How to Resolve ORA-00918: Ambiguous Column Definitions in SELECT * Queries?

*Troubleshooting ORA-00918: Ambiguous Column Names in SELECT Queries**

The ORA-00918 error ("ambiguous column definitions") frequently arises when using SELECT * in SQL queries involving multiple tables with identically named columns. This ambiguity occurs because the query's result set would contain duplicate column names.

The solution is straightforward: explicitly specify the columns you need in your SELECT statement. Instead of SELECT *, list the columns individually, referencing the table they belong to:

<code class="language-sql">SELECT coaches.id, people.name, users.email, coaches.team_id
FROM ... -- Your JOIN clauses here</code>

Alternatively, employ column aliases to provide unique names for ambiguous columns:

<code class="language-sql">SELECT coaches.id AS coach_id, people.name, users.email, coaches.team_id AS coach_team_id
FROM ... -- Your JOIN clauses here</code>

By clearly defining each column, either through explicit naming or aliases, you eliminate the ambiguity and prevent the ORA-00918 error.

It's best practice to avoid SELECT * altogether, especially in complex queries with joins. Explicitly naming columns improves readability, maintainability, and query performance. This is particularly crucial when dealing with multiple tables that share column names.

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