CONVERT() is specific to T-SQL. CAST() is ANSI standard.
CONVERT function is specific to T-SQL and is not part of the ANSI standard. If you require a function that is platform agnostic then you would be better off using the
CAST function as it is compatible with other database platforms. SQL Convert Function Examples and Alternatives [mssqltips.com].
Current DateTime in YYYY-MM-DD HH:MM:SS Format
1 AS [column2],
CONVERT(varchar(30), GETDATE() ) AS [column3]
SELECT CONVERT(varchar(30), GETDATE() ) AS [column3] FROM [sourceTableName]