Why Am I Getting ORA-00904: Invalid Identifier in My Oracle SQL Query?

Troubleshooting ORA-00904: Invalid Identifier in Oracle Database

The ORA-00904 error typically indicates that the database cannot recognize an identifier used in an SQL statement. This error often occurs when attempting to fetch values from a table using a specific column value as a filter.

Problem:

A user reported encountering the ORA-00904 error while executing the following query:

select fname, lname 
from reg1 
where uname="bbb";

This query aims to retrieve the fname and lname columns from the reg1 table, where the uname column's value matches "bbb". However, the user received the error message:

ORA-00904: "bbb": invalid identifier

Solution:

The error points to the use of double quotes (") around the value "bbb" in the WHERE clause. In Oracle SQL, string literals must be enclosed in single quotes ('). To resolve the issue, the query should be modified as follows:

select fname, lname 
from reg1 
where uname='bbb';

By using single quotes around the string literal, the database will properly recognize "bbb" as a string value and execute the query successfully.

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