{"id":5194,"date":"2024-11-14T12:23:30","date_gmt":"2024-11-14T04:23:30","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5194\/"},"modified":"2024-11-14T12:23:30","modified_gmt":"2024-11-14T04:23:30","slug":"sql%e4%b8%adsubstring%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5194\/","title":{"rendered":"sql\u4e2dsubstring\u7528\u6cd5"},"content":{"rendered":"

\n substring \u51fd\u6570\u7528\u4e8e\u4ece\u5b57\u7b26\u4e32\u4e2d\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\uff0c\u8bed\u6cd5\u4e3a substring(string, start, length)\u3002\u53c2\u6570\u5305\u62ec string (\u8981\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u7684\u5b57\u7b26\u4e32)\uff0cstart (\u5b50\u5b57\u7b26\u4e32\u7684\u8d77\u59cb\u4f4d\u7f6e) \u548c length (\u8981\u63d0\u53d6\u7684\u5b57\u7b26\u6570)\u3002\u5176\u4ed6\u7528\u6cd5\u5305\u62ec\u8d1f\u6570\u8d77\u59cb\u4f4d\u7f6e\u3001\u7701\u7565\u957f\u5ea6\u53c2\u6570\u548c\u5904\u7406 null \u503c\u3002\n<\/p><\/blockquote>\n

\"sql\u4e2dsubstring\u7528\u6cd5\u63d2\u56fe\"<\/p>\n

SQL \u4e2d SUBSTRING \u7528\u6cd5<\/strong><\/p>\n

SUBSTRING \u51fd\u6570\u7528\u4e8e\u4ece\u5b57\u7b26\u4e32\u4e2d\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u3002\u5176\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n

SUBSTRING(string, start, length)<\/pre>\n
  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
\u53c2\u6570\u8bf4\u660e\uff1a<\/strong><\/p>\n
    \n
  •  string\uff1a<\/strong>\u8981\u4ece\u4e2d\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u7684\u5b57\u7b26\u4e32\u3002<\/li>\n
  •  start\uff1a<\/strong>\u5b50\u5b57\u7b26\u4e32\u7684\u8d77\u59cb\u4f4d\u7f6e\uff0c\u4ece 1 \u5f00\u59cb\u3002<\/li>\n
  •  length\uff1a<\/strong>\u8981\u63d0\u53d6\u7684\u5b57\u7b26\u6570\u3002<\/li>\n<\/ul>\n
    \u793a\u4f8b\uff1a<\/strong><\/p>\n
    SELECT SUBSTRING('Hello World', 3, 5);  -- \u8f93\u51fa\uff1allo W<\/pre>\n
      \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
    \u5176\u4ed6\u7528\u6cd5\uff1a<\/strong><\/p>\n
    \u9664\u4e86\u6307\u5b9a\u660e\u786e\u7684\u8d77\u59cb\u4f4d\u7f6e\u548c\u957f\u5ea6\u5916\uff0cSUBSTRING \u51fd\u6570\u8fd8\u652f\u6301\u4ee5\u4e0b\u7528\u6cd5\uff1a<\/p>\n
      \n
    •  \u8d1f\u6570\u8d77\u59cb\u4f4d\u7f6e\uff1a<\/strong>\u4ece\u5b57\u7b26\u4e32\u5c3e\u90e8\u5f00\u59cb\u8ba1\u6570\u3002\u4f8b\u5982\uff1a<\/li>\n<\/ul>\n
      SELECT SUBSTRING('Hello World', -3, 2);  -- \u8f93\u51fa\uff1ald<\/pre>\n
        \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
        \n
      •  \u7701\u7565\u957f\u5ea6\u53c2\u6570\uff1a<\/strong>\u4ece\u8d77\u59cb\u4f4d\u7f6e\u5230\u5b57\u7b26\u4e32\u672b\u5c3e\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u3002\u4f8b\u5982\uff1a<\/li>\n<\/ul>\n
        SELECT SUBSTRING('Hello World', 3);  -- \u8f93\u51fa\uff1allo World<\/pre>\n
          \u767b\u5f55\u540e\u590d\u5236   <\/p>\n
          \n
        •  NULL \u503c\uff1a<\/strong>\u5f53\u4efb\u4f55\u53c2\u6570\u4e3a NULL \u65f6\uff0c\u7ed3\u679c\u4e3a NULL\u3002<\/li>\n<\/ul>\n
          \u6ce8\u610f\u4e8b\u9879\uff1a<\/strong><\/p>\n
            \n
          • \u5982\u679c start<\/strong> \u6216 length<\/strong> \u5c0f\u4e8e 1\uff0c\u5219\u8fd4\u56de\u7a7a\u5b57\u7b26\u4e32\u3002<\/li>\n
          • \u5982\u679c start<\/strong> \u8d85\u8fc7\u5b57\u7b26\u4e32\u957f\u5ea6\uff0c\u5219\u8fd4\u56de\u7a7a\u5b57\u7b26\u4e32\u3002<\/li>\n
          • \u5982\u679c length<\/strong> \u8d85\u8fc7\u5b57\u7b26\u4e32\u7684\u5269\u4f59\u957f\u5ea6\uff0c\u5219\u53ea\u8fd4\u56de\u5269\u4f59\u7684\u5b57\u7b26\u3002<\/li>\n<\/ul>\n
            \u4ee5\u4e0a\u5c31\u662fsql\u4e2dsubstring\u7528\u6cd5\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
            substring \u51fd\u6570\u7528\u4e8e\u4ece\u5b57\u7b26\u4e32\u4e2d\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\uff0c\u8bed\u6cd5\u4e3a substring(string, start, length)\u3002\u53c2\u6570\u5305\u62ec string (\u8981\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u7684\u5b57\u7b26\u4e32)\uff0cstart (\u5b50\u5b57\u7b26\u4e32\u7684\u8d77\u59cb\u4f4d\u7f6e) \u548c length (\u8981\u63d0\u53d6\u7684\u5b57\u7b26\u6570)\u3002\u5176\u4ed6\u7528\u6cd5\u5305\u62ec\u8d1f\u6570\u8d77\u59cb\u4f4d\u7f6e\u3001\u7701\u7565\u957f\u5ea6\u53c2\u6570\u548c\u5904\u7406 null \u503c\u3002 SQL \u4e2d SUBSTRING \u7528\u6cd5 SUBSTRING \u51fd\u6570\u7528\u4e8e\u4ece\u5b57\u7b26\u4e32\u4e2d\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u3002\u5176\u8bed\u6cd5\u5982\u4e0b\uff1a SUBSTRING(string, start, length) \u767b\u5f55\u540e\u590d\u5236 \u53c2\u6570\u8bf4\u660e\uff1a string\uff1a\u8981\u4ece\u4e2d\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u7684\u5b57\u7b26\u4e32\u3002 start\uff1a\u5b50\u5b57\u7b26\u4e32\u7684\u8d77\u59cb\u4f4d\u7f6e\uff0c\u4ece 1 \u5f00\u59cb\u3002 length\uff1a\u8981\u63d0\u53d6\u7684\u5b57\u7b26\u6570\u3002 \u793a\u4f8b\uff1a SELECT SUBSTRING(‘Hello World’, 3, 5); — \u8f93\u51fa\uff1allo W \u767b\u5f55\u540e\u590d\u5236 \u5176\u4ed6\u7528\u6cd5\uff1a \u9664\u4e86\u6307\u5b9a\u660e\u786e\u7684\u8d77\u59cb\u4f4d\u7f6e\u548c\u957f\u5ea6\u5916\uff0cSUBSTRING \u51fd\u6570\u8fd8\u652f\u6301\u4ee5\u4e0b\u7528\u6cd5\uff1a \u8d1f\u6570\u8d77\u59cb\u4f4d\u7f6e\uff1a\u4ece\u5b57\u7b26\u4e32\u5c3e\u90e8\u5f00\u59cb\u8ba1\u6570\u3002\u4f8b\u5982\uff1a SELECT SUBSTRING(‘Hello World’, -3, 2); — \u8f93\u51fa\uff1ald \u767b\u5f55\u540e\u590d\u5236 \u7701\u7565\u957f\u5ea6\u53c2\u6570\uff1a\u4ece\u8d77\u59cb\u4f4d\u7f6e\u5230\u5b57\u7b26\u4e32\u672b\u5c3e\u63d0\u53d6\u5b50\u5b57\u7b26\u4e32\u3002\u4f8b\u5982\uff1a SELECT SUBSTRING(‘Hello World’, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-5194","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5194","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=5194"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5194\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5194"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5194"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5194"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}