Invalid or Nonexistent Column Name – ORA 00904

There are multiple reasons which can lead to this common error code.

Below, there are some scenarios which can occur.

• The column name entered is either missing or invalid.Enter a valid column name. A valid column name must begin with a letter, be less than or equal to 30 characters, and consist of only alphanumeric characters and the special characters $, _, and #. If it contains other characters, then it must be enclosed in double quotation marks. It may not be a reserved word.

• If you are copying column definition from some other table’s DDL statement and if the selected  column is not the last one you will also copy comma, and if you put it as last column in your DDL statement you will see “ORA-00904: invalid identifier”because after comma Oracle expect another column declaration.

• If you will see the error Schema Creation Failed: ORA-00904: invalid identifier. The reason is that your schema creation failed because AUDIT is a reserved word in Oracle 11g R2.+

• Apart from table creation, you will see error “ORA-00904: invalid identifier” if you use wrong column name in INSERT statement or use a non-existent column name. Most of the time it happens because of typo, but some other time it could be due to parallel update e.g. someone changed the schema of table and renamed or dropped the column you are referring in INSERT query.