Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com
Answertopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 

14.18. Row value constructor syntax

HQL supports the use of ANSI SQL row value constructor syntax (sometimes called tuple syntax), even though the underlying database may not support that notion. Here we are generally referring to multi-valued comparisons, typically associated with components. Consider an entity Person which defines a name component:
from Person p where p.name.first='John' and p.name.last='Jingleheimer-Schmidt'
That's valid syntax, although a little verbose. It be nice to make this a bit more concise and use row value constructor syntax:
from Person p where p.name=('John', 'Jingleheimer-Schmidt')
It can also be useful to specify this in the select clause:
select p.name from from Person p
Another time using row value constructor syntax can be beneficial is when using subqueries needing to compare against multiple values:
from Cat as cat
where not ( cat.name, cat.color ) in (
    select cat.name, cat.color from DomesticCat cat
)
One thing to consider when deciding if you want to use this syntax is that the query will be dependent upon the ordering of the component sub-properties in the metadata.

 
 
  Published under the terms of the Open Publication License Design by Interspire