Author: tfischer
Date: Sun Oct 8 02:44:40 2006
New Revision: 454111
URL: http://svn.apache.org/viewvc?view=rev&rev=454111
Log:
Added a section about Oracle's treatment of empty strings.
Thanks to Parthasarathy Thandavarayan for reporting the problem and to Thoralf
Rickert to provide a workaround.
Modified:
db/torque/site/trunk/xdocs/version-specific/database-howtos/oracle-howto.xml
Modified:
db/torque/site/trunk/xdocs/version-specific/database-howtos/oracle-howto.xml
URL:
http://svn.apache.org/viewvc/db/torque/site/trunk/xdocs/version-specific/database-howtos/oracle-howto.xml?view=diff&rev=454111&r1=454110&r2=454111
==============================================================================
---
db/torque/site/trunk/xdocs/version-specific/database-howtos/oracle-howto.xml
(original)
+++
db/torque/site/trunk/xdocs/version-specific/database-howtos/oracle-howto.xml
Sun Oct 8 02:44:40 2006
@@ -48,6 +48,25 @@
instead which gives you millisecond accuracy.
</p>
+ <p>
+ Oracle does not distinguish between empty strings and null strings.
+ If an empty string is inserted into a table, it will be treated as null.
+ If you want to re-read this column by selecting records which contain
+ an empty string, oracle will return no columns. The only way to select
+ the column is to query for records which contain null in that column.
+ <br/>
+ This behaviour is different in most other databases. So if you
+ want to write code which works for other databases and oracle, you need
+ to consider both cases - the column might be null and it might contain
+ an empty string. For example:
+ </p>
+
+<source>
+Criteria.Criterion c1 = criteria.getNewCriterion(COLUMN, "", Criteria.EQUAL);
+Criteria.Criterion c2 = criteria.getNewCriterion(COLUMN, (Object)null,
Criteria.ISNULL);
+criteria.add(c1.or(c2));
+</source>
+
<subsection name="Oracle versions">
<p>
This version of Torque is optimized for Oracle 9i and later.
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