[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2434) No standard way to calculate date intervals in HQL

No standard way to calculate date intervals in HQL -------------------------------------------------- Key: HHH-2434 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2434 Project: Hibernate3 Type: Improvement

Components: core Versions: 3.2.0.ga Environment: All Reporter: Don Smith Priority: Minor

Date interval calculation is supported differently on different database platforms. Some allow direct arithmetic on columns, i.e. enddate - startdate. Some require functions, datediff(), timestampdiff(), etc. This causes cross-platform issues. For instance, an application I work on has to figure out the dialect that's in use (out of the four we currently support) and create the HQL string differently for each platform. This is undesirable, since we use Hibernate to enable platform neutrality; our installer asks which database the customer wants to deploy to, and sets the dialect. We'd like our codebase to be free of dialect-specific code. I propose a standard solution for this, either direct date arithmetic, or a function defintion that is ported across dialects. Timestampdiff seems to be a fairly standard function, although DB2 has different syntax than MySQL and Derby. I've seen hints that timestampdiff is part of the ANSI SQL standard, but do not have access to the documents to determine if that is the case.