Why is the GETDATE() an invalid identifier

I think you want SYSDATE, not GETDATE(). Try it:

UPDATE TableName SET LastModifiedDate = (SELECT SYSDATE FROM DUAL);

oracle function triggers

Use ORACLE equivalent of getdate() which is sysdate . Read about here.Getdate() belongs to SQL Server , will not work on Oracle.

Other option is current_date

oracle function triggers

getdate() for MS-SQL, sysdate for Oracle server

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