{"id":77844,"date":"2024-10-16T11:13:16","date_gmt":"2024-10-16T03:13:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/77844\/"},"modified":"2024-10-16T11:13:16","modified_gmt":"2024-10-16T03:13:16","slug":"mysql%e6%8c%87%e4%bb%a4-cast%ef%bc%88%e9%a1%9e%e5%9e%8b%e8%bd%89%e6%8f%9b%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/77844\/","title":{"rendered":"MySQL\u6307\u4ee4: CAST()\uff08\u985e\u578b\u8f49\u63db\uff09"},"content":{"rendered":"<h1 id=\"mysql%e6%8c%87%e4%bb%a4-cast%ef%bc%88%e9%a1%9e%e5%9e%8b%e8%bd%89%e6%8f%9b%ef%bc%89-MplUIhywTz\">MySQL\u6307\u4ee4: CAST()\uff08\u985e\u578b\u8f49\u63db\uff09<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u6578\u64da\u985e\u578b\u7684\u8f49\u63db\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002MySQL\u63d0\u4f9b\u4e86\u591a\u7a2e\u65b9\u6cd5\u4f86\u9032\u884c\u6578\u64da\u985e\u578b\u7684\u8f49\u63db\uff0c\u5176\u4e2d\u6700\u5e38\u7528\u7684\u5c31\u662fCAST()\u51fd\u6578\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eCAST()\u51fd\u6578\u7684\u7528\u6cd5\u3001\u8a9e\u6cd5\u53ca\u5176\u61c9\u7528\u5834\u666f\u3002<\/p>\n<h2 id=\"cast%e5%87%bd%e6%95%b8%e6%a6%82%e8%bf%b0-MplUIhywTz\">CAST()\u51fd\u6578\u6982\u8ff0<\/h2>\n<p>CAST()\u51fd\u6578\u7528\u65bc\u5c07\u4e00\u500b\u6578\u64da\u985e\u578b\u8f49\u63db\u70ba\u53e6\u4e00\u500b\u6578\u64da\u985e\u578b\u3002\u9019\u5728\u8655\u7406\u4e0d\u540c\u985e\u578b\u7684\u6578\u64da\u6642\u975e\u5e38\u6709\u7528\uff0c\u4f8b\u5982\u5728\u9032\u884c\u6578\u5b78\u904b\u7b97\u6216\u5b57\u7b26\u4e32\u64cd\u4f5c\u6642\uff0c\u53ef\u80fd\u9700\u8981\u5c07\u6578\u5b57\u8f49\u63db\u70ba\u5b57\u7b26\u4e32\uff0c\u6216\u5c07\u5b57\u7b26\u4e32\u8f49\u63db\u70ba\u6578\u5b57\u3002<\/p>\n<h2 id=\"cast%e7%9a%84%e8%aa%9e%e6%b3%95-MplUIhywTz\">CAST()\u7684\u8a9e\u6cd5<\/h2>\n<pre><code>CAST(expression AS target_data_type)<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>expression<\/code>\u662f\u8981\u8f49\u63db\u7684\u6578\u64da\uff0c<code>target_data_type<\/code>\u662f\u76ee\u6a19\u6578\u64da\u985e\u578b\u3002MySQL\u652f\u6301\u591a\u7a2e\u6578\u64da\u985e\u578b\uff0c\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><code>CHAR<\/code><\/li>\n<li><code>VARCHAR<\/code><\/li>\n<li><code>BINARY<\/code><\/li>\n<li><code>DECIMAL<\/code><\/li>\n<li><code>DATE<\/code><\/li>\n<li><code>DATETIME<\/code><\/li>\n<li><code>TIME<\/code><\/li>\n<li><code>SIGNED<\/code><\/li>\n<li><code>UNSIGNED<\/code><\/li>\n<\/ul>\n<h2 id=\"cast%e7%9a%84%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-MplUIhywTz\">CAST()\u7684\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e9b\u4f7f\u7528CAST()\u51fd\u6578\u7684\u7bc4\u4f8b\uff1a<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b1-%e5%b0%87%e6%95%b4%e6%95%b8%e8%bd%89%e6%8f%9b%e7%82%ba%e5%ad%97%e7%ac%a6%e4%b8%b2-MplUIhywTz\">\u7bc4\u4f8b1: \u5c07\u6574\u6578\u8f49\u63db\u70ba\u5b57\u7b26\u4e32<\/h3>\n<pre><code>SELECT CAST(123 AS CHAR);<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u6574\u6578123\u8f49\u63db\u70ba\u5b57\u7b26\u4e32&#8217;123&#8217;\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b2-%e5%b0%87%e5%ad%97%e7%ac%a6%e4%b8%b2%e8%bd%89%e6%8f%9b%e7%82%ba%e6%95%b4%e6%95%b8-MplUIhywTz\">\u7bc4\u4f8b2: \u5c07\u5b57\u7b26\u4e32\u8f49\u63db\u70ba\u6574\u6578<\/h3>\n<pre><code>SELECT CAST('456' AS UNSIGNED);<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u5b57\u7b26\u4e32&#8217;456&#8217;\u8f49\u63db\u70ba\u6574\u6578456\u3002<\/p>\n<h3 id=\"%e7%af%84%e4%be%8b3-%e5%b0%87%e6%97%a5%e6%9c%9f%e8%bd%89%e6%8f%9b%e7%82%ba%e5%ad%97%e7%ac%a6%e4%b8%b2-MplUIhywTz\">\u7bc4\u4f8b3: \u5c07\u65e5\u671f\u8f49\u63db\u70ba\u5b57\u7b26\u4e32<\/h3>\n<pre><code>SELECT CAST(NOW() AS CHAR);<\/code><\/pre>\n<p>\u9019\u689d\u8a9e\u53e5\u5c07\u7576\u524d\u7684\u65e5\u671f\u548c\u6642\u9593\u8f49\u63db\u70ba\u5b57\u7b26\u4e32\u683c\u5f0f\u3002<\/p>\n<h2 id=\"cast%e7%9a%84%e6%87%89%e7%94%a8%e5%a0%b4%e6%99%af-MplUIhywTz\">CAST()\u7684\u61c9\u7528\u5834\u666f<\/h2>\n<p>CAST()\u51fd\u6578\u5728\u591a\u7a2e\u60c5\u6cc1\u4e0b\u90fd\u975e\u5e38\u6709\u7528\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u61c9\u7528\u5834\u666f\uff1a<\/p>\n<ul>\n<li><strong>\u6578\u64da\u6bd4\u8f03\uff1a<\/strong>\u5728\u9032\u884c\u6578\u64da\u6bd4\u8f03\u6642\uff0c\u78ba\u4fdd\u6578\u64da\u985e\u578b\u4e00\u81f4\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002\u4f7f\u7528CAST()\u53ef\u4ee5\u907f\u514d\u56e0\u6578\u64da\u985e\u578b\u4e0d\u5339\u914d\u800c\u5c0e\u81f4\u7684\u932f\u8aa4\u3002<\/li>\n<li><strong>\u6578\u64da\u683c\u5f0f\u5316\uff1a<\/strong>\u5728\u751f\u6210\u5831\u544a\u6216\u986f\u793a\u6578\u64da\u6642\uff0c\u53ef\u80fd\u9700\u8981\u5c07\u6578\u64da\u683c\u5f0f\u5316\u70ba\u7279\u5b9a\u7684\u985e\u578b\uff0c\u4f8b\u5982\u5c07\u6578\u5b57\u683c\u5f0f\u5316\u70ba\u8ca8\u5e63\u3002<\/li>\n<li><strong>\u6578\u64da\u63d2\u5165\uff1a<\/strong>\u5728\u63d2\u5165\u6578\u64da\u6642\uff0c\u78ba\u4fdd\u6578\u64da\u985e\u578b\u6b63\u78ba\u53ef\u4ee5\u907f\u514d\u63d2\u5165\u5931\u6557\u3002<\/li>\n<\/ul>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-MplUIhywTz\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u5728\u4f7f\u7528CAST()\u51fd\u6578\u6642\uff0c\u6709\u5e7e\u9ede\u9700\u8981\u6ce8\u610f\uff1a<\/p>\n<ul>\n<li>\u8f49\u63db\u53ef\u80fd\u6703\u5c0e\u81f4\u6578\u64da\u4e1f\u5931\uff0c\u4f8b\u5982\u5c07\u6d6e\u9ede\u6578\u8f49\u63db\u70ba\u6574\u6578\u6642\uff0c\u5c0f\u6578\u90e8\u5206\u5c07\u88ab\u622a\u65b7\u3002<\/li>\n<li>\u67d0\u4e9b\u8f49\u63db\u53ef\u80fd\u6703\u5931\u6557\uff0c\u4f8b\u5982\u5c07\u7121\u6cd5\u8f49\u63db\u7684\u5b57\u7b26\u4e32\u8f49\u63db\u70ba\u6578\u5b57\u6642\uff0c\u5c07\u8fd4\u56deNULL\u3002<\/li>\n<li>\u5728\u9032\u884c\u5927\u91cf\u6578\u64da\u8f49\u63db\u6642\uff0c\u53ef\u80fd\u6703\u5f71\u97ff\u6027\u80fd\uff0c\u56e0\u6b64\u61c9\u8b39\u614e\u4f7f\u7528\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-MplUIhywTz\">\u7e3d\u7d50<\/h2>\n<p>CAST()\u51fd\u6578\u662fMySQL\u4e2d\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u5728\u4e0d\u540c\u6578\u64da\u985e\u578b\u4e4b\u9593\u9032\u884c\u8f49\u63db\u3002\u7121\u8ad6\u662f\u5728\u6578\u64da\u6bd4\u8f03\u3001\u683c\u5f0f\u5316\u9084\u662f\u63d2\u5165\u904e\u7a0b\u4e2d\uff0c\u6b63\u78ba\u4f7f\u7528CAST()\u90fd\u80fd\u63d0\u9ad8\u6578\u64da\u8655\u7406\u7684\u9748\u6d3b\u6027\u548c\u6e96\u78ba\u6027\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u7ba1\u7406\u7684\u7528\u6236\uff0c\u9078\u64c7\u5408\u9069\u7684<code><a href=\"https:\/\/server.hk\">VPS<\/a><\/code>\u89e3\u6c7a\u65b9\u6848\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u6574\u9ad4\u6027\u80fd\u548c\u7a69\u5b9a\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u4e2d\u7684CAST()\u6307\u4ee4\uff0c\u8f15\u9b06\u9032\u884c\u6578\u64da\u985e\u578b\u8f49\u63db\uff0c\u63d0\u5347\u67e5\u8a62\u9748\u6d3b\u6027\u8207\u6578\u64da\u8655\u7406\u6548\u7387\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-77844","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77844","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=77844"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77844\/revisions"}],"predecessor-version":[{"id":77845,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/77844\/revisions\/77845"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=77844"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=77844"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=77844"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}