Mysql 函数从查询中返回一个值
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Mysql function returning a value from a query
提问by Cesar
i want to create a function which calculates a value using a query and I am having a problem returning the value:
我想创建一个使用查询计算值的函数，但在返回值时遇到问题：
Shortened, my query is:
缩短，我的查询是：
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.
我收到 SQL 语法错误。
SQL Error (1064): You have an error in your SQL syntax;
SQL 错误 (1064)：您的 SQL 语法有错误；
回答by theChrisKent
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.).
假设这些都是通用名称（表不会是一个好的表名），问题是你不能使用 == 进行比较。您还缺少一些关键语法（DECLARE、SELECT INTO 等）。
Change to this:
改成这样：
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
MySQL Comparison Functions and Operators
Related Question: Single Equals in MYSQL
相关问题：MYSQL 中的单等号
Function Help: http://www.databasejournal.com/features/mysql/article.php/3569846/MySQL-Stored-Functions.htm
函数帮助：http: //www.databasejournal.com/features/mysql/article.php/3569846/MySQL-Stored-Functions.htm
