{"id":344,"date":"2023-09-16T10:44:55","date_gmt":"2023-09-16T02:44:55","guid":{"rendered":""},"modified":"2023-09-16T15:50:11","modified_gmt":"2023-09-16T07:50:11","slug":"sql-%e6%88%aa%e5%8f%96%e5%ad%97%e7%ac%a6%e4%b8%b2%e5%b8%b8%e7%94%a8%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"https:\/\/mushiming.com\/344.html","title":{"rendered":"SQL\u2014\u2014\u622a\u53d6\u5b57\u7b26\u4e32\u5e38\u7528\u51fd\u6570"},"content":{"rendered":"<p><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"display: none;\"> \n <path stroke-linecap=\"round\" d=\"M5,0 0,2.5 5,5z\" id=\"raphael-marker-block\" style=\"-webkit-tap-highlight-color: rgba(0, 0, 0, 0);\"><\/path> \n<\/svg> <\/p>\n<div class=\"toc\">\n<h3>\u622a\u53d6\u5b57\u7b26\u4e32\u5e38\u7528\u51fd\u6570<\/h3>\n<ul>\n<li>1\u3001LEFT ( )<\/li>\n<li>2\u3001RIGHT ( )<\/li>\n<li>3\u3001SUBSTRING ( )<\/li>\n<\/ul>\n<\/div>\n<h1>1\u3001LEFT ( )<\/h1>\n<p><span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\"> \\quad \\quad <\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0em; vertical-align: 0em;\"><\/span><span class=\"mspace\" style=\"margin-right: 1em;\"><\/span><span class=\"mspace\" style=\"margin-right: 1em;\"><\/span><\/span><\/span><\/span><\/span>\u4ece\u5b57\u7b26\u4e32\u6700\u5de6\u8fb9\u5f00\u59cb\u622a\u53d6\u5373\u6b63\u5411\u622a\u53d6\uff0c\u8fd4\u56de\u4ece\u5b57\u7b26\u4e32\u5de6\u8fb9\u5f00\u59cb\u6307\u5b9a\u4e2a\u6570\u7684\u5b57\u7b26\u3002<\/p>\n<p>\u8bed\u6cd5\uff1a<\/p>\n<pre><code class=\"prism language-sql\"><span class=\"token keyword\">LEFT<\/span> <span class=\"token punctuation\">(<\/span> character_expression <span class=\"token punctuation\">,<\/span> integer_expression\uff09\n<\/code><\/pre>\n<p>\u53c2\u6570\uff1a<br \/> <code>character_expression<\/code>\uff1a\u6e90\u5b57\u7b26\u4e32 ,<br \/> <code>integer_expression<\/code> :\u8981\u622a\u53d6\u6700\u5de6\u8fb9\u7684\u5b57\u7b26\u6570<\/p>\n<p>eg:<\/p>\n<pre><code class=\"prism language-sql\"><span class=\"token keyword\">select<\/span> <span class=\"token keyword\">left<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">'SQL_Server'<\/span><span class=\"token punctuation\">,<\/span><span class=\"token number\">2<\/span> <span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>\n<\/code><\/pre>\n<p>\u8fd4\u56de\u7ed3\u679c\uff1aSQ<\/p>\n<h1>2\u3001RIGHT ( )<\/h1>\n<p><span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\"> \\quad \\quad <\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0em; vertical-align: 0em;\"><\/span><span class=\"mspace\" style=\"margin-right: 1em;\"><\/span><span class=\"mspace\" style=\"margin-right: 1em;\"><\/span><\/span><\/span><\/span><\/span>\u4ece\u5b57\u7b26\u4e32\u6700\u53f3\u8fb9\u5f00\u59cb\u622a\u53d6\u5373\u53cd\u5411\u622a\u53d6\uff0c\u8fd4\u56de\u5b57\u7b26\u4e32\u4e2d\u4ece\u53f3\u8fb9\u5f00\u59cb\u6307\u5b9a\u4e2a\u6570\u7684\u5b57\u7b26\u3002<\/p>\n<p>\u8bed\u6cd5\uff1a<\/p>\n<pre><code class=\"prism language-sql\"><span class=\"token keyword\">RIGHT<\/span> <span class=\"token punctuation\">(<\/span> character_expression <span class=\"token punctuation\">,<\/span> integer_expression <span class=\"token punctuation\">)<\/span>\n<\/code><\/pre>\n<p>\u53c2\u6570\uff1a<br \/> <code>character_expression<\/code>\uff1a\u6e90\u5b57\u7b26\u4e32 ,<br \/> <code>integer_expression<\/code> :\u8981\u622a\u53d6\u6700\u5de6\u8fb9\u7684\u5b57\u7b26\u6570<br \/> eg:<\/p>\n<pre><code class=\"prism language-sql\"><span class=\"token keyword\">select<\/span> <span class=\"token keyword\">RIGHT<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">'SQL_Server'<\/span><span class=\"token punctuation\">,<\/span><span class=\"token number\">2<\/span> <span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>\n<\/code><\/pre>\n<p>\u8fd4\u56de\u7ed3\u679c\uff1aer<\/p>\n<h1>3\u3001SUBSTRING ( )<\/h1>\n<p><span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\"> \\quad \\quad <\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0em; vertical-align: 0em;\"><\/span><span class=\"mspace\" style=\"margin-right: 1em;\"><\/span><span class=\"mspace\" style=\"margin-right: 1em;\"><\/span><\/span><\/span><\/span><\/span>\u8fd4\u56de\u5b57\u7b26\u3001binary\u3001text \u6216 image \u8868\u8fbe\u5f0f\u7684\u4e00\u90e8\u5206<br \/> \u8bed\u6cd5\uff1a<\/p>\n<pre><code class=\"prism language-sql\">SUBSTRING <span class=\"token punctuation\">(<\/span> character_expression <span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">start<\/span> <span class=\"token punctuation\">,<\/span> length <span class=\"token punctuation\">)<\/span>\n<\/code><\/pre>\n<p>\u53c2\u6570\uff1a<br \/> <code>character_expression<\/code>\uff1a\u6e90\u5b57\u7b26\u4e32 ,<br \/> <code>start<\/code>: \u622a\u53d6\u8d77\u59cb\u4f4d\u7f6e(\u542b\u8be5\u4f4d\u7f6e\u4e0a\u7684\u5b57\u7b26)<br \/> <code>length<\/code>: \u622a\u53d6\u957f\u5ea6<\/p>\n<p>eg:<\/p>\n<pre><code class=\"prism language-sql\"><span class=\"token keyword\">select<\/span> SUBSTRING<span class=\"token punctuation\">(<\/span><span class=\"token string\">'SQL_Server'<\/span><span class=\"token punctuation\">,<\/span><span class=\"token number\">5<\/span> <span class=\"token punctuation\">,<\/span><span class=\"token number\">6<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>\n<\/code><\/pre>\n<p>\u8fd4\u56de\u7ed3\u679c\uff1aServer<\/p>\n","protected":false},"excerpt":{"rendered":"\u622a\u53d6\u5b57\u7b26\u4e32\u5e38\u7528\u51fd\u65701\u3001LEFT()2\u3001RIGHT()3\u3001SUBSTRING()1\u3001LEFT()\\quad\\quad\u4ece\u5b57\u7b26\u4e32\u6700\u5de6\u8fb9\u5f00\u59cb\u622a\u53d6\u5373\u6b63\u5411\u622a\u53d6\uff0c\u8fd4\u56de\u4ece\u5b57\u7b26\u4e32...","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[82],"tags":[],"_links":{"self":[{"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/posts\/344"}],"collection":[{"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/comments?post=344"}],"version-history":[{"count":0,"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/posts\/344\/revisions"}],"wp:attachment":[{"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/media?parent=344"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/categories?post=344"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mushiming.com\/wp-json\/wp\/v2\/tags?post=344"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}