在 Postgres 中使用 xmltable

如何解决在 Postgres 中使用 xmltable

有没有人有在 postgres 中使用 XMLTABLE 函数的经验，他们可以帮助我。我在包含 XML 数据的表中有一个文本列，我想将这些数据转换为单独的记录。数据示例如下所示。

<conditions><Condition><name>Patellar luxation</name><VeNom>19808</VeNom><PRF>False</PRF><RUWF>False</RUWF><MaintenanceCosts>1</MaintenanceCosts><ConsequentialLoss>2.5</ConsequentialLoss><GroupMCS>1</GroupMCS><GroupCLS>2.5</GroupCLS><score>2.5</score><id>125</id><GroupId>1</GroupId><Groupscore>2.5</Groupscore><exclusionType>None</exclusionType><questions><QandA><question>Has your pet had an operation for this condition?</question><answer>No</answer></QandA><QandA><question>Does your pet have any other bone or joint problems?</question><answer>No</answer></QandA><QandA><question>Has the vet ever recommended that your pet lose weight?</question><answer>No</answer></QandA></questions><LinkedConditions><LinkedCondition Name="Complications with the other patellar / knee" VeNom="" Type="D"/><LinkedCondition Name="Cruciate ligament disease" VeNom="" Type="D"/></LinkedConditions></Condition></conditions>

我想将 QandA 分成这样的单个记录：-

Question                                  Answer
---------                                 -------
Has your pet ....                         No
Does your pet have any other bone ...     No
Has the vet ever recommended ...          No

阅读了一些关于此的在线资料后，我想出了这个 sql，但收到一个错误

with data as
(
select questionsandanswers::xml as qa
from mytable
)
SELECT *
    FROM   data x,XMLTABLE('conditions/Condition/questions/QandA'
              PASSING qa
              COLUMNS 
                q     text  PATH 'question',a     text  PATH 'answer' )

ERROR:  Could not parse XML document
DETAIL:  line 1: Document is empty

^
sql state: 2200M

任何帮助将不胜感激。我使用的是 Postgresql V 11.9

解决方法

你的代码看起来是正确的，如果你直接在字符串上尝试

with data as (
select '<conditions><Condition><name>Patellar luxation</name><VeNom>19808</VeNom><PRF>False</PRF><RUWF>False</RUWF><MaintenanceCosts>1</MaintenanceCosts><ConsequentialLoss>2.5</ConsequentialLoss><GroupMCS>1</GroupMCS><GroupCLS>2.5</GroupCLS><Score>2.5</Score><id>125</id><GroupId>1</GroupId><GroupScore>2.5</GroupScore><exclusionType>None</exclusionType><questions><QandA><question>Has your pet had an operation for this condition?</question><answer>No</answer></QandA><QandA><question>Does your pet have any other bone or joint problems?</question><answer>No</answer></QandA><QandA><question>Has the vet ever recommended that your pet lose weight?</question><answer>No</answer></QandA></questions><LinkedConditions><LinkedCondition Name="Complications with the other patellar / knee" VeNom="" Type="D"/><LinkedCondition Name="Cruciate ligament disease" VeNom="" Type="D"/></LinkedConditions></Condition></conditions>'::xml val)
 SELECT q,a
    FROM   data x,XMLTABLE('conditions/Condition/questions/QandA'
              PASSING val
              COLUMNS 
                q     text  PATH 'question',a     text  PATH 'answer' )
;

提供预期的输出

                            q                            | a  
---------------------------------------------------------+----
 Has your pet had an operation for this condition?       | No
 Does your pet have any other bone or joint problems?    | No
 Has the vet ever recommended that your pet lose weight? | No
(3 rows)

但是，如果针对如下所示的空字符串运行相同的代码

with data as (
select ''::xml val)
 SELECT q,a     text  PATH 'answer' )
;

它抛出你提到的错误

ERROR:  could not parse XML document
DETAIL:  line 1: Document is empty

您应该更多地关注理解/消除带有空 XML 字符串的行的连接

好的，看来我的语法是正确的，但我的文件中有一些空数据问答栏目。全部整理完毕