Question

您好我删除行时遇到问题，我想在数据库中保留两行并删除所有其他行我在此链接中找到了一个查询for delete row 但它给出了mysql语法限制功能。但在oracle中没有可用的限制变量。我怎么能这样做？

DELETE FROM Table
  WHERE DateColumn NOT IN (SELECT DateColumn 
                             FROM Table 
                         GROUP BY date(DateColumn) 
                         ORDER BY DateColumn DESC
                            LIMIT 2);

Answer 1

使用ROWID，ROWNUM和子查询这样的（未经测试）

delete from table WHERE rowid NOT IN
    (SELECT rowid FROM (SELECT rowid
                          FROM Table 
                         ORDER BY DateColumn DESC)
     WHERE rownum <= 2);

注意＆＃34; double＆＃34;选择是必要的，因为rownum与顺序混淆，因为它在rownum之后应用

如果日期不重要而您只想保留两行（随机），则可以简化为

delete from table WHERE rowid NOT IN
    (SELECT rowid FROM table WHERE rownum <= 2);

Answer 2

这个出租车可以通过这个查询实现

DELETE FROM TABLE 
 WHERE ROWID NOT IN
    (SELECT ROWIDS FROM (SELECT MIN(ROWID) ROWIDS 
                           FROM TABLE 
                          GROUP BY DATECOLUMN
                          ORDER BY DATECOLUMN DESC)
      WHERE ROWNUM <= 2);

最内层的查询将从表中返回rowid的min，然后立即外部查询将在最外面的删除中仅选择要避免的两行。

Answer 3

DELETE FROM Table
  WHERE DateColumn NOT IN (SELECT DateColumn 
                             FROM Table 
                             Where ROWNUM < 3
                             GROUP BY date(DateColumn) 
                             ORDER BY DateColumn DESC
                            );

我没有oracle客户端来运行查询。您可以在Oracle中使用ROWNUM，因为ORACLE中没有LIMIT

删除oracle中除前两行之外的所有行

3 个答案: