Mysql函数从查询中返回一个值 [英] Mysql function returning a value from a query

问题描述

我想创建一个函数来计算一个使用查询的值，并且我有一个返回值的问题：

缩短了，我的查询是：

  CREATE FUNCTION func01（value1 INT，monto DECIMAL（10,2））RETURNS DECIMAL（10,2）
 BEGIN 
 SET @var_name = 0; 
从table where data_init = 1中选择@ var_name = if（value1 = 1，monto * table.divisa_dolar，table.monto * divisa_euro）; 
返回@var_nam; 
 END 
  

我得到一个SQL语法错误。

SQL错误（1064）：您的SQL语法错误;

解决方案

假设这些都是通用名称（表格不会是一个好的表名），问题是您无法使用==进行比较。您还缺少一些关键语法（DECLARE，SELECT INTO等）。

更改为：

 CREATE FUNCTION func01（value1 INT，monto DECIMAL（10,2））
 RETURNS DECIMAL（10,2）
 DETERMINISTIC 
 BEGIN 
 DECLARE var_name DECIMAL（10,2）; 
 SET var_name = 0; 
 SELECT if（value1 = 1，monto * divisa_dolar，monto * divisa_euro）INTO var_name 
 FROM table 
 WHERE data_init = 1; 
 RETURN var_name; 
 END 
  

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功能帮助：< a href =http://www.databasejournal.com/features/mysql/article.php/3569846/MySQL-Stored-Functions.htm =nofollow noreferrer> http://www.databasejournal.com/features /mysql/article.php/3569846/MySQL-Stored-Functions.htm

i want to create a function which calculates a value using a query and I am having a problem returning the value:

Shortened, my query is:

CREATE FUNCTION func01(value1 INT , monto DECIMAL (10,2)) RETURNS DECIMAL(10,2)
BEGIN
SET @var_name = 0;
select @var_name=if(value1 = 1,monto * table.divisa_dolar,table.monto *divisa_euro) from table where data_init = 1;
return @var_nam;
END

I get a SQL syntax error.

SQL Error (1064): You have an error in your SQL syntax;

解决方案

Assuming these are all generic names (table will not be a good table name), the problem is you can't use == for comparison. You are also missing some key syntax (DECLARE, SELECT INTO, etc.).

Change to this:

CREATE FUNCTION func01(value1 INT , monto DECIMAL (10,2))
RETURNS DECIMAL(10,2)
DETERMINISTIC
BEGIN
  DECLARE var_name DECIMAL(10,2);
  SET var_name = 0;
  SELECT if(value1 = 1,monto *divisa_dolar,monto *divisa_euro) INTO var_name
    FROM table
    WHERE data_init = 1;
  RETURN var_name;
END

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Related Question: Single Equals in MYSQL

Function Help: http://www.databasejournal.com/features/mysql/article.php/3569846/MySQL-Stored-Functions.htm

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