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MySQL/InnoDB: more optimal to have two non-unique index columns or combine them in unique primary key?
by DesiPower in Databases

I'm using MySQL with InnoDB.


I don't need a primary key in terms of semantics, so does a primary key (or rather, a unique index) make for faster queries than a non-unique index?


I have two columns that are suitable for indexes but are non-unique. However, combinations of the two columns are always unique. The columns are also non-null.


Is it better to just se


Convincing the Oracle SQL optimizer that an indexed (though non-UNIQUE) column actually contains unique values in practice
by socurious in Programming Languages

I am writing a view that uses a column with a non-UNIQUE index on it. However, within the context of my view, I am confident that the column will only contain unique values (due to the conditions imposed in the WHERE clause).


The real problem happens when someone queries the view based on that column (e.g. SELECT * FROM MY_VIEW WHERE COLUMN_WITH_NON_U


Generating Order Numbers - Keep unique across multiple machines - Unique string seed
by Navin in Web Design

I'm attempting to create an order number for customers to use. I will have multiple machines that do not have access to the same database (so can't use primary keys and generate a unique ID).


I will have a unique string that I could use for a seed for some algorithm that will generate a unique looking alphanumeric ID # for the order number. I do not want to use this unique strin


How to match unique ID from the different table in database and retrieve data according to that unique ID in Java?
by jasonmoo in Java

Table user in database(postgresql) has unique id for each user, dob, first and last names of the user;
Table points in database has userID and gamePoints columns.


In java servlet, how do I match and retrieve who exactly that user is with points and output? Fuzzy Match??


example:


Table user:
userID-name-lastname-dob
1-Edward-Maka-1950
2-

Hibernate throws unique constraint violation exception while updating field part of unique key
by hovergirl in Programming Languages

Below is the use case:
I have a unique index defined on 3 columns say A,B,C. Assume the values in them are A1,B1,C1.
My java code is adding a new record say A1,B1,C1 but before this record is added, i update the previous value from C1 to C2. While trying to add the new record (after the update), hibernate is throwing an unique constraint violation exception. Any reason as to why it do


How i can force the entity framework to raise a unique exception if the Unique key constraint has been violated on thr sql server database
by Minh Nguyen in Programming Languages

I have a table named countries and i define the country_name field to be unique by creating a “Index/Key” of type “Unique Key” on sql servwer 2008 r2.
But currently if the user insert a country_name value that already exists on my asp.net mvc3 application, then an exception of type “System.Data.Entity.Infrastructure.DbUpdateException” will be raised , which is very general.


Is the Window handle revealed by Spy++ unique to that computer, or unique to the application
by IeraseU in Programming Languages

Ok, so I have a Microsoft Access form which contains a textbox which I am trying to get a handle on from .Net


My form is below:



Using Spy++, I have found my textbox handle. A screenshow is below:



Is this handle unique to my PC or frmTest? As in, if I open frmTest on another computer will the handle for my textbox still be 001E1A6E?


is there a .NET C# collection that supports fetch by both unique keys and non-unique fields?
by cakephp in C & C++ & C#

My need is to have items in kind of Collections.Generic.Dictionary where I can get a struct by it's id as a key. Then I have need to fetch many structs, say 1% or less of all items, by another field. Like a cursor by an non-unique index. With Dictionary I have to browse through all the values and check which has the correct value for that field. My question is: "What data structure should I use


Making a unique attribute in an already existing table NOT unique - MYSQL
by Matthew Steed in Databases

A non-unique attribute of a table can be made unique by the query:


ALTER TABLE mytbl ADD UNIQUE (columnName);

I need to set a already unique attribute of a table NON-unique. Can anyone help me with the query?


How to do a MySQL Insert if unique, but the columns are too long for unique index
by IlLogiK in Databases

I have found a great answer for when inserting a new record, ignore if the data already exists.


1) Create a UNIQUE INDEX on the columns.


2) INSERT IGNORE INTO ...


But my problem is that one of the columns is a VARCHAR(2000)**, and MySQL has a 1000-character limit to indexes.


The columns are: id (int), type (varchar 35), data (varchar 2000)



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