{"id":160039,"date":"2024-11-03T19:46:21","date_gmt":"2024-11-03T11:46:21","guid":{"rendered":"https:\/\/server.hk\/cnblog\/160039\/"},"modified":"2024-11-03T19:46:22","modified_gmt":"2024-11-03T11:46:22","slug":"mysql-%e6%95%99%e7%a8%8b-mysql-%e5%87%bd%e6%95%b8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/160039\/","title":{"rendered":"MYSQL \u6559\u7a0b MySQL \u51fd\u6578"},"content":{"rendered":"<h1 id=\"mysql-%e6%95%99%e7%a8%8b%ef%bc%9amysql-%e5%87%bd%e6%95%b8-QYEHgISstg\">MySQL \u6559\u7a0b\uff1aMySQL \u51fd\u6578<\/h1>\n<p>MySQL \u662f\u4e00\u7a2e\u6d41\u884c\u7684\u958b\u6e90\u95dc\u806f\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u5ee3\u6cdb\u61c9\u7528\u65bc\u5404\u7a2e\u7db2\u7ad9\u548c\u61c9\u7528\u7a0b\u5e8f\u4e2d\u3002\u4f5c\u70ba\u4e00\u500b\u5f37\u5927\u7684\u6578\u64da\u5eab\u7cfb\u7d71\uff0cMySQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u5167\u5efa\u51fd\u6578\uff0c\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u5e6b\u52a9\u7528\u6236\u9032\u884c\u6578\u64da\u8655\u7406\u3001\u67e5\u8a62\u548c\u5206\u6790\u3002\u672c\u6587\u5c07\u4ecb\u7d39\u4e00\u4e9b\u5e38\u7528\u7684 MySQL \u51fd\u6578\uff0c\u4e26\u63d0\u4f9b\u76f8\u61c9\u7684\u793a\u4f8b\uff0c\u4ee5\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u548c\u4f7f\u7528\u9019\u4e9b\u51fd\u6578\u3002<\/p>\n<h2 id=\"1-%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%87%bd%e6%95%b8-QYEHgISstg\">1. \u5b57\u7b26\u4e32\u51fd\u6578<\/h2>\n<p>MySQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u5b57\u7b26\u4e32\u8655\u7406\u51fd\u6578\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u7528\u7684\u5b57\u7b26\u4e32\u51fd\u6578\uff1a<\/p>\n<ul>\n<li><code>CONCAT()<\/code>\uff1a\u7528\u65bc\u5c07\u591a\u500b\u5b57\u7b26\u4e32\u9023\u63a5\u6210\u4e00\u500b\u5b57\u7b26\u4e32\u3002<\/li>\n<li><code>LENGTH()<\/code>\uff1a\u8fd4\u56de\u5b57\u7b26\u4e32\u7684\u9577\u5ea6\u3002<\/li>\n<li><code>UPPER()<\/code>\uff1a\u5c07\u5b57\u7b26\u4e32\u8f49\u63db\u70ba\u5927\u5beb\u3002<\/li>\n<li><code>LOWER()<\/code>\uff1a\u5c07\u5b57\u7b26\u4e32\u8f49\u63db\u70ba\u5c0f\u5beb\u3002<\/li>\n<\/ul>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a-QYEHgISstg\">\u793a\u4f8b\uff1a<\/h3>\n<pre><code>\nSELECT CONCAT('Hello', ' ', 'World') AS greeting; -- \u8f38\u51fa: Hello World\nSELECT LENGTH('Hello') AS length; -- \u8f38\u51fa: 5\nSELECT UPPER('hello') AS upper_case; -- \u8f38\u51fa: HELLO\nSELECT LOWER('HELLO') AS lower_case; -- \u8f38\u51fa: hello\n<\/code><\/pre>\n<h2 id=\"2-%e6%95%b8%e5%ad%b8%e5%87%bd%e6%95%b8-QYEHgISstg\">2. \u6578\u5b78\u51fd\u6578<\/h2>\n<p>MySQL \u4e5f\u63d0\u4f9b\u4e86\u591a\u7a2e\u6578\u5b78\u51fd\u6578\uff0c\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u7528\u65bc\u6578\u64da\u8a08\u7b97\u548c\u5206\u6790\uff1a<\/p>\n<ul>\n<li><code>ABS()<\/code>\uff1a\u8fd4\u56de\u6578\u5b57\u7684\u7d55\u5c0d\u503c\u3002<\/li>\n<li><code>ROUND()<\/code>\uff1a\u5c0d\u6578\u5b57\u9032\u884c\u56db\u6368\u4e94\u5165\u3002<\/li>\n<li><code>FLOOR()<\/code>\uff1a\u8fd4\u56de\u5c0f\u65bc\u6216\u7b49\u65bc\u6307\u5b9a\u6578\u5b57\u7684\u6700\u5927\u6574\u6578\u3002<\/li>\n<li><code>CEIL()<\/code>\uff1a\u8fd4\u56de\u5927\u65bc\u6216\u7b49\u65bc\u6307\u5b9a\u6578\u5b57\u7684\u6700\u5c0f\u6574\u6578\u3002<\/li>\n<\/ul>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a-QYEHgISstg\">\u793a\u4f8b\uff1a<\/h3>\n<pre><code>\nSELECT ABS(-10) AS absolute_value; -- \u8f38\u51fa: 10\nSELECT ROUND(10.567, 2) AS rounded_value; -- \u8f38\u51fa: 10.57\nSELECT FLOOR(10.9) AS floor_value; -- \u8f38\u51fa: 10\nSELECT CEIL(10.1) AS ceil_value; -- \u8f38\u51fa: 11\n<\/code><\/pre>\n<h2 id=\"3-%e6%97%a5%e6%9c%9f%e5%92%8c%e6%99%82%e9%96%93%e5%87%bd%e6%95%b8-QYEHgISstg\">3. \u65e5\u671f\u548c\u6642\u9593\u51fd\u6578<\/h2>\n<p>MySQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u65e5\u671f\u548c\u6642\u9593\u51fd\u6578\uff0c\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u7528\u65bc\u8655\u7406\u65e5\u671f\u548c\u6642\u9593\u6578\u64da\uff1a<\/p>\n<ul>\n<li><code>NOW()<\/code>\uff1a\u8fd4\u56de\u7576\u524d\u7684\u65e5\u671f\u548c\u6642\u9593\u3002<\/li>\n<li><code>CURDATE()<\/code>\uff1a\u8fd4\u56de\u7576\u524d\u7684\u65e5\u671f\u3002<\/li>\n<li><code>DATE_ADD()<\/code>\uff1a\u5411\u65e5\u671f\u6dfb\u52a0\u6307\u5b9a\u7684\u6642\u9593\u9593\u9694\u3002<\/li>\n<li><code>DATEDIFF()<\/code>\uff1a\u8a08\u7b97\u5169\u500b\u65e5\u671f\u4e4b\u9593\u7684\u5929\u6578\u3002<\/li>\n<\/ul>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a-QYEHgISstg\">\u793a\u4f8b\uff1a<\/h3>\n<pre><code>\nSELECT NOW() AS current_datetime; -- \u8f38\u51fa: \u7576\u524d\u65e5\u671f\u548c\u6642\u9593\nSELECT CURDATE() AS current_date; -- \u8f38\u51fa: \u7576\u524d\u65e5\u671f\nSELECT DATE_ADD('2023-01-01', INTERVAL 10 DAY) AS new_date; -- \u8f38\u51fa: 2023-01-11\nSELECT DATEDIFF('2023-01-11', '2023-01-01') AS days_difference; -- \u8f38\u51fa: 10\n<\/code><\/pre>\n<h2 id=\"4-%e8%81%9a%e5%90%88%e5%87%bd%e6%95%b8-QYEHgISstg\">4. \u805a\u5408\u51fd\u6578<\/h2>\n<p>\u805a\u5408\u51fd\u6578\u7528\u65bc\u5c0d\u6578\u64da\u9032\u884c\u8a08\u7b97\uff0c\u4e26\u8fd4\u56de\u55ae\u4e00\u7684\u503c\u3002\u5e38\u898b\u7684\u805a\u5408\u51fd\u6578\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><code>COUNT()<\/code>\uff1a\u8a08\u7b97\u884c\u6578\u3002<\/li>\n<li><code>SUM()<\/code>\uff1a\u8a08\u7b97\u6578\u5b57\u7684\u7e3d\u548c\u3002<\/li>\n<li><code>AVG()<\/code>\uff1a\u8a08\u7b97\u6578\u5b57\u7684\u5e73\u5747\u503c\u3002<\/li>\n<li><code>MAX()<\/code>\uff1a\u8fd4\u56de\u6700\u5927\u503c\u3002<\/li>\n<li><code>MIN()<\/code>\uff1a\u8fd4\u56de\u6700\u5c0f\u503c\u3002<\/li>\n<\/ul>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a-QYEHgISstg\">\u793a\u4f8b\uff1a<\/h3>\n<pre><code>\nSELECT COUNT(*) AS total_rows FROM users; -- \u8a08\u7b97\u7528\u6236\u8868\u4e2d\u7684\u884c\u6578\nSELECT SUM(salary) AS total_salary FROM employees; -- \u8a08\u7b97\u54e1\u5de5\u85aa\u8cc7\u7e3d\u548c\nSELECT AVG(age) AS average_age FROM users; -- \u8a08\u7b97\u7528\u6236\u7684\u5e73\u5747\u5e74\u9f61\nSELECT MAX(score) AS highest_score FROM tests; -- \u8fd4\u56de\u6700\u9ad8\u5206\nSELECT MIN(score) AS lowest_score FROM tests; -- \u8fd4\u56de\u6700\u4f4e\u5206\n<\/code><\/pre>\n<h2 id=\"%e7%b8%bd%e7%b5%90-QYEHgISstg\">\u7e3d\u7d50<\/h2>\n<p>MySQL \u51fd\u6578\u662f\u6578\u64da\u5eab\u64cd\u4f5c\u4e2d\u4e0d\u53ef\u6216\u7f3a\u7684\u4e00\u90e8\u5206\uff0c\u901a\u904e\u4f7f\u7528\u9019\u4e9b\u51fd\u6578\uff0c\u7528\u6236\u53ef\u4ee5\u66f4\u9ad8\u6548\u5730\u8655\u7406\u548c\u5206\u6790\u6578\u64da\u3002\u7121\u8ad6\u662f\u5b57\u7b26\u4e32\u8655\u7406\u3001\u6578\u5b78\u8a08\u7b97\u3001\u65e5\u671f\u6642\u9593\u64cd\u4f5c\u9084\u662f\u6578\u64da\u805a\u5408\uff0cMySQL \u90fd\u63d0\u4f9b\u4e86\u8c50\u5bcc\u7684\u51fd\u6578\u5eab\u4f86\u6eff\u8db3\u4e0d\u540c\u7684\u9700\u6c42\u3002\u5c0d\u65bc\u5e0c\u671b\u5728\u9999\u6e2f\u5c0b\u627e\u9ad8\u6548\u80fd\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\u7684\u7528\u6236\uff0c<a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u548c <a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a> \u63d0\u4f9b\u4e86\u7a69\u5b9a\u7684\u74b0\u5883\u4f86\u904b\u884c MySQL \u6578\u64da\u5eab\uff0c\u5e6b\u52a9\u7528\u6236\u66f4\u597d\u5730\u7ba1\u7406\u548c\u5206\u6790\u6578\u64da\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2 MySQL \u51fd\u6578\u7684\u5b8c\u6574\u6559\u7a0b\uff0c\u638c\u63e1\u6578\u64da\u5eab\u64cd\u4f5c\u3001\u67e5\u8a62\u512a\u5316\u53ca\u6578\u64da\u8655\u7406\u6280\u5de7\uff0c\u63d0\u5347\u60a8\u7684 MySQL \u4f7f\u7528\u80fd\u529b\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-160039","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160039","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=160039"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160039\/revisions"}],"predecessor-version":[{"id":160040,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160039\/revisions\/160040"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=160039"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=160039"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=160039"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}