Migrating from SQL Server to MySQL using MySQL Workbench tool
Well, since you have data currently stored in SQL Server, and it's already in an NVARCHAR column, then either it's an NVARCHAR &lt;= 4000 (in which case you can't lose any data, and should just change all instances of NVARCHAR(8000) to NVARCHAR(4000)), or it's an NVARCHAR(MAX) column, in which case you change all instances of NVARCHAR(8000) to NVARCHAR(MAX). Or just leave out those CASTs - do you really need them?

As an aside, you should probably change as NTEXT to as NVARCHAR(MAX) as well.