identifier - cheeyoung/sqlplus-public GitHub Wiki
ORA-00904: string: invalid identifier
Cause: The identifier or column name entered was invalid.
Action: Enter a valid identifier or column name. A valid identifier must begin with a letter, be less than or equal to 128 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 must not be a reserved word, unless it is enclosed in double quotation marks. If double quotation marks and mixed case were used for a column name when creating the table, then references to that column must use matching case and quotation marks.
ORA-01740: missing double quote in identifier
...
ORA-01741: illegal zero-length identifier
Cause: An attempt was made to use two double quotes ("") as an identifier. An identifier must be at least one character long.
Action: insert at least one character between the double quotes in the identifier. If a blank identifier is required, specify a blank space between the double quotes (" ").