sql - 如何获取Oracle表的最后一行

Question

我想获取最后一行，我将其插入到 Oracle 11g Express 数据库的表中。我怎样才能做到这一点？

Answer 1

表中没有“最后”行这样的东西，因为 Oracle 表没有顺序的概念。

然而，假设你想找到最后插入的主键并且这个主键是一个递增的数字，你可以这样做：

select *
  from ( select a.*, max(pk) over () as max_pk
           from my_table a
                )
 where pk = max_pk

如果您有每行的创建日期，如果列名为created：

select *
  from ( select a.*, max(created) over () as max_created
           from my_table a
                )
 where created = max_created

或者，您可以使用聚合查询，例如：

select *
  from my_table
 where pk = ( select max(pk) from my_table )

这是一个小SQL Fiddle来演示。

Answer 2

SELECT * FROM (
    SELECT * FROM table_name ORDER BY sortable_column DESC
) WHERE ROWNUM = 1;

Answer 3

select * from table_name ORDER BY primary_id DESC FETCH FIRST 1 ROWS ONLY;

这是最简单的，不做子查询

Answer 4

最后一行根据复合键 K(k1, ..., kn) 上的严格总顺序：

SELECT  *
FROM    TableX AS o
WHERE   NOT EXISTS (
            SELECT  *
            FROM    TableX AS i
            WHERE   i.k1 > o.k1
                OR  (i.k1 = o.k1 AND i.k2 > o.k2)
                ...
                OR  (i.k1 = o.k1 AND i.k2 = o.k2 AND i.k3 = o.k3 AND ... AND i.kn > o.kn)
        )
;

考虑到 K 是简单的（即不是复合的）的特殊情况，上面的内容被缩短为：

SELECT  *
FROM    TableX AS o
WHERE   NOT EXISTS (
            SELECT  *
            FROM    TableX AS i
            WHERE   i.k1 > o.k1
        )
;

请注意，要使此查询仅返回一行，键必须在没有关系的情况下进行排序。如果允许关联，则此查询将返回与最大键关联的所有行。

Answer 5

你可以这样做：

SELECT * FROM (SELECT your_table.your_field, versions_starttime
               FROM your_table
               VERSIONS BETWEEN TIMESTAMP MINVALUE AND MAXVALUE)
WHERE ROWNUM = 1;

或者：

SELECT your_field,ora_rowscn,scn_to_timestamp(ora_rowscn) from your_table WHERE ROWNUM = 1;

Answer 6

SELECT * FROM 
  MY_TABLE
WHERE 
  <your filters>
ORDER BY PRIMARY_KEY DESC FETCH FIRST ROW ONLY

Answer 7

$sql = "INSERT INTO table_name( field1, field2 )  VALUES ('foo','bar') 
        RETURNING ID INTO :mylastid";
$stmt = oci_parse($db, $sql);
oci_bind_by_name($stmt, "mylastid", $last_id, 8, SQLT_INT);
oci_execute($stmt);

echo "last inserted id is:".$last_id;

---

提示：您必须在下面的 {your_id_col_name} 中使用您的 id 列名...

"RETURNING {your_id_col_name} INTO :mylastid"