Question

到目前为止，我编写了一个查询，将第一行拆分为多行，但后面N行的结果将是N行返回空值。

以下是该方案。

select address from sample;

将在4行后返回，

Stack Overflow# is a# question and# answer site
Stack Overflow# is a# question and# answer site
Stack Overflow# is a# question and# answer site
Stack Overflow# is a# question and# answer site

尝试使用以下查询将每行拆分为多行时，

with test as (select address as str from sample)
select regexp_substr (str, '[^#]+', 1, rownum) split
from test
connect by level <= length (regexp_substr (str, '[^#]+', 1, rownum)) + 1
;

将返回以下值。

Stack Overflow
is a
question and
answer site
(null)
(null)
(null)

为什么我无法获得所有行的结果？

Answer 1

为什么我无法获得所有行的结果？

您的查询有两件事不正确。

因为 ROWNUM 的使用不正确。您在同一查询中使用ROWNUM作为条件，但是，ROWNUM尚未递增到下一个值。所以，它的价值只有一个。所以，你只得到一行。
您需要对所有行进行拆分，而不仅仅是第一行。您需要循环遍历所有行。但是，与此同时，你应该避免循环循环并摆脱重复。

有多种方法可以为多行执行字符串拆分。我在我的文章http://lalitkumarb.wordpress.com/2015/03/04/split-comma-delimited-strings-in-a-table-using-oracle-sql/

例如，您可以这样做：

SQL> WITH t AS(
  2  SELECT 'Stack Overflow# is a# question and# answer site' text FROM dual UNION ALL
  3  SELECT 'Stack Overflow# IS a# question and# answer site' text FROM dual UNION ALL
  4  SELECT 'Stack Overflow# is a# question and# answer site' text FROM dual UNION ALL
  5  SELECT 'Stack Overflow# IS a# question and# answer site' text FROM dual
  6  )
  7  SELECT trim(regexp_substr(t.text, '[^#]+', 1, lines.column_value)) text
  8      FROM t,
  9        TABLE (CAST (MULTISET
 10        (SELECT LEVEL FROM dual CONNECT BY LEVEL <= regexp_count(t.text, '#')+1)
 11                     AS sys.odciNumberList
 12                    )
 13              ) lines
 14  /

TEXT
-----------------------------------------------
Stack Overflow
is a
question and
answer site
Stack Overflow
IS a
question and
answer site
Stack Overflow
is a
question and
answer site
Stack Overflow
IS a
question and
answer site

16 rows selected.

SQL>

所以，你现在得到 16行。效果很好！

用于根据字符将单行数据拆分为多行的SQL

1 个答案: