{"id":5895,"date":"2024-11-14T11:01:05","date_gmt":"2024-11-14T03:01:05","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5895\/"},"modified":"2024-11-14T11:01:05","modified_gmt":"2024-11-14T03:01:05","slug":"sql%e8%af%ad%e5%8f%a5ifelse%e6%80%8e%e4%b9%88%e7%94%a8","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5895\/","title":{"rendered":"sql\u8bed\u53e5ifelse\u600e\u4e48\u7528"},"content":{"rendered":"<blockquote><p>\n  ifelse \u8bed\u53e5\u662f\u4e00\u79cd\u6761\u4ef6\u8bed\u53e5\uff0c\u7528\u4e8e\u6839\u636e\u6761\u4ef6\u8bc4\u4f30\u7ed3\u679c\u8fd4\u56de\u4e0d\u540c\u503c\u3002\u5176\u8bed\u6cd5\u7ed3\u6784\u4e3a\uff1aif (condition) then return_value_if_condition_is_true else return_value_if_condition_is_false end if;\u3002\n<\/p><\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/202406\/03\/2024060321515873139.jpg\" class=\"aligncenter\" title=\"sql\u8bed\u53e5ifelse\u600e\u4e48\u7528\u63d2\u56fe\" alt=\"sql\u8bed\u53e5ifelse\u600e\u4e48\u7528\u63d2\u56fe\" \/><\/p>\n<p><strong>IFELSE \u8bed\u53e5\u5728 SQL \u4e2d\u7684\u4f7f\u7528<\/strong><\/p>\n<p>IFELSE \u8bed\u53e5\u662f\u4e00\u79cd\u6761\u4ef6\u8bed\u53e5\uff0c\u7528\u4e8e\u6839\u636e\u7ed9\u5b9a\u7684\u6761\u4ef6\u8bc4\u4f30\u7ed3\u679c\u6765\u8fd4\u56de\u4e0d\u540c\u7684\u503c\u3002\u5176\u8bed\u6cd5\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n<pre>IF (condition) THEN\n    return_value_if_condition_is_true\nELSE\n    return_value_if_condition_is_false\nEND IF;<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p><strong>\u5982\u4f55\u4f7f\u7528 IFELSE \u8bed\u53e5<\/strong><\/p>\n<ol>\n<li>\n<p>\u5728 IF \u90e8\u5206\uff0c\u6307\u5b9a\u9700\u8981\u8bc4\u4f30\u7684\u6761\u4ef6\u3002\u6761\u4ef6\u53ef\u4ee5\u662f\u4efb\u4f55\u5e03\u5c14\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li>column_name = &#8216;value&#8217;<\/li>\n<li>column_name IS NULL<\/li>\n<li>value1 &gt; value2<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>\u5728 THEN \u90e8\u5206\uff0c\u6307\u5b9a\u5982\u679c\u6761\u4ef6\u4e3a\u771f\u65f6\u8981\u8fd4\u56de\u7684\u503c\u3002\u8fd9\u53ef\u4ee5\u662f\u4efb\u4f55\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li>&#8216;true&#8217;<\/li>\n<li>1<\/li>\n<li>column_name<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>\u5728 ELSE \u90e8\u5206\uff0c\u6307\u5b9a\u5982\u679c\u6761\u4ef6\u4e3a\u5047\u65f6\u8981\u8fd4\u56de\u7684\u503c\u3002\u8fd9\u4e5f\u53ef\u4ee5\u662f\u4efb\u4f55\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li>&#8216;false&#8217;<\/li>\n<li>0<\/li>\n<li>NULL<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p><strong>\u793a\u4f8b<\/strong><\/p>\n<p>\u4ee5\u4e0b\u67e5\u8be2\u4f7f\u7528 IFELSE \u8bed\u53e5\u6765\u786e\u5b9a\u7ed9\u5b9a\u5ba2\u6237\u7684\u8ba2\u5355\u72b6\u6001\uff1a<\/p>\n<pre>SELECT customer_id, order_id,\n    IF(order_status = 'Shipped', '\u5df2\u53d1\u8d27', '\u672a\u53d1\u8d27') AS order_status\nFROM orders;<\/pre>\n<p> \u767b\u5f55\u540e\u590d\u5236 <\/p>\n<p>\u6b64\u67e5\u8be2\u5c06\u8fd4\u56de\u4e00\u4e2a\u7ed3\u679c\u96c6\uff0c\u5176\u4e2d\u6bcf\u884c\u7684 order_status \u5217\u663e\u793a\u8ba2\u5355\u7684\u5f53\u524d\u72b6\u6001\uff0c\u5373 &#8220;\u5df2\u53d1\u8d27&#8221; \u6216 &#8220;\u672a\u53d1\u8d27&#8221;\u3002<\/p>\n<p><strong>\u6ce8\u610f\u4e8b\u9879<\/strong><\/p>\n<ul>\n<li>IFELSE \u8bed\u53e5\u53ef\u4ee5\u5d4c\u5957\uff0c\u4ee5\u5904\u7406\u66f4\u590d\u6742\u7684\u6761\u4ef6\u3002<\/li>\n<li>\u5982\u679c\u6761\u4ef6\u4e3a NULL\uff0c\u5219\u8fd4\u56de NULL \u503c\u3002<\/li>\n<li>IFELSE \u8bed\u53e5\u901a\u5e38\u4e0e CASE \u8bed\u53e5\u4ea4\u66ff\u4f7f\u7528\uff0c\u8fd9\u63d0\u4f9b\u4e86\u66f4\u7075\u6d3b\u7684\u6761\u4ef6\u5904\u7406\u3002<\/li>\n<\/ul>\n<p>\u4ee5\u4e0a\u5c31\u662fifelse\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":"<p>ifelse \u8bed\u53e5\u662f\u4e00\u79cd\u6761\u4ef6\u8bed\u53e5\uff0c\u7528\u4e8e\u6839\u636e\u6761\u4ef6\u8bc4\u4f30\u7ed3\u679c\u8fd4\u56de\u4e0d\u540c\u503c\u3002\u5176\u8bed\u6cd5\u7ed3\u6784\u4e3a\uff1aif (condition) then return_value_if_condition_is_true else return_value_if_condition_is_false end if;\u3002 IFELSE \u8bed\u53e5\u5728 SQL \u4e2d\u7684\u4f7f\u7528 IFELSE \u8bed\u53e5\u662f\u4e00\u79cd\u6761\u4ef6\u8bed\u53e5\uff0c\u7528\u4e8e\u6839\u636e\u7ed9\u5b9a\u7684\u6761\u4ef6\u8bc4\u4f30\u7ed3\u679c\u6765\u8fd4\u56de\u4e0d\u540c\u7684\u503c\u3002\u5176\u8bed\u6cd5\u7ed3\u6784\u5982\u4e0b\uff1a IF (condition) THEN return_value_if_condition_is_true ELSE return_value_if_condition_is_false END IF; \u767b\u5f55\u540e\u590d\u5236 \u5982\u4f55\u4f7f\u7528 IFELSE \u8bed\u53e5 \u5728 IF \u90e8\u5206\uff0c\u6307\u5b9a\u9700\u8981\u8bc4\u4f30\u7684\u6761\u4ef6\u3002\u6761\u4ef6\u53ef\u4ee5\u662f\u4efb\u4f55\u5e03\u5c14\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a column_name = &#8216;value&#8217; column_name IS NULL value1 &gt; value2 \u5728 THEN \u90e8\u5206\uff0c\u6307\u5b9a\u5982\u679c\u6761\u4ef6\u4e3a\u771f\u65f6\u8981\u8fd4\u56de\u7684\u503c\u3002\u8fd9\u53ef\u4ee5\u662f\u4efb\u4f55\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a &#8216;true&#8217; 1 column_name \u5728 ELSE \u90e8\u5206\uff0c\u6307\u5b9a\u5982\u679c\u6761\u4ef6\u4e3a\u5047\u65f6\u8981\u8fd4\u56de\u7684\u503c\u3002\u8fd9\u4e5f\u53ef\u4ee5\u662f\u4efb\u4f55\u8868\u8fbe\u5f0f\uff0c\u4f8b\u5982\uff1a &#8216;false&#8217; 0 NULL \u793a\u4f8b \u4ee5\u4e0b\u67e5\u8be2\u4f7f\u7528 IFELSE \u8bed\u53e5\u6765\u786e\u5b9a\u7ed9\u5b9a\u5ba2\u6237\u7684\u8ba2\u5355\u72b6\u6001\uff1a [&hellip;]<\/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-5895","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5895","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=5895"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5895\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5895"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5895"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5895"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}