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• I need to auto_increment a field in MySQL that is not primary key

  - by behrk2

  Hey everyone, Right now, I have a table whose primary key is an auto_increment field. However, I need to set the primary key as username, date (to ensure that there cannot be a duplicate username with a date). I need the auto_increment field, however, in order to make changes to row information (adding and deleting). What is normally done with this situation? Thanks!

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• Better alternative to autonumber primary keys

  - by Comrad_Durandal

  I am looking for a better primary key than the autonumber data type, namely for the reason that it's limited to a long integer, when I really just need the field to reflect a number or text string that will never ever repeat, no matter HOW many records are added or deleted from the table. The problem is I am not sure how to implement something like turning the current date and time into a hexadecimal string and using that as a unique field I can use as a primary key. Am I just being too paranoid about running out of space?

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• When i should use primary key or index?

  - by Sein Kraft

  When i should use primary key or index? Which are the differences between primary key and index and which is the best?

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• Can a Compound key be set as a primary key to another table?

  - by Nikos

  Can a compound key be set as a primary key to another table? For instance i have the tables: Books -with Primary Key:Product_ID Client -with Primary key: Client_ID Clients_Books -with Compound Primary Key:Product_Id and Client_ID I want to set this compound Primary key from Clients_Books as a Primary Key to another table named: Order_Details. But I don't want to use the Product_ID and the Client_ID from the Books, Clients tables. Does this make sense? All opinions more than welcome.

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• Foreign key reference to a two-column primary key

  - by Adam Ernst

  One of my tables has a two-column primary key: CREATE TABLE tournament ( state CHAR(2) NOT NULL, year INT NOT NULL, etc..., PRIMARY KEY(state, year) ); I want a reference to the tournament table from another table, but I want this reference to be nullable. Here's how I might do it, imagining that a winner doesn't necessarily have a tournament: CREATE TABLE winner ( name VARCHAR NOT NULL, state CHAR(2) NULL, year INT NULL ); If state is null but year is not, or vice-versa, the table would be inconsistent. I believe the following FOREIGN KEY constraint fixes it: ALTER TABLE winner ADD CONSTRAINT FOREIGN KEY fk (name, state) REFERENCES tournament (name, state); Is this the proper way of enforcing consistency? Is this schema properly normalized?

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• How to update primary key

  - by slave016

  Here is my problem: I have 2 tables: 1.WORKER, with coloumns |ID|OTHER_STAF| , where ID is primary key, and 2.FIRM, with coloumns |FPK|ID|SOMETHING_ELSE| , where combination FPK and ID make primary key, and also ID is a foreign key referenced to WORKER.ID (not null, and must have same value as in WORKER). I want to make stored procedure UPDATE_ID_WORKER, where I would like to change the value of specific ID in WORKER, and also in all instances of specific value of ID in FIRM. stored procedure: ........ @id .. ???? ........ Thanks for every advice...

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• MySQL primary/foreign key size?

  - by David

  I seem to see a lot of people arbitrarily assigning large sizes to primary/foreign key fields in their MySQL schemas, such as INT(11) and even BIGINT(20) as WordPress uses. Now correct me if I'm wrong, but even an INT(4) would support (unsigned) values up to over 4 billion. Change it to INT(5) and you allow for values up to a quadrillion, which is more than you would ever need, unless possibly you're storing geodata at NASA/Google, which I'm sure most of us aren't. Is there a reason people use such large sizes for their primary keys? Seems like a waste to me...

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• Hibernate/JPA and PostgreSQL - Primary Key?

  - by Shadowman

  I'm trying to implement some basic entities using Hibernate/JPA. Initially the code was deployed on MySQL and was working fine. Now, I'm porting it over to use PostgreSQL. In MySQL, my entity class defines its primary key as an auto-incrementing long value with the following syntax: @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; However, I've found that I get errors with PostgreSQL when I try and insert numerous records at a time. What do I need to annotate my primary key with to get the same auto-incrementing behavior in PostgreSQL as I have with MySQL? Thanks for any help you can provide!

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• SQL Server Composite Primary Keys

  - by Colin

  I am attempting to replace all records for a give day in a certain table. The table has a composite primary key comprised of 7 fields. One such field is date. I have deleted all records which have a date value of 2/8/2010. When I try to then insert records into the table for 2/8/2010, I get a primary key violation. The records I am attempting to insert are only for 2/8/2010. Since date is a component of the PK, shouldn't there be no way to violate the constraint as long as the date I'm inserting is not already in the table? Thanks in advance.

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• How to get the Primary/Secondary color in jQuery UI Theme

  - by simonsanderson

  Is there a way to reference the colours used in the jQuery themes without creating a simple style for each theme that I may choose to use? Example: I have some text as follows <div>Hello</div> which I'd like to be change colour in line with my theme of the day. I wish to use the primary colour from a theme (say ui-lightness) which is "#1c94c4" as defined in several of the styles such as ui-state-default in ui-lightness.css The problem is that if I do the following <div class='ui-state-default'>Hello</div> I get all the other style effects, like borders and background colour, which are not right for my application What I'd like to do is something like <div class='ui-primary-color'>Hello</div> which would automatically change only the colour dependent on the theme. PS. Doing a pre-build pre-processing step to parse the themes and generate a customised css style would be my least favourable option here!

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• JPA - Real primary key generated ID for references

  - by Val

  I have ~10 classes, each of them, have composite key, consist of 2-4 values. 1 of the classes is a main one (let's call it "Center") and related to other as one-to-one or one-to-many. Thinking about correct way of describing this in JPA I think I need to describe all the primary keys using @Embedded / @PrimaryKey annotations. Question #1: My concern is - does it mean that on the database level I will have # of additional columns in each table referring to the "Center" equal to number of column in "Center" PK? If yes, is it possible to avoid it by using some artificial unique key for references? Could you please give an idea how real PK and the artificial one needs to be described in this case? Note: The reason why I would like to keep the real PK and not just use the unique id as PK is - my application have some data loading functionality from external data sources and sometimes they may return records which I already have in local database. If unique ID will be used as PK - for new records I won't be able to do data update, since the unique ID will not be available for just downloaded ones. At the same time it is normal case scenario for application and it just need to update of insert new records depends on if the real composite primary key matches. Question #2: All of the 10 classes have common field "date" which I described in an abstract class which each of them extends. The "date" itself is never a key, but it always a part of composite key for each class. Composite key is different for each class. To be able to use this field as a part of PK should I describe it in each class or is there any way to use it as is? I experimented with @Embedded and @PrimaryKey annotations and always got an error that eclipselink can't find field described in an abstract class. Thank you in advance! PS. I'm using latest version of eclipselink & H2 database.

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• MySQL: optimization of table (indexing, foreign key) with no primary keys

  - by Haradzieniec

  Each member has 0 or more orders. Each order contains at least 1 item. memberid - varchar, not integer - that's OK (please do not mention that's not very good, I can't change it). So, thera 3 tables: members, orders and order_items. Orders and order_items are below: CREATE TABLE `orders` ( `orderid` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT, `memberid` VARCHAR( 20 ), `Time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , `info` VARCHAR( 3200 ) NULL , PRIMARY KEY (orderid) , FOREIGN KEY (memberid) REFERENCES members(memberid) ) ENGINE = InnoDB; CREATE TABLE `order_items` ( `orderid` INT(11) UNSIGNED NOT NULL, `item_number_in_cart` tinyint(1) NOT NULL , --- 5 items in cart= 5 rows `price` DECIMAL (6,2) NOT NULL, FOREIGN KEY (orderid) REFERENCES orders(orderid) ) ENGINE = InnoDB; So, order_items table looks like: orderid - item_number_in_cart - price: ... 1000456 - 1 - 24.99 1000456 - 2 - 39.99 1000456 - 3 - 4.99 1000456 - 4 - 17.97 1000457 - 1 - 20.00 1000458 - 1 - 99.99 1000459 - 1 - 2.99 1000459 - 2 - 69.99 1000460 - 1 - 4.99 ... As you see, order_items table has no primary keys (and I think there is no sense to create an auto_increment id for this table, because once we want to extract data, we always extract it as WHERE orderid='1000456' order by item_number_in_card asc - the whole block, id woudn't be helpful in queries). Once data is inserted into order_items, it's not UPDATEd, just SELECTed. The questions are: I think it's a good idea to put index on item_number_in_cart. Could anybody please confirm that? Is there anything else I have to do with order_items to increase the performance, or that looks pretty good? I could miss something because I'm a newbie. Thank you in advance.

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• Is it OK to create all primary partitions.?

  - by james

  I have a 320GB hard disk. I only use either ubuntu or kubuntu (12.04 for now). I don't want to use windows or any other dual boot os. And i need only 3 partitions on my hard disk. One for the OS and remaining two for data storage. I don't want to create swap also. Now can i create all primary partitions on the hard disk. Are there any disadvantages in doing so. If all the partitions are primary i think i can easily resize partitions in future. On second thought i have the idea of using seperate partition for /home. Is it good practice . If i have to do this, i will create 4 partitions all primary. In any case i don't want to create more than 4 partitions . And i know the limit will be 4. So is it safe to create all 3 or 4 primary partitions. Pls suggest me, What are the good practices . (previously i used win-xp and win-7 on dual boot with 2 primary partitions and that bugged me somehow i don't remember. Since then i felt there should be only one primary partition in a hard disk.) EDIT 1 : Now i will use four partitions in the sequence - / , /home , /for-data , /swap . I have another question. Does a partition need continuous blocks on the disk. I mean if i want to resize partitions later, can i add space from sda3 to sda1. Is it possible and is it safe to do ?

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• Should foreign keys become table primary key?

  - by Carvell Fenton

  Hello again, I have a table (session_comments) with the following fields structure: student_id (foreign key to students table) session_id (foreign key to sessions table) session_subject_ID (foreign key to session_subjects table) user_id (foreign key to users table) comment_date_time comment Now, the combination of student_id, session_id, and session_subject_id will uniquely identify a comment about that student for that session subject. Given that combined they are unique, even though they are foreign keys, is there an advantage to me making them the combined primary key for that table? Thanks again.

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• How To Disable Subsonic's Primary Key Autoincrement?

  - by mamoo

  Hi everybody, I'm using Subsonic (simplerepository) and SQLite, and I have a class with an Int64 property marked as [SubSonicPrimaryKey]: [SubSonicPrimaryKey] public Int64 MyID; which is transformed into: [MyID] integer NOT NULL PRIMARY KEY AUTOINCREMENT Is it possible to disable the AUTOINCREMENT feature?

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• Datanucleus JDO Retrieve newly generated primary key

  - by DrDro

  I am using datanucleus and jdo in a GWT project. How can I retrieve the generated primary key after adding an element to the database with makePersistent()

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• Negative Primary Keys

  - by bjax

  Are there any repercussions using Negative Primary Keys for tables (Identity Increment -1, Identity Seed -1 in SQL Server 2005)? The reason for this is we're creating a new database to replace an existing one. There are similar tables between the two databases and we'd like the "source" of the information to be transparent to our applications. The approach is to create views that unions tables from both databases. Negative PKs ensures the identities don't overlap.

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• Can primary index be a CHAR in MySQL?

  - by FFish

  My primary indexes are unique reference numbers like 002345 and 000023. If I format them as integers I loose my zero's. They need to be 6 digits. Can I use CHAR? I don't need any auto increments.

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• sql swap primary key values

  - by Thomas

  Hi, is it possible to swap primary key values between two datasets? If so, how would one do that?

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• Mysql Removal of primary key

  - by marionmaiden

  Hello, I've removed the primary key of one table of my MySQL database, but now, when I use the MySQL Administrator and try to edit the data of this table, it doesn't allow me to do this. The button edit that appears in the bottom of the table keeps visible, but unable to click.

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• Android: Text primary key with different name

  - by Echilon

  I have an existing Windows app for which I'm writing an Android port. The app uses a unique string as the primary key, but the SQLite methods in Android all seem to work with integers and a column names _id, whereas my ID column isn't called this. Is there a way to let Android know I have a key with a different column name?

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• Multi-Column Primary Key in MySQL 5

  - by Kaji

  I'm trying to learn how to use keys and to break the habit of necessarily having SERIAL type IDs for all rows in all my tables. At the same time, I'm also doing many-to-many relationships, and so requiring unique values on either column of the tables that coordinate the relationships would hamper that. How can I define a primary key on a table such that any given value can be repeated in any column, so long as the combination of values across all columns is never repeated exactly?

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• Removal of table primary key in MySQL

  - by marionmaiden

  Hello, I've removed the primary key of one table of my MySQL database, but now, when I use the MySQL Administrator and try to edit some data of this table, it doesn't allow me to do this. The button edit that appears in the bottom of the table keeps visible, but disabled to click.

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• primary key datatype in sql server database

  - by ooo

  i see after installing the asp.net membership tables, they use the data type "uniqueidentifier" for all of the primary key fields. I have been using "int" data type and doing increment by one on inserts. Is there any particular benefits to using the uniqueIdentifier data type compared to my current model of using int and auto increments on new inserts ?

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• Easy mysql question regarding primary keys and an insert

  - by MPX

  In mysql, how do I get the primary key used for an insert operation, when it is autoincrementing. Basically, i want the new autoincremented value to be returned when the statement completes. Thanks!

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