MySQL UpdateField

CREATE PROCEDURE [dbo].[crud_tst-mysql_updateField]
    @itemID int,
    @field nvarchar(64),
    @value nvarchar(max),
    @username nvarchar(64)
AS
BEGIN

declare @sql nvarchar(max) = ''

if(@field = 'p1') begin
    set @sql = '
       update openquery(MYSQL1, ''select data1 from RemotelyCreatedTable where id = '+cast(@itemID as nvarchar)+''' )
        set data1='''+@value+'''
        where data1 <> '''+@value+'''
    '
    EXEC (@sql)

end else if(@field = 'p2') begin
    set @sql = '
       update openquery(MYSQL1, ''select data2 from RemotelyCreatedTable where id = '+cast(@itemID as nvarchar)+''' )
        set data2='''+@value+'''
        where data2 <> '''+@value+'''
    '
    EXEC (@sql)
end else begin
    select 'Невалидный код свойства' Msg, 0 Result
    return
end
select '' Msg, 1 Result

END