How do I Convert my Store procedure from MS-SQL to MySQL ?

USE [LoginDB]
GO
/****** Object:  StoredProcedure [dbo].[Validate_User]    Script Date: 08/24/2014 15:29:59 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER  PROCEDURE [dbo].[Validate_User]
	@Username NVARCHAR(20),
	@Password NVARCHAR(20)
AS
BEGIN
	SET NOCOUNT ON;
	DECLARE @UserId INT, @LastLoginDate DATETIME
	
	SELECT @UserId = UserId, @LastLoginDate = LastLoginDate 
	FROM Users WHERE Username = @Username AND [Password] = @Password
	
	IF @UserId IS NOT NULL
	BEGIN
		IF NOT EXISTS(SELECT UserId FROM UserActivation WHERE UserId = @UserId)
		BEGIN
			UPDATE Users
			SET LastLoginDate =  GETDATE()
			WHERE UserId = @UserId
			SELECT @UserId [UserId] -- User Valid
		END
		ELSE
		BEGIN
			SELECT -2 -- User not activated.
		END
	END
	ELSE
	BEGIN
		SELECT -1 -- User invalid.
	END
END