{"id":207082,"date":"2025-07-08T08:56:38","date_gmt":"2025-07-08T00:56:38","guid":{"rendered":"https:\/\/server.hk\/cnblog\/207082\/"},"modified":"2025-07-08T08:56:38","modified_gmt":"2025-07-08T00:56:38","slug":"%e5%a6%82%e4%bd%95%e5%a3%b0%e6%98%8e%e4%b8%80%e4%b8%aasql%e8%a1%8c%ef%bc%8cif-else%e8%af%ad%e5%8f%a5%e6%9c%aa%e5%a3%b0%e6%98%8e%e9%97%ae%e9%a2%98","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/207082\/","title":{"rendered":"\u5982\u4f55\u58f0\u660e\u4e00\u4e2aSQL\u884c\uff0cif else\u8bed\u53e5\u672a\u58f0\u660e\u95ee\u9898"},"content":{"rendered":"

<\/b> <\/p>\n

\u5f53\u524d\u4f4d\u7f6e\uff1a ><\/span> ><\/span> ><\/span> ><\/span> \u5982\u4f55\u58f0\u660e\u4e00\u4e2aSQL\u884c\uff0cif else\u8bed\u53e5\u672a\u58f0\u660e\u95ee\u9898<\/span><\/p>\n

\u6765\u6e90\uff1astackoverflow<\/span>
\n2024-04-19 22:18:36<\/span>
\n<\/i>0\u6d4f\u89c8<\/span>
\n<\/i>\u6536\u85cf<\/span> <\/p>\n

\u5927\u5bb6\u597d\uff0c\u6211\u4eec\u53c8\u89c1\u9762\u4e86\u554a~\u672c\u6587\u300a\u5982\u4f55\u58f0\u660e\u4e00\u4e2aSQL\u884c\uff0cif else\u8bed\u53e5\u672a\u58f0\u660e\u95ee\u9898\u300b<\/span>\u7684\u5185\u5bb9\u4e2d\u5c06\u4f1a\u6d89\u53ca\u5230<\/span>\u7b49\u7b49\u3002\u5982\u679c\u4f60\u6b63\u5728\u5b66\u4e60Golang<\/span>\u76f8\u5173\u77e5\u8bc6\uff0c\u6b22\u8fce\u5173\u6ce8\u6211\uff0c\u4ee5\u540e\u4f1a\u7ed9\u5927\u5bb6\u5e26\u6765\u66f4\u591aGolang<\/span>\u76f8\u5173\u6587\u7ae0\uff0c\u5e0c\u671b\u6211\u4eec\u80fd\u4e00\u8d77\u8fdb\u6b65\uff01\u4e0b\u9762\u5c31\u5f00\u59cb\u672c\u6587\u7684\u6b63\u5f0f\u5185\u5bb9~<\/p>\n

\u95ee\u9898\u5185\u5bb9
\n <\/p>\n

\u6211\u6709\u4e00\u4e2a\u50cf\u4e0b\u9762\u8fd9\u6837\u7684\u4ee3\u7801\u3002<\/p>\n

var sql string\n\nif pnt.type == \"newtype\" {\n    sql = `select code, count(*) count from ( \n                select code \n                    from code_table \n                    where start >= ? and end <= ? \n                union \n                select code \n                    from code_table \n                    where start >= ? and end <= ? \n                ) a group by code`\n    rows, err := pnt.readconn(\"testdb\").query(sql, start, end, start, end)\n} else {\n    sql = `select code, count(*) count from code_table where start >= ? and end <= ?` group by code\n    rows, err := pnt.readconn(\"testdb\").query(sql, start, end)\n}\n\nif err == nil {\n    defer rows.close()\n    for rows.next() {\n        var code, count int\n        rows.scan(&code, &count)\n    }\n} else {\n    log.println(err)\n}<\/pre>\n
\u8fd9\u4f1a\u7ed9\u6211\u4e00\u4e2a\u7c7b\u4f3c\u8fd9\u6837\u7684\u9519\u8bef\u201c\u672a\u4e3a\u884c\u58f0\u660e\u53d8\u91cf\uff0c\u9519\u8bef\u201d… <\/p>\n
\u6211\u5c1d\u8bd5\u58f0\u660e\u201cvar err error\u201d\uff0c\u5e76\u5728 if else \u8bed\u53e5\u4e2d\u4f7f\u7528 = \u800c\u4e0d\u662f := \u50cf\u8fd9\u6837\u7684\u4e1c\u897f<\/p>\n
var err error\nrows, err = pnt.switchConn(\"base\", \"read\").Query(sql, start, end)<\/pre>\n
\u4f46\u662f\uff0c\u6211\u4ecd\u7136\u65e0\u6cd5\u58f0\u660e\u884c\uff0c\u56e0\u4e3a\u6211\u4f1a\u9047\u5230\u4e0d\u540c\u7c7b\u578b\u7684\u9519\u8bef\u3002\u6211\u5c1d\u8bd5\u5c06\u5176\u58f0\u660e\u4e3a\u5b57\u7b26\u4e32\uff0c\u4f46\u6ca1\u6709\u6210\u529f\u3002<\/p>\n
\u8fd9\u662f\u6211\u7b2c\u4e00\u6b21\u4f7f\u7528 golang\uff0cif else \u7684\u4e8b\u60c5\u8ba9\u6211\u5f88\u56f0\u96be\uff0c\u4e3a\u4ec0\u4e48\u6211\u4e0d\u80fd\u5728 if else \u8bed\u53e5\u4e2d\u4f7f\u7528 := \u3002\u6b63\u5982\u60a8\u6240\u770b\u5230\u7684\uff0c\u6211\u4e0d\u80fd\u5728 if else \u8bed\u53e5\u4e4b\u5916\u4f7f\u7528 rows, err := \uff0c\u56e0\u4e3a\u4e24\u8005\u90fd\u6709\u4e0d\u540c\u6570\u91cf\u7684\u53c2\u6570\u3002 <\/p>\n
 <\/p>\n
\u89e3\u51b3\u65b9\u6848<\/h2>\n
 <\/p>\n
\u7531\u4e8e\u53d8\u91cf\u7684\u8303\u56f4\uff0c\u60a8\u9047\u5230\u4e86\u95ee\u9898\u3002 \u5728 golang \u4e2d\uff0c:=<\/code> \u5728\u4f5c\u7528\u57df\u5185\u521b\u5efa\u4e00\u4e2a\u65b0\u53d8\u91cf\u3002<\/p>\n
rows, err := pnt.readconn(\"testdb\").query(sql, \u5f00\u59cb, \u7ed3\u675f, \u5f00\u59cb, \u7ed3\u675f)<\/code><\/p>\n
\u5728 if<\/code> \u5757\u4e2d\u521b\u5efa\u65b0\u7684 rows<\/code> \u548c err<\/code> \u53d8\u91cf\uff0c\u8fd9\u4e9b\u53d8\u91cf\u5728 if \u5757\u4e4b\u5916\u65e0\u6cd5\u8bbf\u95ee\u3002<\/p>\n<\/p>\n
\u4fee\u590d\uff0c<\/p>\n
var sql string\nvar err error\nvar rows *sql.Rows\n\nif pnt.Type == \"newType\" {\n    sql = `select code, count(*) count from ( \n                select code \n                    from code_table \n                    where start >= ? and end <= ? \n                union \n                select code \n                    from code_table \n                    where start >= ? and end <= ? \n                ) a group by code`\n    rows, err = pnt.ReadConn(\"testdb\").Query(sql, start, end, start, end)\n} else {\n    sql = `select code, count(*) count from code_table where start >= ? and end <= ?` group by code\n    rows, err = pnt.ReadConn(\"testdb\").Query(sql, start, end)\n}\n\nif err == nil {\n    defer rows.Close()\n    for rows.Next() {\n        var code, count int\n        rows.Scan(&code, &count)\n    }\n} else {\n    log.Println(err)\n}<\/pre>\n
\u5728golang\u4e2d\u201c:=\u201d\u610f\u5473\u7740\u4f60\u58f0\u660e\u4e00\u4e2a\u53d8\u91cf\u5e76\u4e3a\u5176\u5206\u914d\u4e00\u4e2a\u8fd9\u4e2a\u503cgo\u4f1a\u81ea\u52a8\u68c0\u6d4b\u4ed6\u7684\u7c7b\u578b\u6240\u4ee5\uff1a \u4f8b\u5b50 \u53d8\u91cf := 15<\/code> \u4e00\u6837\u7684 var \u53d8\u91cf int = 15<\/code> <\/p>\n
\u6240\u4ee5\u5f53\u4f60\u8fd9\u6837\u505a\u65f6 rows, err := pnt.switchconn(\"base\", \"read\").query(sql, start, end, start, end) } \u522b\u7684 { sql =<\/code>select code, count(*) \u4ece code_table \u4e2d\u8ba1\u6570\uff0c\u5176\u4e2d start >= ?\u5e76\u901a\u8fc7\u4ee3\u7801\u7ed3\u675f <= ?group rows, err := pnt.switchconn(\"base\", \"read\").query(sql, start, end) } \u5f2f\u5f2f\u5f2f\u5f2f \u60a8\u58f0\u660e\u76f8\u540c\u7684\u53d8\u91cf rows \u5e76\u72af\u4e86\u4e24\u6b21\u9519\u8bef <\/code><\/p>\n
\u4eca\u5929\u5173\u4e8e\u300a\u5982\u4f55\u58f0\u660e\u4e00\u4e2aSQL\u884c\uff0cif else\u8bed\u53e5\u672a\u58f0\u660e\u95ee\u9898\u300b\u7684\u5185\u5bb9\u4ecb\u7ecd\u5c31\u5230\u6b64\u7ed3\u675f\uff0c\u5982\u679c\u6709\u4ec0\u4e48\u7591\u95ee\u6216\u8005\u5efa\u8bae\uff0c\u53ef\u4ee5\u5728\u516c\u4f17\u53f7\u4e0b\u591a\u591a\u56de\u590d\u4ea4\u6d41\uff1b\u6587\u4e2d\u82e5\u6709\u4e0d\u6b63\u4e4b\u5904\uff0c\u4e5f\u5e0c\u671b\u56de\u590d\u7559\u8a00\u4ee5\u544a\u77e5\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5f53\u524d\u4f4d\u7f6e\uff1a > > ...<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4925],"tags":[],"class_list":["post-207082","post","type-post","status-publish","format-standard","hentry","category-4925"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/207082","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=207082"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/207082\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=207082"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=207082"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=207082"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}