTS\u64cd\u4f5c\u7b26\u300b\uff0c\u6d89\u53ca\u5230\uff0c\u6709\u9700\u8981\u7684\u53ef\u4ee5\u6536\u85cf\u4e00\u4e0b<\/p>\n<p>SQL\u4e2d\u7684exists\u548cnot exists\u7684\u7528\u6cd5\uff0c\u9700\u8981\u5177\u4f53\u7684\u4ee3\u7801\u793a\u4f8b<\/p>\n<p>\u5728SQL\u4e2d\uff0cexists\u548cnot exists\u662f\u4e00\u5bf9\u5e38\u7528\u7684\u8c13\u8bcd\uff08predicate\uff09\uff0c\u7528\u4e8e\u5224\u65ad\u4e00\u4e2a\u5b50\u67e5\u8be2\uff08subquery\uff09\u662f\u5426\u8fd4\u56de\u4e86\u7ed3\u679c\u96c6\u3002exists\u7528\u4e8e\u68c0\u67e5\u5b50\u67e5\u8be2\u662f\u5426\u81f3\u5c11\u8fd4\u56de\u4e00\u884c\u7ed3\u679c\uff0c\u800cnot exists\u7528\u4e8e\u68c0\u67e5\u5b50\u67e5\u8be2\u662f\u5426\u4e0d\u8fd4\u56de\u4efb\u4f55\u7ed3\u679c\u3002<\/p>\n<p>exists\u7684\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre>SELECT column1, column2, ...\nFROM table\nWHERE EXISTS (subquery);<\/pre>\n<p>not exists\u7684\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre>SELECT column1, column2, ...\nFROM table\nWHERE NOT EXISTS (subquery);<\/pre>\n<p>\u4e0b\u9762\u901a\u8fc7\u51e0\u4e2a\u5177\u4f53\u7684\u793a\u4f8b\u6765\u4ecb\u7ecdexists\u548cnot exists\u7684\u7528\u6cd5\u3002<\/p>\n<p>\u793a\u4f8b\u4e00\uff1a\u67e5\u627e\u5b58\u5728\u7279\u5b9a\u6761\u4ef6\u7684\u8bb0\u5f55<\/p>\n<p>\u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a\u540d\u4e3a&#8221;employees&#8221;\u7684\u8868\uff0c\u5305\u542b\u5458\u5de5\u7684\u4fe1\u606f\uff0c\u5176\u4e2d\u5305\u62ec&#8221;employee_id&#8221;\u3001&#8221;first_name&#8221;\u548c&#8221;last_name&#8221;\u7b49\u5217\u3002\u6211\u4eec\u60f3\u8981\u67e5\u627e\u6240\u6709\u5b58\u5728&#8221;manager&#8221;\u804c\u4f4d\u7684\u5458\u5de5\u4fe1\u606f\u3002<\/p>\n<pre>SELECT employee_id, first_name, last_name\nFROM employees\nWHERE EXISTS (SELECT 1\n              FROM employees\n              WHERE job_title = 'manager'\n                AND employees.employee_id = manager_id);<\/pre>\n<p>\u4e0a\u8ff0\u4ee3\u7801\u4e2d\u7684\u5b50\u67e5\u8be2\u662f\u4ece&#8221;employees&#8221;\u8868\u4e2d\u68c0\u7d22\u51fa\u5177\u6709&#8221;manager&#8221;\u804c\u4f4d\u7684\u8bb0\u5f55\u3002\u5916\u5c42\u7684\u4e3b\u67e5\u8be2\u4f7f\u7528exists\u8c13\u8bcd\u6765\u5224\u65ad\u8be5\u5b50\u67e5\u8be2\u662f\u5426\u81f3\u5c11\u8fd4\u56de\u4e86\u4e00\u884c\u7ed3\u679c\u3002<\/p>\n<p>\u793a\u4f8b\u4e8c\uff1a\u67e5\u627e\u4e0d\u5b58\u5728\u7279\u5b9a\u6761\u4ef6\u7684\u8bb0\u5f55<\/p>\n<p>\u5047\u8bbe\u73b0\u5728\u6211\u4eec\u5e0c\u671b\u67e5\u627e\u6ca1\u6709&#8221;manager&#8221;\u804c\u4f4d\u7684\u5458\u5de5\u4fe1\u606f\u3002<\/p>\n<pre>SELECT employee_id, first_name, last_name\nFROM employees\nWHERE NOT EXISTS (SELECT 1\n                  FROM employees\n                  WHERE job_title = 'manager'\n                    AND employees.employee_id = manager_id);<\/pre>\n<p>\u4e0a\u8ff0\u4ee3\u7801\u4e2d\u7684\u5b50\u67e5\u8be2\u540c\u6837\u662f\u4ece&#8221;employees&#8221;\u8868\u4e2d\u68c0\u7d22\u51fa\u5177\u6709&#8221;manager&#8221;\u804c\u4f4d\u7684\u8bb0\u5f55\u3002\u5916\u5c42\u7684\u4e3b\u67e5\u8be2\u4f7f\u7528not exists\u8c13\u8bcd\u6765\u5224\u65ad\u8be5\u5b50\u67e5\u8be2\u662f\u5426\u4e0d\u8fd4\u56de\u4efb\u4f55\u7ed3\u679c\u3002<\/p>\n<p>\u793a\u4f8b\u4e09\uff1a\u5b50\u67e5\u8be2\u7684\u5bf9\u6bd4<\/p>\n<p>\u4ee5exists\u548cnot exists\u4f5c\u4e3a\u8c13\u8bcd\u7684\u5b50\u67e5\u8be2\u4e5f\u53ef\u4ee5\u4f7f\u7528\u5176\u4ed6\u6761\u4ef6\u8fdb\u884c\u7b5b\u9009\u3002<\/p>\n<p>\u5047\u8bbe\u6211\u4eec\u60f3\u8981\u67e5\u627e\u5de5\u8d44\u6700\u9ad8\u7684\u5458\u5de5\u4fe1\u606f\u3002<\/p>\n<pre>SELECT employee_id, first_name, last_name\nFROM employees e1\nWHERE NOT EXISTS (SELECT 1\n                  FROM employees e2\n                  WHERE e2.salary &gt; e1.salary);<\/pre>\n<p>\u5728\u4e0a\u8ff0\u4ee3\u7801\u4e2d\uff0c\u5b50\u67e5\u8be2\u68c0\u7d22\u51fa\u5de5\u8d44\u5927\u4e8e\u5f53\u524d\u5458\u5de5\u7684\u8bb0\u5f55\uff0c\u5e76\u901a\u8fc7not exists\u8c13\u8bcd\u5224\u65ad\u662f\u5426\u4e0d\u5b58\u5728\u6ee1\u8db3\u6761\u4ef6\u7684\u8bb0\u5f55\u3002<\/p>\n<p>\u603b\u7ed3\uff1a<\/p>\n<p>exists\u548cnot exists\u662fSQL\u4e2d\u5e38\u7528\u7684\u8c13\u8bcd\uff0c\u7528\u4e8e\u68c0\u67e5\u5b50\u67e5\u8be2\u662f\u5426\u8fd4\u56de\u7ed3\u679c\u96c6\u3002exists\u7528\u4e8e\u5224\u65ad\u81f3\u5c11\u5b58\u5728\u4e00\u884c\u7ed3\u679c\uff0cnot exists\u7528\u4e8e\u5224\u65ad\u4e0d\u5b58\u5728\u4efb\u4f55\u7ed3\u679c\u3002\u901a\u8fc7\u4f7f\u7528exists\u548cnot exists\uff0c\u6211\u4eec\u53ef\u4ee5\u7f16\u5199\u51fa\u66f4\u52a0\u7075\u6d3b\u7684\u67e5\u8be2\u8bed\u53e5\uff0c\u4ee5\u6ee1\u8db3\u4e0d\u540c\u7684\u4e1a\u52a1\u9700\u6c42\u3002<\/p>\n<p>\u597d\u4e86\uff0c\u672c\u6587\u5230\u6b64\u7ed3\u675f\uff0c\u5e26\u5927\u5bb6\u4e86\u89e3\u4e86\u300a\u5982\u4f55\u5728SQL\u4e2d\u4f7f\u7528EXISTS\u548cNOT EXISTS\u64cd\u4f5c\u7b26\u300b\uff0c\u5e0c\u671b\u672c\u6587\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\uff01\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff0c\u7ed9\u5927\u5bb6\u5206\u4eab\u66f4\u591a\u6570\u636e\u5e93\u77e5\u8bc6\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>\u5982\u4f55\u5728SQL\u4e2d\u4f7f\u7528EXISTS\u548c&#46;&#46;&#46;<\/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-199656","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199656","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=199656"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/199656\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=199656"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=199656"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=199656"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}