{"id":5790,"date":"2024-11-14T11:24:29","date_gmt":"2024-11-14T03:24:29","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5790\/"},"modified":"2024-11-14T11:24:29","modified_gmt":"2024-11-14T03:24:29","slug":"mysql-if-exists%e6%80%8e%e4%b9%88%e7%94%a8","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5790\/","title":{"rendered":"mysql\u00a0if exists\u600e\u4e48\u7528"},"content":{"rendered":"

\n if exists \u5728 mysql \u4e2d\u7528\u4e8e\u68c0\u67e5\u6570\u636e\u5e93\u5bf9\u8c61\u662f\u5426\u5b58\u5728\uff0c\u5728\u8bed\u53e5\u4e2d\u6267\u884c\u64cd\u4f5c\u524d\u63d0\u662f\u8be5\u5bf9\u8c61\u5b58\u5728\u3002\u5177\u4f53\u7528\u6cd5\u5982\u4e0b\uff1a\u8bed\u6cd5\uff1aif exists \u5bf9\u8c61\u540d\u79f0\u4f5c\u7528\uff1a\u5982\u679c\u5bf9\u8c61\u5b58\u5728\uff0c\u5219\u6267\u884c\u64cd\u4f5c\uff0c\u5426\u5219\u5ffd\u7565\u64cd\u4f5c\u3002\u7528\u9014\uff1a\u7528\u4e8e\u5728\u521b\u5efa\u5bf9\u8c61\u6216\u6267\u884c\u64cd\u4f5c\u524d\u68c0\u67e5\u5bf9\u8c61\u662f\u5426\u5b58\u5728\u3002\n<\/p><\/blockquote>\n

\"mysql\u00a0if<\/p>\n

IF EXISTS \u5728 MySQL \u4e2d\u7684\u4f7f\u7528<\/strong><\/p>\n

IF EXISTS \u662f MySQL \u4e2d\u7684\u4e00\u4e2a\u5173\u952e\u5b57\uff0c\u7528\u4e8e\u5728\u521b\u5efa\u8868\u6216\u5176\u4ed6\u6570\u636e\u5e93\u5bf9\u8c61\u65f6\u68c0\u67e5\u8be5\u5bf9\u8c61\u662f\u5426\u5b58\u5728\u3002<\/p>\n

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

IF EXISTS \u5bf9\u8c61\u540d\u79f0<\/pre>\n
 \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
\u5176\u4e2d\uff0c\u5bf9\u8c61\u540d\u79f0\u53ef\u4ee5\u662f\u8868\u3001\u89c6\u56fe\u3001\u5b58\u50a8\u8fc7\u7a0b\u6216\u5176\u4ed6\u6570\u636e\u5e93\u5bf9\u8c61\u3002<\/p>\n
\u4f5c\u7528<\/strong><\/p>\n
IF EXISTS \u8bed\u53e5\u7684\u4f5c\u7528\u662f\uff1a<\/p>\n
    \n
  • \u5982\u679c\u6307\u5b9a\u7684\u5bf9\u8c61\u5df2\u7ecf\u5b58\u5728\uff0c\u5219\u6267\u884c\u8bed\u53e5\u4e2d\u7684\u64cd\u4f5c\u3002<\/li>\n
  • \u5982\u679c\u6307\u5b9a\u7684\u5bf9\u8c61\u4e0d\u5b58\u5728\uff0c\u5219\u5ffd\u7565\u8bed\u53e5\u4e2d\u7684\u64cd\u4f5c\u3002<\/li>\n<\/ul>\n
    \u7528\u6cd5<\/strong><\/p>\n
    \u901a\u5e38\uff0cIF EXISTS \u8bed\u53e5\u7528\u4e8e\u5728\u6267\u884c\u521b\u5efa\u8bed\u53e5\u6216\u5176\u4ed6\u64cd\u4f5c\u4e4b\u524d\u68c0\u67e5\u5bf9\u8c61\u662f\u5426\u5b58\u5728\u3002\u8fd9\u53ef\u4ee5\u9632\u6b62\u521b\u5efa\u91cd\u590d\u7684\u5bf9\u8c61\u6216\u6267\u884c\u4e0d\u5fc5\u8981\u7684\u64cd\u4f5c\u3002<\/p>\n
    \u793a\u4f8b<\/strong><\/p>\n
    \u4ee5\u4e0b\u793a\u4f8b\u6f14\u793a\u4e86 IF EXISTS \u8bed\u53e5\u7684\u7528\u6cd5\uff1a<\/p>\n
    -- \u5982\u679c users \u8868\u4e0d\u5b58\u5728\uff0c\u5219\u521b\u5efa\u5b83\nIF NOT EXISTS users (\n    id INT NOT NULL AUTO_INCREMENT,\n    name VARCHAR(255) NOT NULL,\n    email VARCHAR(255) NOT NULL,\n    PRIMARY KEY (id)\n)\nENGINE=InnoDB;<\/pre>\n
     \u767b\u5f55\u540e\u590d\u5236 <\/p>\n
    \u5728\u8be5\u793a\u4f8b\u4e2d\uff0c\u5982\u679c users \u8868\u5df2\u7ecf\u5b58\u5728\uff0c\u5219\u521b\u5efa\u8bed\u53e5\u5c06\u88ab\u5ffd\u7565\u3002\u5426\u5219\uff0c\u5c06\u521b\u5efa users \u8868\u3002<\/p>\n
    \u6ce8\u610f<\/strong><\/p>\n
      \n
    • IF EXISTS \u8bed\u53e5\u53ea\u80fd\u7528\u4e8e\u521b\u5efa\u8bed\u53e5\u3002<\/li>\n
    • \u5982\u679c\u8981\u68c0\u67e5\u5176\u4ed6\u7c7b\u578b\u7684\u5bf9\u8c61\uff08\u4f8b\u5982\u89c6\u56fe\u6216\u5b58\u50a8\u8fc7\u7a0b\uff09\uff0c\u53ef\u4ee5\u4f7f\u7528 EXISTS \u5173\u952e\u5b57\u3002<\/li>\n
    • IF EXISTS \u8bed\u53e5\u53ef\u4ee5\u4e0e\u5176\u4ed6\u6761\u4ef6\u7ec4\u5408\u4f7f\u7528\uff0c\u4ee5\u521b\u5efa\u66f4\u590d\u6742\u7684\u68c0\u67e5\u903b\u8f91\u3002<\/li>\n<\/ul>\n
      \u4ee5\u4e0a\u5c31\u662f if exists\u600e\u4e48\u7528\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":"
      if exists \u5728 mysql \u4e2d\u7528\u4e8e\u68c0\u67e5\u6570\u636e\u5e93\u5bf9\u8c61\u662f\u5426\u5b58\u5728\uff0c\u5728\u8bed\u53e5\u4e2d\u6267\u884c\u64cd\u4f5c\u524d\u63d0\u662f\u8be5\u5bf9\u8c61\u5b58\u5728\u3002\u5177\u4f53\u7528\u6cd5\u5982\u4e0b\uff1a\u8bed\u6cd5\uff1aif exists \u5bf9\u8c61\u540d\u79f0\u4f5c\u7528\uff1a\u5982\u679c\u5bf9\u8c61\u5b58\u5728\uff0c\u5219\u6267\u884c\u64cd\u4f5c\uff0c\u5426\u5219\u5ffd\u7565\u64cd\u4f5c\u3002\u7528\u9014\uff1a\u7528\u4e8e\u5728\u521b\u5efa\u5bf9\u8c61\u6216\u6267\u884c\u64cd\u4f5c\u524d\u68c0\u67e5\u5bf9\u8c61\u662f\u5426\u5b58\u5728\u3002 IF EXISTS \u5728 MySQL \u4e2d\u7684\u4f7f\u7528 IF EXISTS \u662f MySQL \u4e2d\u7684\u4e00\u4e2a\u5173\u952e\u5b57\uff0c\u7528\u4e8e\u5728\u521b\u5efa\u8868\u6216\u5176\u4ed6\u6570\u636e\u5e93\u5bf9\u8c61\u65f6\u68c0\u67e5\u8be5\u5bf9\u8c61\u662f\u5426\u5b58\u5728\u3002 \u8bed\u6cd5 IF EXISTS \u5bf9\u8c61\u540d\u79f0 \u767b\u5f55\u540e\u590d\u5236 \u5176\u4e2d\uff0c\u5bf9\u8c61\u540d\u79f0\u53ef\u4ee5\u662f\u8868\u3001\u89c6\u56fe\u3001\u5b58\u50a8\u8fc7\u7a0b\u6216\u5176\u4ed6\u6570\u636e\u5e93\u5bf9\u8c61\u3002 \u4f5c\u7528 IF EXISTS \u8bed\u53e5\u7684\u4f5c\u7528\u662f\uff1a \u5982\u679c\u6307\u5b9a\u7684\u5bf9\u8c61\u5df2\u7ecf\u5b58\u5728\uff0c\u5219\u6267\u884c\u8bed\u53e5\u4e2d\u7684\u64cd\u4f5c\u3002 \u5982\u679c\u6307\u5b9a\u7684\u5bf9\u8c61\u4e0d\u5b58\u5728\uff0c\u5219\u5ffd\u7565\u8bed\u53e5\u4e2d\u7684\u64cd\u4f5c\u3002 \u7528\u6cd5 \u901a\u5e38\uff0cIF EXISTS \u8bed\u53e5\u7528\u4e8e\u5728\u6267\u884c\u521b\u5efa\u8bed\u53e5\u6216\u5176\u4ed6\u64cd\u4f5c\u4e4b\u524d\u68c0\u67e5\u5bf9\u8c61\u662f\u5426\u5b58\u5728\u3002\u8fd9\u53ef\u4ee5\u9632\u6b62\u521b\u5efa\u91cd\u590d\u7684\u5bf9\u8c61\u6216\u6267\u884c\u4e0d\u5fc5\u8981\u7684\u64cd\u4f5c\u3002 \u793a\u4f8b \u4ee5\u4e0b\u793a\u4f8b\u6f14\u793a\u4e86 IF EXISTS \u8bed\u53e5\u7684\u7528\u6cd5\uff1a — \u5982\u679c users \u8868\u4e0d\u5b58\u5728\uff0c\u5219\u521b\u5efa\u5b83 IF NOT EXISTS users ( id INT NOT NULL AUTO_INCREMENT, name VARCHAR(255) NOT […]<\/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-5790","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5790","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=5790"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5790\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5790"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5790"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5790"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}