3

This query:

with x as (select
'<promotions>
    <promotion promotion-id="old-promotion">
        <enabled-flag>true</enabled-flag>
        <searchable-flag>false</searchable-flag>
    </promotion>
    <promotion promotion-id="new-promotion">
        <enabled-flag>false</enabled-flag>
        <searchable-flag>false</searchable-flag>
        <exclusivity>no</exclusivity>
        <price>100</price>
        <price>200</price>
        <price>300</price>
    </promotion>
</promotions>'::xml as t
)
select 
    xpath('/promotions/promotion/@promotion-id', t) promotion_id,
    xpath('/promotions/promotion/enabled-flag/text()', t) enabled_flag,
    xpath('/promotions/promotion/exclusivity/text()', t) exclusivity,
    xpath('/promotions/promotion/price/text()', t) price
from x

for which the elements exclusivity and price do not appear in the first promotion, but do appear in the second, yields this result:

"{old-promotion,new-promotion}";"{true,false}";"{no}";"{100,200,300}"

I need to figure out how I can get a result set which will allow me to line up the exclusivity and price data to their appropriate promotion_id's. Something like this

"{old-promotion,new-promotion}";"{true,false}";"{,no}";"{,"100,200,300"}"

What do I have to do to make that happen?

4

1 回答 1

4

考虑一下：

WITH x AS (SELECT
'<promotions>
    <promotion promotion-id="old-promotion">
        <enabled-flag>true</enabled-flag>
        <searchable-flag>false</searchable-flag>
    </promotion>
    <promotion promotion-id="new-promotion">
        <enabled-flag>false</enabled-flag>
        <searchable-flag>false</searchable-flag>
        <exclusivity>no</exclusivity>
        <price>100</price>
        <price>200</price>
        <price>300</price>
    </promotion>
</promotions>'::xml AS t
)
SELECT xpath('//@promotion-id',       node) promotion_id
      ,xpath('//enabled-flag/text()', node) enabled_flag
      ,xpath('//exclusivity/text()',  node) exclusivity
      ,xpath('//price/text()',        node) price
FROM (SELECT unnest(xpath('/promotions/promotion', t)) AS node FROM x) sub

诀窍是首先在unnest().
然后从每个节点中提取属性。这样您就可以NULL自动获取缺失属性的值。

回报：

  promotion_id   | enabled_flag | exclusivity |     price
-----------------+--------------+-------------+---------------
 {old-promotion} | {true}       | {}          | {}
 {new-promotion} | {false}      | {no}        | {100,200,300}

相关问题：
XPath 查询分层数据，保留祖先-后代关系

于 2013-07-23T19:15:38.407 回答