{"id":6260,"date":"2024-11-14T11:09:38","date_gmt":"2024-11-14T03:09:38","guid":{"rendered":"https:\/\/fwq.ai\/blog\/6260\/"},"modified":"2024-11-14T11:09:38","modified_gmt":"2024-11-14T03:09:38","slug":"sql%e4%b8%addeclare%e7%9a%84%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/6260\/","title":{"rendered":"sql\u4e2ddeclare\u7684\u7528\u6cd5"},"content":{"rendered":"

sql \u4e2ddeclare\u7684\u7528\u6cd5<\/strong><\/p>\n

DECLARE \u5728 SQL \u4e2d\u662f\u4e00\u4e2a\u7528\u4e8e\u58f0\u660e\u53d8\u91cf\u7684\u8bed\u53e5\u3002\u53d8\u91cf\u662f\u7528\u4e8e\u5b58\u50a8\u5728\u7a0b\u5e8f\u6267\u884c\u671f\u95f4\u53ef\u4ee5\u66f4\u6539\u503c\u7684\u5360\u4f4d\u7b26\u3002DECLARE \u8bed\u53e5\u5141\u8bb8\u5f00\u53d1\u4eba\u5458\u5728\u7a0b\u5e8f\u4e2d\u521b\u5efa\u4e00\u4e2a\u53d8\u91cf\uff0c\u5e76\u6307\u5b9a\u5176\u6570\u636e\u7c7b\u578b\u548c\uff08\u53ef\u9009\uff09\u521d\u59cb\u503c\u3002<\/p>\n

\u8bed\u6cd5<\/strong><\/p>\n

DECLARE <\u53d8\u91cf\u540d> <\u6570\u636e\u7c7b\u578b> [DEFAULT <\u9ed8\u8ba4\u503c>];<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u53c2\u6570\u8bf4\u660e<\/strong><\/p>\n
    \n
  •  \uff1a<\/strong>\u58f0\u660e\u7684\u53d8\u91cf\u7684\u540d\u79f0\u3002<\/li>\n
  •  \uff1a<\/strong>\u53d8\u91cf\u7684\u6570\u636e\u7c7b\u578b\uff0c\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 SQL \u6570\u636e\u7c7b\u578b\u3002<\/li>\n
  •  [DEFAULT ]\uff1a<\/strong>\uff08\u53ef\u9009\uff09\u53d8\u91cf\u7684\u521d\u59cb\u503c\u3002\u5982\u679c\u672a\u6307\u5b9a\uff0c\u5219\u53d8\u91cf\u7684\u9ed8\u8ba4\u503c\u4e3a NULL\u3002<\/li>\n<\/ul>\n
    \u4f7f\u7528\u65b9\u6cd5<\/strong><\/p>\n
    \u8981\u58f0\u660e\u53d8\u91cf\u5e76\u4e3a\u5176\u5206\u914d\u503c\uff0c\u8bf7\u4f7f\u7528\u4ee5\u4e0b\u8bed\u6cd5\uff1a<\/p>\n
    DECLARE <\u53d8\u91cf\u540d> <\u6570\u636e\u7c7b\u578b> := <\u503c>;<\/pre>\n
     \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
    \u793a\u4f8b<\/strong><\/p>\n
    \u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u58f0\u660e\u4e86\u4e00\u4e2a\u540d\u4e3a @name \u7684\u53d8\u91cf\uff0c\u5176\u6570\u636e\u7c7b\u578b\u4e3a VARCHAR(50)\uff0c\u5e76\u5c06\u5176\u521d\u59cb\u503c\u8bbe\u7f6e\u4e3a “John Smith”:<\/p>\n
    DECLARE @name VARCHAR(50) DEFAULT 'John Smith';<\/pre>\n
     \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
    \u7528\u9014<\/strong><\/p>\n
    DECLARE \u8bed\u53e5\u5728\u5404\u79cd SQL \u573a\u666f\u4e2d\u90fd\u5f88\u6709\u7528\uff0c\u5305\u62ec\uff1a<\/p>\n
      \n
    • \u5b58\u50a8\u4e2d\u95f4\u7ed3\u679c\u6216\u8ba1\u7b97\u3002<\/li>\n
    • \u4f20\u9012\u53c2\u6570\u5230\u5b58\u50a8\u8fc7\u7a0b\u6216\u51fd\u6570\u3002<\/li>\n
    • \u521b\u5efa\u52a8\u6001\u67e5\u8be2\u3002<\/li>\n<\/ul>\n
      \u4f18\u70b9<\/strong><\/p>\n
      \u4f7f\u7528 DECLARE \u8bed\u53e5\u6709\u51e0\u4e2a\u4f18\u70b9\uff1a<\/p>\n
        \n
      • \u63d0\u9ad8\u548c\u53ef\u7ef4\u62a4\u6027\u3002<\/li>\n
      • \u4f18\u5316\u67e5\u8be2\u6027\u80fd\uff0c\u56e0\u4e3a SQL \u4f18\u5316\u5668\u53ef\u4ee5\u5bf9\u5305\u542b\u53d8\u91cf\u7684\u67e5\u8be2\u8fdb\u884c\u66f4\u597d\u7684\u4f18\u5316\u3002<\/li>\n
      • \u5141\u8bb8\u5728\u5b58\u50a8\u8fc7\u7a0b\u6216\u51fd\u6570\u4e2d\u4f7f\u7528\u52a8\u6001\u6570\u636e\u3002<\/li>\n<\/ul>\n
        \u4ee5\u4e0a\u5c31\u662fsql\u4e2ddeclare\u7684\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":"
        sql \u4e2ddeclare\u7684\u7528\u6cd5 DECLARE \u5728 SQL \u4e2d\u662f\u4e00\u4e2a\u7528\u4e8e\u58f0\u660e\u53d8\u91cf\u7684\u8bed\u53e5\u3002\u53d8\u91cf\u662f\u7528\u4e8e\u5b58\u50a8\u5728\u7a0b\u5e8f\u6267\u884c\u671f\u95f4\u53ef\u4ee5\u66f4\u6539\u503c\u7684\u5360\u4f4d\u7b26\u3002DECLARE \u8bed\u53e5\u5141\u8bb8\u5f00\u53d1\u4eba\u5458\u5728\u7a0b\u5e8f\u4e2d\u521b\u5efa\u4e00\u4e2a\u53d8\u91cf\uff0c\u5e76\u6307\u5b9a\u5176\u6570\u636e\u7c7b\u578b\u548c\uff08\u53ef\u9009\uff09\u521d\u59cb\u503c\u3002 \u8bed\u6cd5 DECLARE <\u53d8\u91cf\u540d> <\u6570\u636e\u7c7b\u578b> [DEFAULT <\u9ed8\u8ba4\u503c>]; \u767b\u5f55\u540e\u590d\u5236 \u53c2\u6570\u8bf4\u660e \uff1a\u58f0\u660e\u7684\u53d8\u91cf\u7684\u540d\u79f0\u3002 \uff1a\u53d8\u91cf\u7684\u6570\u636e\u7c7b\u578b\uff0c\u53ef\u4ee5\u662f\u4efb\u4f55\u6709\u6548\u7684 SQL \u6570\u636e\u7c7b\u578b\u3002 [DEFAULT ]\uff1a\uff08\u53ef\u9009\uff09\u53d8\u91cf\u7684\u521d\u59cb\u503c\u3002\u5982\u679c\u672a\u6307\u5b9a\uff0c\u5219\u53d8\u91cf\u7684\u9ed8\u8ba4\u503c\u4e3a NULL\u3002 \u4f7f\u7528\u65b9\u6cd5 \u8981\u58f0\u660e\u53d8\u91cf\u5e76\u4e3a\u5176\u5206\u914d\u503c\uff0c\u8bf7\u4f7f\u7528\u4ee5\u4e0b\u8bed\u6cd5\uff1a DECLARE <\u53d8\u91cf\u540d> <\u6570\u636e\u7c7b\u578b> := <\u503c>; \u767b\u5f55\u540e\u590d\u5236 \u793a\u4f8b \u5728\u4e0b\u9762\u7684\u793a\u4f8b\u4e2d\uff0c\u6211\u4eec\u58f0\u660e\u4e86\u4e00\u4e2a\u540d\u4e3a @name \u7684\u53d8\u91cf\uff0c\u5176\u6570\u636e\u7c7b\u578b\u4e3a VARCHAR(50)\uff0c\u5e76\u5c06\u5176\u521d\u59cb\u503c\u8bbe\u7f6e\u4e3a “John Smith”: DECLARE @name VARCHAR(50) DEFAULT ‘John Smith’; \u767b\u5f55\u540e\u590d\u5236 \u7528\u9014 DECLARE \u8bed\u53e5\u5728\u5404\u79cd SQL \u573a\u666f\u4e2d\u90fd\u5f88\u6709\u7528\uff0c\u5305\u62ec\uff1a \u5b58\u50a8\u4e2d\u95f4\u7ed3\u679c\u6216\u8ba1\u7b97\u3002 \u4f20\u9012\u53c2\u6570\u5230\u5b58\u50a8\u8fc7\u7a0b\u6216\u51fd\u6570\u3002 \u521b\u5efa\u52a8\u6001\u67e5\u8be2\u3002 \u4f18\u70b9 \u4f7f\u7528 DECLARE […]<\/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-6260","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/6260","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=6260"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/6260\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=6260"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=6260"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=6260"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}