如何解决 SQL SELECT * 查询中的 ORA-00918：'列定义不明确”？

*Oracle 错误 ORA-00918：解决 SELECT 语句中的不明确列**

执行涉及多个具有相同名称列的表的 SELECT * 查询通常会导致 ORA-00918 错误：“列定义不明确”。出现这种歧义是因为当多个表共享列名时，数据库无法确定要检索哪个表的列。

考虑这个例子：

<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>

以上是如何解决 SQL SELECT * 查询中的 ORA-00918：'列定义不明确”？的详细内容。更多信息请关注PHP中文网其他相关文章！