C# 使用C在MYSQL中声明局部变量时发生致命错误

在MYSQL中声明局部变量时出现异常。请告诉我如何解决这个问题

例外情况： 在命令执行期间遇到致命错误。 内部异常： {必须定义参数'@OrderofParent'

代码Snippit:

加 允许用户变量=True

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在连接字符串参数中，实际调用mySQL的代码在哪里？

   StringBuilder sbQuery = new StringBuilder(); <br>
    sbQuery.Append(@"Declare @OrderofParent INT; SET @OrderofParent = 0;
                    select top 1 @OrderofParent = OrderofParent from Filter group        by          OrderofParent order by OrderofParent desc;

    select 'FamilyType' as Mode, 0 as Id, 'Complexity Type' as FilterName, null as FilterCreatedDate, 0 as IsDisabled,0 as ParentId,                                               @OrderofParent as OrderofParent,1 as TagDisplay, 0 as ParentCount from I_FamilyTypePrice
union
Select 'Filter', Id, FilterName, FilterCreatedDate, IsDisabled, f.ParentId, OrderofParent, TagDisplay, 0 from Filter f where f.ParentID = 0 
union
select 'FamilyType', ft.Id, FamilyTypeName, CreatedDate, 0,0, @OrderofParent,0, count(complexityType) from I_FamilyTypePrice ft join Family f on f.complexityType = ft.Id where version = @version and IsActive = 1 and Uploaded = 1; ");