Procedure expects parameter '@statement' of type 'ntext/nchar/nvarchar'.

DECLARE @SQL VARCHAR(100)
SET @SQL = 'SELECT TOP 1 * FROM sys.tables'
EXECUTE sp_executesql @SQL

DECLARE @SQL NVARCHAR(100)
SET @SQL = 'SELECT TOP 1 * FROM sys.tables'
EXECUTE sp_executesql @SQL

DECLARE @SQL NVARCHAR(100)
SET @SQL = N'SELECT TOP 1 * FROM sys.tables'
EXECUTE sp_executesql @SQL