How to Resolve the ORA-00904 Invalid Identifier Error in Oracle?

ORA-00904 Error Resolving: Understanding Invalid Identifier Issue

In Oracle, the ORA-00904 error typically occurs when an invalid identifier is used in a query. A common scenario where this error is encountered is when attempting to retrieve data from a table using a column name that is not properly quoted.

To understand the resolution, it is important to note that identifiers in Oracle, such as column names, must be enclosed in double quotes (" "). However, in the provided example, the username "bbb" is only enclosed in single quotes (').

Resolution:

The solution is to enclose the username "bbb" in double quotes, as follows:

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

By properly quoting the identifier, Oracle can recognize it as a valid column name and successfully execute the query. This syntax ensures that the database interprets "bbb" as a value rather than a column name.

Remember, always use double quotes when referencing column names in SQL queries to avoid such errors.

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