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  • How to explain to users the advantages of dumb primary key?

    - by Hao
    Primary key attractiveness I have a boss(and also users) that wants primary key to be sophisticated/smart/attractive control number(sort of like Social Security number, or credit card number format) I just padded the primary key(in Views) with zeroes to appease their desire to make the control number sophisticated,smart and attractive. But they wanted it as: first 2 digits as client code, then 4 digits as year year, then last 4 digits as transaction number on that client on a given year, then reset the transaction number of client to 1 when next year flows. Each client's transaction starts with 1. e.g. WM20090001, WM20090002, BB2009001, WM20100001, BB20100001 But as I wanted to make things as simple as possible, I forgo embedding their suggested smartness in primary key, I just keep the primary key auto increments regardless of client and year. But to make it not dull-looking(they really are adamant to make the primary key as smart control number), I made the primary key appears to them smart, on view query, I put the client code and four digit year code on front of the eight-zero padded autoincrement key, i.e. WM200900000001. Sort of slug-like information on autoincremented primary key. Keeping primary key autoincrement regardless of any other information, we are able keep other potential side effects problem when they edit a record, for example, if they made a mistake of entering the transaction on WM, then they edit the client code to BB, if we use smart primary key, the primary keys of WM customer will have gaps in their control number. Or worse yet, instead of letting the control numbers have gaps/holes, the user will request that subsequent records of that gap should shift up to that gap and have their subsequent primary keys re-adjust(decremented). How do you deal with these user requests(reasonable or otherwise)? Do you yield to their request? Or just continue using dumb primary key and explain them the repercussions of having a very smart/sophisticated primary key and educate them the significant advantages of having a dumb primary key? P.S. quotable quote(http://articles.techrepublic.com.com/5100-10878_11-1044961.html): "If you hold your tongue the first time users ask what is for them a reasonable request, things will work a lot better in the end."

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  • I accidentally made my new hard drive (the non system drive) my primary partition

    - by qwerty2
    Hi all, When installing a new hard drive, I accidentally formatted it using 'Disk Management' and set it up as my primary active partition, even though it isn't the system drive. Then, when I restarted my machine, Windows wouldn't boot, citing a missing or corrupt SYSTEM folder. Can anyone help me re-enable the system hard drive as my primary active partition? Any help would be greatly appreciated.

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  • How to change partitioning - may involve conversion of a partition from primary to extended

    - by george_k
    I am having trouble thinking through how I can achieve my partitioning goals. Now my partitions are: sda1 (winA) (primary) sda2 (winB) (primary) sda3 (/ for ubuntu) (primary) What I want to migrate into is (obviously partition numbers need not be exactly like that) sda1 (winA) (primary) sda2 (winB) (primary) sda3 (/boot) (primary) sda4 - extended which will contain sda5 (/home) sda6 (/ for ubuntu) sda7 (swap) I know I may be asking too much, but what would a way to do it? One way I have thought is Create a new primary partition for /boot and split it from the root partition into the new one. It shouldn't be too hard. Then the disk will have 4 primary partitions. Somehow convert the root ubuntu partition from primary to extended. Split that last partition in 3 extended partitions (root, /home, swap) and split the contents there. I am obviously stuck on the 2nd part. Another way could be (maybe easier): Create an extended partition (or two) Split /home there Somehow move everything except /boot to the extended partition. This way /boot will stay on the primary partition that exists now, and will be shrunk as needed, and everything else will end up to the extended partitions. This may sound better, but I'm not too sure how to do the 3rd part. Some details: The disk is almost empty, so I have space to move things around in it, shrink the ubuntu partition etc. I don't want to touch the windows partitions in any way. Reinstallation is not an option. Also using a different partitioning scheme with fewer partitions is not an option (for example not having a separate /boot) Any ideas?

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  • Using datetime float representation as primary key

    - by devanalyst
    From my experience I have learn that using an surrogate INT data type column as primary key esp. an IDENTITY key column offers better performance than using GUID or char/varchar data type column as primary key. I try to use IDENTITY key as primary key wherever possible. But recently I came across a schema where the tables were horizontally partitioned and were managed via a Partitioned view. So the tables could not have an IDENTITY column since that would make the Partitioned View non updatable. One work around for this was to create a dummy 'keygenerator' table with an identity column to generate IDs for primary key. But this would mean having a 'keygenerator' table for each of the Partitioned View. My next thought was to use float as a primary key. The reason is the following key algorithm that I devised DECLARE @KEY FLOAT SET @KEY = CONVERT(FLOAT,GETDATE())/100000.0 SET @KEY = @EMP_ID + @KEY Heres how it works. CONVERT(FLOAT,GETDATE()) gives float representation of current datetime since internally all datetime are represented by SQL as a float value. CONVERT(FLOAT,GETDATE())/100000.0 converts the float representation into complete decimal value i.e. all digits are pushed to right side of ".". @KEY = @EMP_ID + @KEY adds the Employee ID which is an integer to this decimal value. The logic is that the Employee ID is guaranteed to be unique across sessions since an employee cannot connect to an application more than once at the same time. And for the same employee each time a key will be generated the current datetime will be unique. In all an unique key across all employee sessions and across time. So for Emp Ids 11 and 12, I have key values like 12.40046693321566357, 11.40046693542361111 But my concern whether float data type as primary key offer benefits compared to choosing GUID or char/varchar as primary keys. Also important thing is because of partitioning the float column is going to be part of a composite key.

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  • Multiple Columns as Primary keys

    - by rockbala
    CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName) ) The above example is taken from w3schools. From the above example, my understanding is that both P_Id, LastName together represents a Primary Key for the table Persons, correct ? Another question is why would some one want to use multiple columns as Primary keys instead of a single column ? How many such columns can be used in together as Primary key in a given table ? Thanks Balaji S

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  • Use Case Actors - Primary versus Secondary

    - by Dave Burke
    The Unified Modeling Language (UML1) defines an Actor (from UseCases) as: An actor specifies a role played by a user or any other system that interacts with the subject. In Alistair Cockburn’s book “Writing Effective Use Cases” (2) Actors are further defined as follows: Primary Actor: The primary actor of a use case is the stakeholder that calls on the system to deliver one of its services. It has a goal with respect to the system – one that can be satisfied by its operation. The primary actor is often, but not always, the actor who triggers the use case. Supporting Actors: A supporting actor in a use case in an external actor that provides a service to the system under design. It might be a high-speed printer, a web service, or humans that have to do some research and get back to us. In a 2006 article (3) Cockburn refined the definitions slightly to read: Primary Actors: The Actor(s) using the system to achieve a goal. The Use Case documents the interactions between the system and the actors to achieve the goal of the primary actor. Secondary Actors: Actors that the system needs assistance from to achieve the primary actor’s goal. Finally, the Oracle Unified Method (OUM) concurs with the UML definition of Actors, along with Cockburn’s refinement, but OUM also includes the following: Secondary actors may or may not have goals that they expect to be satisfied by the use case, the primary actor always has a goal, and the use case exists to satisfy the primary actor. Now that we are on the same “page”, let’s consider two examples: A bank loan officer wants to review a loan application from a customer, and part of the process involves a real-time credit rating check. Use Case Name: Review Loan Application Primary Actor: Loan Officer Secondary Actors: Credit Rating System A Human Resources manager wants to change the job code of an employee, and as part of the process, automatically notify several other departments within the company of the change. Use Case Name: Maintain Job Code Primary Actor: Human Resources Manager Secondary Actors: None The first example is quite straight forward; we need to define the Secondary Actor because without the “Credit Rating System” we cannot successfully complete the Use Case. In other words, the goal of the Primary Actor is to successfully complete the Loan Application, but they need the explicit “help” of the Secondary Actor (Credit Rating System) to achieve this goal. The second example is where people sometimes get confused. Within OUM we would not include the “other departments” as Secondary Actors and therefore not include them on the Use Case diagram for the following reasons: The other departments are not required for the successful completion of the Use Case We are not expecting any response from the other departments (at least within the bounds of the Use Case under discussion) Having said that, within the detail of the Use Case Specification Main Success Scenario, we would include something like: “The system sends a notification to the related department heads (ref. Business Rule BR101)” Now let’s consider one final example. A Procurement Manager wants to place a “bid” for some goods using an On-Line Trading Community (B2B version of eBay) Use Case Name: Create Bid Primary Actor: Procurement Manager Secondary Actors: On-Line Trading Community You might wonder why the Trading Community is listed as a Secondary Actor, i.e. if all we are going to do is place a bid for a specific quantity of goods at a given price and send that off to the Trading Community, then why would the Trading Community need to “assist” in that Use Case? Well, once again, it comes back to the “User Experience” and how we want to optimize that when we think about our Use Case, and ultimately, when the developer comes to assembling some code. In this final example, the Procurement Manager cannot successfully complete the “Create Bid” Use Case until they receive an affirmative confirmation back from the Trading Community that the Bid has been accepted. Therefore, the Trading Community must become a Secondary Actor and be referenced both on the Use Case diagram and Use Case Specification. Any astute readers who are wondering about the “single sitting” rule will have to wait for a follow-up Blog entry to find out how that consideration can be factored in!!! Happy Use Case writing! (1) OMG Unified Modeling LanguageTM (OMG UML), Superstructure Version 2.4.1 (2) Cockburn, A, 2000, Writing Effective Use Case, Addison-Wesley Professional; Edition 1 (3) Cockburn, A, 2006 “Use Case fundamentals” viewed 20th March 2012, http://alistair.cockburn.us/Use+case+fundamentals

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  • How Can I Reference Multiple Primary Keys For A Vector Type Primary Key

    - by AndreiC
    Hi, I have the following scenario: a table of projects and a table of persons, working on one or serveral projects. Also, I have a project id column (of type int), in the first table, which is a primary key there and I have a vector of project ids, as a column of type int, in my second table (persons), that references primary keys from the first table. What is the correct syntax for referencing multiple primary keys, from a vector foreign key. This is the way I am trying to create the table, but I am not sure what to place at the indicated line: CREATE TABLE Persons( Person_Id int, ..., ProjectsList int[], FOREIGN KEY (ProjectsList) REFERENCES Projects(Project_id) -- not sure what how to define the link here ); I hope my explanations are not over-complicated. Thank you in advance for helping!

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  • SQL Server add primary key

    - by Paul
    I have a table that needs to be given a new primary key, as my predecesor used a varchar(8) row as the primary key, and we are having problems with it now. I know how to add the primary key, but am not sure of the correct way to add this new primary key to other tables that have the foreign key. Here is what I have: users table: old_user_id varchar(8) ... ... new_user_id int(11) orders table: order_id int(11) ... ... old_user_fk varchar(8) new_user_fk int(11) I need to get the same results whether I join the tables on users.old_user_id=orders.old_user_fk or users.new_user_id=orders.new_user_fk. Any help is appreciated.

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  • DB Designer creates compound primary key

    - by Jon Winstanley
    When adding relationships to a database model in DB Designer 4, a composite primary key is being created every time. So every foreign key I add, I get an extra key added to a composite primary key. I think I must have changed a setting as I don't remember it doing this in the past. Does anyone know how to turn off this feature as I prefer to use a single surrogate primary keys in my database tables?

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  • Change an access Primary key with relationships

    - by DiegoMaK
    I have a database in access 2007 accdb extension , there are more or less 30-40 tables with related primary key "local_number". it is a text primary key with 10 lenght. How can I change the length of this primary key to 30 WITHOUT delete previosly all the 30 relationship. 2,A similar question. I need add a compose primary key to my PK "local_number". I need Add a "Date" as composed PK. Then access just allow this if I first delete all relationships. How can Avoid this warning and change my PK ignoring this message.

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  • SQL multiple primary keys - localization

    - by Max Malmgren
    I am trying to implement some localization in my database. It looks something like this (prefixes only for clarification) tbl-Categories ID Language Name tbl-Articles ID CategoryID Now, in my tbl-Categories, I want to have primary keys spanning ID and language, so that every combination of ID and language is unique. In tbl-Articles I would like a foreign key to reference ID in categories, but not Language, since I do not want to bind an article to a certain language, only category. Of course, I cannot add a foreign key to part of the primary key. I also cannot have the primary key only on the ID of categories, since then there can only be one language. Having no primary keys disables foreign keys altogether, and that is also not a great solution. Do you have any ideas how I can solve this in an elegant fashion? Thanks.

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  • Meaning of Primary Key to Microsoft SQL Server 2008

    - by usr
    What meaning does the concept of a primary key have to the database engine of SQL Server? I don't mean the clustered/nonclustered index created on the "ID" column, i mean the constraint object "primary key". Does it matter if it exists or not? Alternatives: alter table add primary key clustered alter table create clustered index Does it make a difference?

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  • Indexes and multi column primary keys

    - by David Jenings
    Went searching and didn't find the answer to this specific noob question. My apologies if I missed it. In a MySQL database I have a table with the following primary key PRIMARY KEY id (invoice, item) In my application I will also frequently be selecting on "item" by itself and less frequently on only "invoice". I'm assuming I would benefit from indexes on these columns. MySQL does not complain when I define the following: INDEX (invoice), INDEX (item), PRIMARY KEY id (invoice, item) But I don't see any evidence (using DESCRIBE -- the only way I know how to look) that separate indexes have been established for these two columns. So the question is, are the columns that make up a primary key automatically indexed individually? Also, is there a better way than DESCRIBE to explore the structure of my table?

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  • How can I make Access think there is a primary key

    - by user3692757
    I have a table and I'm trying to join it with another table, but it doesn't have a distinctive primary key. The two tables do share similarities, “Acct” and “Location”. If I could concatenate “Acct&Location” it would become a primary key, but Access won’t let me make a primary key from a calculation. I provided a small sample below. Each hospital has an “Acct”, but the “Acct” will show up once for each “Location”. How can I make join these in a relationship? I connected the two in a relationships and tried to “Enforce Referential Integrity”, but it indicated “No unique index found for the referenced field of the primary key”. Also, if I run a “Find UnMatched Query” it doesn’t find anything. I think its because I can’t make it realize that in combination “Acct” and “Location” can be perceived as primary keys when used in conjunction of each other. Acct 1 2 3 1 2 3 1 2 3| Location ABI ABI ABI NHO NHO NHO NTX NTX NTX I tried to load an image to illustrate it better, but I haven't made enough post.

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  • referencing part of the composite primary key

    - by Zavael
    I have problems with setting the reference on database table. I have following structure: CREATE TABLE club( id INTEGER NOT NULL, name_short VARCHAR(30), name_full VARCHAR(70) NOT NULL ); CREATE UNIQUE INDEX club_uix ON club(id); ALTER TABLE club ADD CONSTRAINT club_pk PRIMARY KEY (id); CREATE TABLE team( id INTEGER NOT NULL, club_id INTEGER NOT NULL, team_name VARCHAR(30) ); CREATE UNIQUE INDEX team_uix ON team(id, club_id); ALTER TABLE team ADD CONSTRAINT team_pk PRIMARY KEY (id, club_id); ALTER TABLE team ADD FOREIGN KEY (club_id) REFERENCES club(id); CREATE TABLE person( id INTEGER NOT NULL, first_name VARCHAR(20), last_name VARCHAR(20) NOT NULL ); CREATE UNIQUE INDEX person_uix ON person(id); ALTER TABLE person ADD PRIMARY KEY (id); CREATE TABLE contract( person_id INTEGER NOT NULL, club_id INTEGER NOT NULL, wage INTEGER ); CREATE UNIQUE INDEX contract_uix on contract(person_id); ALTER TABLE contract ADD CONSTRAINT contract_pk PRIMARY KEY (person_id); ALTER TABLE contract ADD FOREIGN KEY (club_id) REFERENCES club(id); ALTER TABLE contract ADD FOREIGN KEY (person_id) REFERENCES person(id); CREATE TABLE player( person_id INTEGER NOT NULL, team_id INTEGER, height SMALLINT, weight SMALLINT ); CREATE UNIQUE INDEX player_uix on player(person_id); ALTER TABLE player ADD CONSTRAINT player_pk PRIMARY KEY (person_id); ALTER TABLE player ADD FOREIGN KEY (person_id) REFERENCES person(id); -- ALTER TABLE player ADD FOREIGN KEY (team_id) REFERENCES team(id); --this is not working It gives me this error: Error code -5529, SQL state 42529: a UNIQUE constraint does not exist on referenced columns: TEAM in statement [ALTER TABLE player ADD FOREIGN KEY (team_id) REFERENCES team(id)] As you can see, team table has composite primary key (club_id + id), the person references club through contract. Person has some common attributes for player and other staff types. One club can have multiple teams. Employed person has to have a contract with a club. Player (is the specification of person) - if emplyed - can be assigned to one of the club's teams. Is there better way to design my structure? I thought about excluding the club_id from team's primary key, but I would like to know if this is the only way. Thanks. UPDATE 1 I would like to have the id as team identification only within the club, so multiple teams can have equal id as long as they belong to different clubs. Is it possible? UPDATE 2 updated the naming convention as adviced by philip Some business rules to better understand the structure: One club can have 1..n teams (Main squad, Reserve squad, Youth squad or Team A, Team B... only team can play match, not club) One team belongs to one club only A player is type of person (other types (staff) are scouts, coaches etc so they do not need to belong to specific team, just to the club, if employed) Person can have 0..1 contract with 1 club (that means he is employed or unemployed) Player (if employed) belongs to one team of the club Now thinking about it - moving team_id from player to contract would solve my problem, and it could hold the condition "Player (if employed) belongs to one team of the club", but it would be redundant for other staff types. What do you think?

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  • Should a primary key be immutable?

    - by Vincent Malgrat
    A recent question on stackoverflow provoked a discussion about the immutability of primary keys. I had thought that it was a kind of rule that primary keys should be immutable. If there is a chance that some day a primary key would be updated, I thought you should use a surrogate key. However it is not in the SQL standard and some RDBMS' "cascade update" feature allows a primary key to change. So my question is: is it still a bad practice to have a primary key that may change ? What are the cons, if any, of having a mutable primary key ?

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  • Should I obscure primary key values?

    - by Scott
    I'm building a web application where the front end is a highly-specialized search engine. Searching is handled at the main URL, and the user is passed off to a sub-directory when they click on a search result for a more detailed display. This hand-off is being done as a GET request with the primary key being passed in the query string. I seem to recall reading somewhere that exposing primary keys to the user was not a good idea, so I decided to implement reversible encryption. I'm starting to wonder if I'm just being paranoid. The reversible encryption (base64) is probably easily broken by anybody who cares to try, makes the URLs very ugly, and also longer than they otherwise would be. Should I just drop the encryption and send my primary keys in the clear?

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  • Choice of primary index for mysql innoDB

    - by Saif Bechan
    I have an auction website where users can place a bid on a product. Now i have a primary index on the bid table for easy access of the last places bid on the product. This index is just a unique auto incrementing value. During the week this number becomes huge!! I was wondering if this is a good setup for the primary key in an innoDB table. The bids table exist of the following important fields: table: bids fields: user_id,product_id,bid So what i want to do is make the primary of these 3 fields combined. Is this a good idea or is this just too much for innoDB keys.

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  • add ANOTHER primary key to a table which is UNIQUE

    - by gdubs
    so im having problems with adding another primary key to my table. i have 3 columns: 1. Account ID (Identity) 2. EmailID 3. Data field when i made the table i had this to make the Account ID and the Email ID unique PRIMARY KEY (AccountID, EmailID) i thought that would make my emailid unique, but then after i tried inserting another row with the same emailid it went through. so i thought i missed something out. now for my question: IF, i had to use alter, How do i alter the table/PK Constraint to modify the EmailID field and make it Unique IF i decided to drop the table and made a new one, how do i make those two primary keys uniqe? Thanks a bunch!!

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  • Problem with auto increment primary key (MySQL).

    - by mathon12
    I have 2 tables each using other's primary key as a foreign key. The primary keys for both are set to auto_increment. The problem is, when I try to create and entry into one of the tables, I have no idea what the primary key of the entry is and can't figure out what to put in the other table as a foreign key. What should I do? Do I drop auto_increment altogether and cook up a unique identifier for each entry so I can use it to address the created entries? I'm using PHP, if that's relevant. Thanks.

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  • Timestamp as part of composite primary key?

    - by Curtis White
    I get this error when using linq-to-sql with timestamp as part of a composite primary key: "The primary key column of type 'Timestamp' cannot be generated by the server." I'm guessing this may be due to the fact timestamp is just a row version thus perhaps it must be created after the insert? Or...

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