DQL - DOCUMENTUM QUERY LANGUAGE
Just to start with, I want to give a brief introduction of DQL which will give a basic idea about DQL, its purpose, how it works and tools used (w.r.t Documentum 5.x) and also the major enhancements on DQL in Documentum 6.x.
Introduction to DQL
DQL - Documentum Query Language
DQL is used to query Documentum which is a content management system used to create, manage, deliver, and archive all types of content from text documents and spreadsheets to digital images, HTML, and XML components.
Difference between DQL & SQL
DQL uses syntax that is a superset of ANSI-standard SQL (Structured Query Language) DQL statements operate on objects and sometimes on tables/rows but SQL statements operate only on tables/rows
In fact, part of your DQL statements are translated automatically into SQL before being executed by the eContent Server
DQL (Documentum Query Language) is a query language which allows you to do very complex queries involving:
1. Property searches
2. Searches for words and phrases within documents
3. Other specialized searching capabilities added for document and content management
How it works?
A DQL query is sent to the eContent Server using one of four API methods (readquery, execquery, query, or cachequery)
A DQL engine on eContent Server generates
– SQL queries for the RDBMS
– Verity queries for the full-text search engine
The results of the query are stored on the server in a non-persistent collection object. Typically, a Documentum client will automatically present the results of the query to the user in some useful way. Alternatively, a Developer may want to use the resulting collection object or manipulate the results programmatically.
Provisions for Query Execution:
DQL queries can be executed via:
1. IDQL Utility - Interactive DQL Utility - On the Content Server host you can find the executable idql32.exe on Windows machines
2. Web clients such as Documentum Administrator or Web Publisher
What's New in Documentum 6.x?
In Documentum 6.x, the changes effected by DQL - CREATE OBJECT, DELETE OBJECT and UPDATE OBJECT - are made BOF-aware, although CREATE GROUP, ALTER GROUP, and DROP GROUP are not affected by this change
We will see more about DQL in the fore coming articles, how to form a query using DQL, and reserved keywords in DQL and basic and advanced queries using DQL.
Also we will see the advantages and limitations of using DQL as well as API and the comparison between them as well in the next article.