Hi,
(DB2 LUW 8.2)
Is the DB2 optimiser able to use check constraints ?
e.g
table1
(
name varchar(30)
constraint c_upper check (name = UCASE(name))
)
CREATE INDEX table1_ix1 ON table1 (name ASC) ALLOW REVERSE SCANS;
would a query like
select * from table1 where ucase(name) = 'PAUL'
recognise that the index table1_ix1 was valid to be considered to be
used?
nb. at the moment we use indexed generated columns to achieve this.
1  1603 
PaulR wrote:
Hi,
(DB2 LUW 8.2)
Is the DB2 optimiser able to use check constraints ?
e.g
table1
(
name varchar(30)
constraint c_upper check (name = UCASE(name))
)
CREATE INDEX table1_ix1 ON table1 (name ASC) ALLOW REVERSE SCANS;
would a query like
select * from table1 where ucase(name) = 'PAUL'
recognise that the index table1_ix1 was valid to be considered to be
used?
nb. at the moment we use indexed generated columns to achieve this.
The optimizer can use check constraints in some circumstances, such as
a UNION ALL view, but I don't think it would work in your example. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
by: hemal |
last post by:
I came across a very strange situation at work. There is an order of
magnitude difference in execution time for the following two queries
(10 v/s ~130 msec):
select count(*) from table_name where column_name = 'value' or 1 = 0
select count(*) from table_name where column_name = 'value'
I do not want to go into the reason why the redundent condition
exists, the example is representative of the real query where it
|
by: Ian Ribas |
last post by:
Hello,
This is probably a common problem, but I couldn't really find a direct answer in
the archives (or maybe just couldn't find one that satisfied me ;-). I created
an index specifically to help a query and the optimizer does not use it. It
prefers an older index that has one less column, but that yields much poorer
performance.
The query get the smallest date in a period, for some criteria. The one table
used in the query has...
|
by: Ian Ribas |
last post by:
Hello,
This is probably a common problem, but I couldn't really find a direct answer in
the archives (or maybe just couldn't find one that satisfied me ;-). I created
an index specifically to help a query and the optimizer does not use it. It
prefers an older index that has one less column, but that yields much poorer
performance.
The query get the smallest date in a period, for some criteria. The one table
used in the query has...
|
by: ferg |
last post by:
I have a Customer table. The table has two different CHECK constraints.
Then there is the Customer details dialog, which provides the user with
an UI for changing users. I have some UPDATE sql, which is called once
the user clicks the OK button on this dialog.
try
{
int rows = cmd.ExecuteNonQuery();
}
catch(SqlException se)
|
by: marktang |
last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look !
Part I. Meaning of...
| | |
by: Oralloy |
last post by:
Hello folks,
I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>".
The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed.
This is as boiled down as I can make it.
Here is my compilation command:
g++-12 -std=c++20 -Wnarrowing bit_field.cpp
Here is the code in...
|
by: Hystou |
last post by:
Overview:
Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
|
by: tracyyun |
last post by:
Dear forum friends,
With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own....
Now, this would greatly impact the work of software developers. The idea...
|
by: isladogs |
last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM).
In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules.
He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms.
Adolph will...
|
by: conductexam |
last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one.
At the time of converting from word file to html my equations which are in the word document file was convert into image.
Globals.ThisAddIn.Application.ActiveDocument.Select();...
| | |
by: TSSRALBI |
last post by:
Hello
I'm a network technician in training and I need your help.
I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs.
The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols.
I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
|
by: bsmnconsultancy |
last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...
| |
