如何解決 SQL SELECT * 查詢中的 ORA-00918：「列定義不明確」？

*Oracle 錯誤 ORA-00918：解決 SELECT 語句中的不明確列**

執行涉及多個具有相同名稱列的表的 SELECT * 查詢通常會導致 ORA-00918 錯誤：「列定義不明確」。出現這種歧義是因為當多個表共享列名時，資料庫無法確定要檢索哪個表的列。

考慮這個例子：

<code class="language-sql">SELECT *
FROM
  (SELECT DISTINCT(coaches.id),
    people.*,
    users.*,
    coaches.*
  FROM "COACHES"
  INNER JOIN people ON people.id = coaches.person_id
  INNER JOIN users ON coaches.person_id = users.person_id
  LEFT OUTER JOIN organizations_users ON organizations_users.user_id = users.id
) WHERE rownum <p>To correct this, replace the ambiguous `SELECT *` with a specific column selection.  For instance:</p><p>Instead of selecting all columns (`SELECT *`), explicitly list the desired columns and use aliases to resolve ambiguity:</p>SELECT
  coaches.id AS COACHES_ID,
  people.name,
  users.email,
  coaches.team
FROM ...  -- Rest of your query remains the same

This approach assigns unique aliases (e.g., `COACHES_ID`) to each selected column, eliminating the ambiguity.  Alternatively, omit duplicate columns entirely, selecting only the necessary data.

Best practice dictates avoiding `SELECT *` in production SQL.  Explicitly defining columns enhances code clarity, maintainability, and reduces the risk of errors caused by ambiguous column names.</code>

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