{"id":143989,"date":"2024-11-01T02:56:17","date_gmt":"2024-10-31T18:56:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/143989\/"},"modified":"2024-11-01T02:56:18","modified_gmt":"2024-10-31T18:56:18","slug":"sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%aa%a2%e7%b4%a2%e6%96%b9%e6%b3%95%e8%a9%b3%e8%a7%a3-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%aa%a2%e7%b4%a2%e6%96%b9%e5%bc%8f-sql","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/143989\/","title":{"rendered":"SQL \u6578\u64da\u5eab\u6aa2\u7d22\u65b9\u6cd5\u8a73\u89e3 (\u6578\u64da\u5eab\u6aa2\u7d22\u65b9\u5f0f sql)"},"content":{"rendered":"<h1 id=\"sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%aa%a2%e7%b4%a2%e6%96%b9%e6%b3%95%e8%a9%b3%e8%a7%a3-%e6%95%b8%e6%93%9a%e5%ba%ab%e6%aa%a2%e7%b4%a2%e6%96%b9%e5%bc%8f-sql-xlwzrnyiEl\">SQL \u6578\u64da\u5eab\u6aa2\u7d22\u65b9\u6cd5\u8a73\u89e3 (\u6578\u64da\u5eab\u6aa2\u7d22\u65b9\u5f0f SQL)<\/h1>\n<p>\u5728\u7576\u4eca\u6578\u64da\u9a45\u52d5\u7684\u4e16\u754c\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u6210\u70ba\u4e86\u6578\u64da\u5eab\u7ba1\u7406\u548c\u6aa2\u7d22\u7684\u6838\u5fc3\u5de5\u5177\u3002\u7121\u8ad6\u662f\u4f01\u696d\u7d1a\u61c9\u7528\u9084\u662f\u500b\u4eba\u9805\u76ee\uff0c\u638c\u63e1 SQL \u7684\u6aa2\u7d22\u65b9\u6cd5\u5c0d\u65bc\u6709\u6548\u7ba1\u7406\u548c\u5206\u6790\u6578\u64da\u81f3\u95dc\u91cd\u8981\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e SQL \u6578\u64da\u5eab\u7684\u6aa2\u7d22\u65b9\u6cd5\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u5982\u4f55\u4f7f\u7528 SQL \u9032\u884c\u6578\u64da\u6aa2\u7d22\u3002<\/p>\n<h2 id=\"%e5%9f%ba%e6%9c%ac%e7%9a%84-sql-%e6%9f%a5%e8%a9%a2%e8%aa%9e%e5%8f%a5-xlwzrnyiEl\">\u57fa\u672c\u7684 SQL \u67e5\u8a62\u8a9e\u53e5<\/h2>\n<p>SQL \u7684\u57fa\u672c\u67e5\u8a62\u8a9e\u53e5\u662f <code>SELECT<\/code>\uff0c\u5b83\u7528\u65bc\u5f9e\u6578\u64da\u5eab\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT column1, column2, ...\nFROM table_name\nWHERE condition;<\/code><\/pre>\n<p>\u4f8b\u5982\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>employees<\/code> \u7684\u8868\uff0c\u60f3\u8981\u6aa2\u7d22\u6240\u6709\u54e1\u5de5\u7684\u59d3\u540d\u548c\u8077\u4f4d\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u67e5\u8a62\uff1a<\/p>\n<pre><code>SELECT name, position\nFROM employees;<\/code><\/pre>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e6%a2%9d%e4%bb%b6%e9%81%8e%e6%bf%be%e6%95%b8%e6%93%9a-xlwzrnyiEl\">\u4f7f\u7528\u689d\u4ef6\u904e\u6ffe\u6578\u64da<\/h2>\n<p>\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0c\u6211\u5011\u7d93\u5e38\u9700\u8981\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u904e\u6ffe\u6578\u64da\u3002\u9019\u53ef\u4ee5\u901a\u904e <code>WHERE<\/code> \u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u53ea\u60f3\u6aa2\u7d22\u8077\u4f4d\u70ba\u201c\u7d93\u7406\u201d\u7684\u54e1\u5de5\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT name, position\nFROM employees\nWHERE position = '\u7d93\u7406';<\/code><\/pre>\n<h2 id=\"%e6%8e%92%e5%ba%8f%e6%aa%a2%e7%b4%a2%e7%b5%90%e6%9e%9c-xlwzrnyiEl\">\u6392\u5e8f\u6aa2\u7d22\u7d50\u679c<\/h2>\n<p>\u6709\u6642\u5019\uff0c\u6211\u5011\u9700\u8981\u5c0d\u6aa2\u7d22\u5230\u7684\u6578\u64da\u9032\u884c\u6392\u5e8f\u3002\u9019\u53ef\u4ee5\u901a\u904e <code>ORDER BY<\/code> \u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4ee5\u4e0b\u793a\u4f8b\u5c55\u793a\u4e86\u5982\u4f55\u6309\u59d3\u540d\u7684\u5b57\u6bcd\u9806\u5e8f\u6392\u5e8f\uff1a<\/p>\n<pre><code>SELECT name, position\nFROM employees\nORDER BY name ASC;<\/code><\/pre>\n<p>\u5982\u679c\u9700\u8981\u6309\u964d\u5e8f\u6392\u5e8f\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>DESC<\/code>\uff1a<\/p>\n<pre><code>SELECT name, position\nFROM employees\nORDER BY name DESC;<\/code><\/pre>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e8%81%9a%e5%90%88%e5%87%bd%e6%95%b8-xlwzrnyiEl\">\u4f7f\u7528\u805a\u5408\u51fd\u6578<\/h2>\n<p>SQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u805a\u5408\u51fd\u6578\uff0c\u5982 <code>COUNT<\/code>\u3001<code>SUM<\/code>\u3001<code>AVG<\/code>\u3001<code>MAX<\/code> \u548c <code>MIN<\/code>\uff0c\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u5e6b\u52a9\u6211\u5011\u9032\u884c\u6578\u64da\u5206\u6790\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u8a08\u7b97\u54e1\u5de5\u7684\u7e3d\u6578\uff0c\u53ef\u4ee5\u4f7f\u7528\uff1a<\/p>\n<pre><code>SELECT COUNT(*)\nFROM employees;<\/code><\/pre>\n<h2 id=\"%e5%88%86%e7%b5%84%e6%95%b8%e6%93%9a-xlwzrnyiEl\">\u5206\u7d44\u6578\u64da<\/h2>\n<p>\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6211\u5011\u9700\u8981\u5c0d\u6578\u64da\u9032\u884c\u5206\u7d44\u4ee5\u9032\u884c\u66f4\u6df1\u5165\u7684\u5206\u6790\u3002\u9019\u53ef\u4ee5\u901a\u904e <code>GROUP BY<\/code> \u5b50\u53e5\u4f86\u5be6\u73fe\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u6309\u8077\u4f4d\u7d71\u8a08\u6bcf\u500b\u8077\u4f4d\u7684\u54e1\u5de5\u6578\u91cf\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n<pre><code>SELECT position, COUNT(*)\nFROM employees\nGROUP BY position;<\/code><\/pre>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e8%81%af%e6%8e%a5%e6%9f%a5%e8%a9%a2-xlwzrnyiEl\">\u4f7f\u7528\u806f\u63a5\u67e5\u8a62<\/h2>\n<p>\u5728\u591a\u500b\u8868\u4e4b\u9593\u9032\u884c\u6578\u64da\u6aa2\u7d22\u6642\uff0c\u806f\u63a5\u67e5\u8a62\u662f\u975e\u5e38\u6709\u7528\u7684\u3002SQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u806f\u63a5\u65b9\u5f0f\uff0c\u5982\u5167\u806f\u63a5\uff08INNER JOIN\uff09\u3001\u5916\u806f\u63a5\uff08LEFT JOIN\u3001RIGHT JOIN\uff09\u7b49\u3002\u4ee5\u4e0b\u662f\u5167\u806f\u63a5\u7684\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT employees.name, departments.department_name\nFROM employees\nINNER JOIN departments ON employees.department_id = departments.id;<\/code><\/pre>\n<h2 id=\"%e5%b0%8f%e7%b5%90-xlwzrnyiEl\">\u5c0f\u7d50<\/h2>\n<p>SQL \u6578\u64da\u5eab\u6aa2\u7d22\u65b9\u6cd5\u662f\u6578\u64da\u7ba1\u7406\u548c\u5206\u6790\u7684\u57fa\u790e\u3002\u901a\u904e\u638c\u63e1\u57fa\u672c\u7684\u67e5\u8a62\u8a9e\u53e5\u3001\u689d\u4ef6\u904e\u6ffe\u3001\u6392\u5e8f\u3001\u805a\u5408\u51fd\u6578\u3001\u5206\u7d44\u548c\u806f\u63a5\u67e5\u8a62\uff0c\u4f7f\u7528\u8005\u53ef\u4ee5\u6709\u6548\u5730\u5f9e\u6578\u64da\u5eab\u4e2d\u63d0\u53d6\u6240\u9700\u7684\u4fe1\u606f\u3002\u96a8\u8457\u6578\u64da\u91cf\u7684\u589e\u9577\uff0c\u9019\u4e9b\u6280\u80fd\u5c07\u8b8a\u5f97\u8d8a\u4f86\u8d8a\u91cd\u8981\u3002<\/p>\n<p>\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u4f86\u652f\u6301\u60a8\u7684\u6578\u64da\u5eab\u61c9\u7528\uff0cServer.HK \u63d0\u4f9b\u4e86\u591a\u7a2e\u9078\u64c7\uff0c\u5e6b\u52a9\u60a8\u8f15\u9b06\u7ba1\u7406\u548c\u64f4\u5c55\u60a8\u7684\u6578\u64da\u5eab\u9700\u6c42\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6df1\u5165\u63a2\u8a0eSQL\u6578\u64da\u5eab\u6aa2\u7d22\u65b9\u6cd5\uff0c\u4e86\u89e3\u5404\u7a2e\u6aa2\u7d22\u65b9\u5f0f\u53ca\u5176\u61c9\u7528\uff0c\u63d0\u5347\u6578\u64da\u67e5\u8a62\u6548\u7387\u8207\u6e96\u78ba\u6027\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-143989","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143989","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"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=143989"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143989\/revisions"}],"predecessor-version":[{"id":143990,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143989\/revisions\/143990"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=143989"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=143989"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=143989"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}