Question

I have an large list of XML documents stored in MySQL (yes I know…) and I’m wondering if there is an easy way to do a search and replace on the documents using just SQL.

In the example below, I’m trying to replace mandown (both the value & the element) with emergkey.

Original:

<clouddata>
 <type>mandown</type>
 <devicedata>
  <nomotion>0</nomotion>
  <mandown>1</mandown>
 </devicedata>
</clouddata>

Desired:

<clouddata>
 <type>emergkey</type>
 <devicedata>
  <nomotion>0</nomotion>
  <emergykey>1</emergkey>
 </devicedata>
</clouddata>

Note that I’ve simplified these examples and the real data is of various length and the elements are not necessarily ordered all the same.

Answer 1

The brain-dead method is

UPDATE yourtable SET xmlfield=REPLACE(xmlfield, 'mandown', 'emergykey');

or in slightly safer fashion:

UPDATE yourtable SET xmlfield=REPLACE(xmlfield, '<mandown>', '<emergykey>');
UPDATE yourtable SET xmlfield=REPLACE(xmlfield, '</mandown>', '</emergykey>');
UPDATE yourtable SET xmlfield=REPLACE(xmlfield, '<type>mandown</type>', '<type>emergykey</type>');

A truly safe method would be to pull each record into DOM and do the operations there, though this’d be slow on a large table.