How do I convert this MSSQL stored procedure to a mysql stored procedure?

I'm starting out with stored procedures in mysql, but I'm used to mssql and have no idea how to add parameters and create mysql stored procedures. And yes, I checked tutorials on creating basic mysql stored procedures. Just not how to execute a string sql statement as can be seen in the example below.
Please help!



USE [tt]
GO
/****** Object: StoredProcedure [dbo].[_getNewsPagedSorted] Script Date: 6-11-2013 15:09:22 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

-- =============================================
-- Author: <Author,,Name>
-- Create date: <Create Date,,>
-- Description: <Description,,>
-- =============================================
ALTER PROCEDURE [dbo].[_getNewsPagedSorted]
@startRowIndex int
,@maximumRows int
,@sortExpression nvarchar(20)
,@Lang nvarchar(20)

AS
BEGIN
SET NOCOUNT ON;

if @sortExpression=''
set @sortExpression='publishdate DESC'

declare @sql nvarchar(max)

set @SQL='SELECT * FROM (select ROW_NUMBER() OVER (ORDER BY '+@sortExpression+') as RowNum,
* FROM news WHERE publishdate <=getdate() and lang=''' + @Lang + ''') as info
WHERE RowNum > '+STR(@startRowIndex)+' AND RowNum <= ('+STR(@startRowIndex + @maximumRows)+') '

EXEC sp_executesql @sql

 

show the result you are looking for and some sample data... then only will be possible to help you out