CREATEFUNCTIONget_multiple_values()RETURNSVARCHAR(255)BEGINDECLAREdoneINTDEFAULTFALSE;DECLAREaINT;DECLAREbINT;DECLAREcINT;DECLAREcurCURSORFORSELECTid,name,ageFROMusers;DECLARECONTINUEHANDLERFORNOTFOUNDSETdone=T
CREATE FUNCTION get_multiple_values() RETURNS CHAR BEGIN DECLARE value1 CHAR; DECLARE value2 CHAR;-- 逻辑处理 SET value1 = 'Value1'; SET value2 = 'Value2';RETURN CONCAT(value1, ',', value2);END 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 在上面的代码中,我们创建了一...
MySQL中的自定义函数(User-Defined Function, UDF)允许用户创建自己的函数,以便在SQL查询中使用。自定义函数可以返回单个值或多个值。返回多个值的函数通常通过返回一个表或数组来实现。 相关优势 代码复用:自定义函数可以在多个查询中重复使用,减少代码重复。 简化查询:复杂的逻辑可以通过函数封装,使SQL查询更加简洁。
data is found at the path given; this clause takes one of the following values: NULL ON EMPTY: The function returns NULL; this is the default ON EMPTYbehavior. DEFAULT value ON EMPTY: the provided value is returned. The values type must match that of the return type. ERROR ...
If it is possible that those arguments could return multiple values, the matched values are autowrapped as an array, in the order corresponding to the paths that produced them. Otherwise, the return value is the single matched value. mysql> SELECT JSON_EXTRACT('[10, 20, [30, 40]]', ...
本章列出了当你用任何主机语言调用MySQL时可能出现的错误。首先列出了服务器错误消息。其次列出了客户端程序消息 B.1. 服务器错误代码和消息 服务器错误信息来自下述源文件: · 错误消息信息列在share/errmsg.txt文件中。“%d”和“%s”分别代表编号和字符串,显示时,它们将被消息值取代。 · 错误值列在share/errm...
Before MySQL 5.0.10, stored functions created withCREATE FUNCTIONmust not contain references to tables, with limited exceptions. They may include someSETstatements that contain table references, for exampleSET a:= (SELECT MAX(id) FROM t), andSELECTstatements that fetch values directly into variables...
';varmodSqlParams=['菜鸟移动站','https://m.runoob.com',6];//改connection.query(modSql,modSqlParams,function(err,result){if(err){console.log('[UPDATE ERROR] -',err.message);return;}console.log('---UPDATE---');console.log('UPDATE affectedRows',result.affectedRows);console.log('--...
Returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. The result is a BIGINT value. If there are no matching rows,COUNT()returns 0.COUNT(NULL)returns 0. This function executes as a window function if over_clause is present. over_clause...
This library is written in typescript and provides its own types. For added convenience, methods that return rows or values will accept a generic so that you can specify the return type you expect: interfaceBook{id:numbertitle:stringisbn:string}constrow=awaitdb.getrow<Book>('SELECT id, title...