Tagged Questions

In relational database design, a primary key can uniquely identify each row in a table. A primary key comprises a single column or a set of columns.

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How should I save apache logs into a mysql table?

This is a php script to view apache logs. I want to save apache logs into a mysql database. Then add some rules for tagging urls using mysql REGEXP search, like: SET tag='some tag' WHERE url REGEXP ...
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2answers
739 views

Teradata: How to design table to be normalized with many foreign key columns?

I am designing a table in Teradata with about 30 columns. These columns are going to need to store several time-interval-style values such as Daily, Monthly, Weekly, etc. It is bad design to store ...
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2answers
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Index on primary key not used in simple join

I have the following table and index definitions: CREATE TABLE munkalap ( munkalap_id serial PRIMARY KEY, ... ); CREATE TABLE munkalap_lepes ( munkalap_lepes_id serial PRIMARY KEY, ...
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3answers
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Most efficient (or meaningful) way to index grid-based data

I have a MySQL table which I expect to be in surplus of a few million rows and 99% select statements. The problem I am having is coming up with a meaningful way to determine the Primary Key. (I have ...
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4answers
9k views

Mysql int vs varchar as primary key (InnoDB Storage Engine?

I am build a web application (project management system) and I have been wondering about this when it come to performance. I have an Issues table an inside it there are 12 foreign keys linking to ...
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1answer
525 views

SQL - double column used from primary key with autoincrement

I am user the following as primary key in the SqlDB: I am doing the Index as Autoincrement, but it is autoincremented in general not per user. Example userid=1,index=1, then insert another for ...
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3answers
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Differences between “Unique Key” and “Primary Key”

What are the major differences between Unique Key and Primary Key in MySQL?
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1answer
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Does the order of keys in compound Primary key make any difference?

Package Package ------- PackageID PackageName CityID PRIMARY KEY (PackageID) UNIQUE KEY (PackageName) FOREIGN KEY (CityID) REFERENCES City (CityID) Package versions: PackageVersion ...
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3answers
989 views

performance of multi field primary key or 'contrived' 'semi artificial' key

This is not a question regarding the benefits or otherwise of using an artificial auto increment key in any given table against using a multi-field 'primary key'. That discussion (or argument) can ...
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1answer
167 views

Impact of miss-ordered fields in a composite, clustered primary key?

I have tables where the primary key is something like this: -StoreID -BusinessDate Typically, there is one row for every store (~100) for every single day. One row for each store is inserted on a ...
2
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1answer
132 views

Can I use a Clob as a table key (from Java)?

Following a suggestion made to another question to store large amounts of text: can one use a CLOB as primary key field (i.e., from Java's DataNucleus implementation of JDO)? I know it is probably a ...
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1answer
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How is INDEX on Composite Primary Key in mysql?

When making a composite primary key for two or more columns, e.g. PRIMARY KEY(col1, col2, col3); will the system INDEX each column individually? The reason that I am asking this question is that when ...
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4answers
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Two-sided UNIQUE INDEX for two columns

Creating a table with composite PRIMARY KEY or using UNIQUE INDEX for two columns guarantee uniqueness of col1, col2. Is there a tricky approach to make the reverse order of two columns UNIQUE too ...
1
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2answers
172 views

Update primary key

I want to update a primary key column, but the change should cascade to all other child tables where this primary key is used as foreign key. Example: table1 has column "slug" as primary key. One row ...
4
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1answer
855 views

Primary Key Type's Effect on Performance in Oracle?

In MS SQL Server, it is well documented that the type of the primary key can have a dramatic effect on performance. Using narrower types and sequential values significantly improves insert performance ...
2
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2answers
3k views

Single Identity column and composite key, which to make primary?

I've got a table that's a working copy subset of a base table. The base table has a composite key with a clustered index. However I need a single column unique identifier for my framework to work ...
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1answer
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updating mysql primary keys

I need to be able to swap values that are used in a primary key. Meaning, in one update statement, I need to change id 1 to id 2, and id 2 to id 1. In other relational databases, (Sql Server and ...
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2answers
2k views

“on duplicate key update” all the non-key fields mentioned in the insert

How can I update the field values mentioned in the insert portion without listing them again in the on duplicate key update portion? insert into tablename set keyname = 'keyvalue', fieldname = ...
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0answers
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Is it possible to change the data-type of a primary key column in SQL Azure? [duplicate]

Possible Duplicate: How can I alter an existing Primary Key on SQL Azure? OK, so say I have a table: 'Contact' and a primary key: 'ContactID'. The primary key is an INT but I want to ...
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2answers
2k views

Primary key index with a DATETIME as first part of the compound key is never used

I have a problem with INDEXING a DATETIME (or even a date) as first part of my PRIMARY KEY. I use MySQL 5.5 Here are my two tables: -- This is my standard table with dateDim as a dateTime CREATE ...
2
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3answers
446 views

File name as primary key?

I have a few tables I'm going to create for a website, Literature, video, and image. Is there a good reason why I shouldn't use the file name as a primary key. For instance... "someimage.png" as the ...
3
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2answers
279 views

Is index_type ignored on MySQL primary keys in create table?

I have seen a create table whose primary key had an identifier where it should have an index_type, something like that: create table a (foo INTEGER, PRIMARY KEY foo_id (foo)); The thing is that ...
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2answers
1k views

What Is The Point of a Primary Key?

Why do I need to have a primary key on my database for it to function correctly? In every tutorial I read, you need to make the id key the primary key. What does the primary key do differently than ...
2
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2answers
601 views

Generalisation in databases

I am working on a Hospital Management project in DB2. I have one table for staff with a primary key of staff_id. The hospital has to have different staff... e.g doctors,nurses,e.t.c. Is it better to ...
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2answers
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How to promote an existing index to primary key in PostgreSQL

I know how to make a primary key within a table, but how do I make an existing index a primary key? I'm trying to copy an existing table from one database to another. When I show the table, the index ...
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3answers
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SQL table design for primary keys (best practice)

I have a User table that contains the following fields ID (Auto-generated GUID) UserName Password FirstName LastName Email AddressID (GUID) This is linked to the table Address (1-1 relation) which ...
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2answers
502 views

serial field issue

Q: I use a serial as a datatype for my primary keys in my tables. I insert a lot of data then truncate these data one after one many times to test the data entry. My question is: Is there any ...
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3answers
645 views

Need Help Troubleshooting Sql Server 2005 Deadlock Scenario

I am running into a deadlock scenario where the only participants in the deadlock appear to be a single table and a single stored procedure that deletes from that table. I drew that conclusion based ...
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7answers
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Why should I create an ID column when I can use others as key fields? [duplicate]

Possible Duplicate: Why use an int as a lookup table's primary key? So far, I'm accustomed to creating an ID column for every table and it is practical in a way that it makes me not ...
38
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4answers
21k views

When should a primary key be declared non-clustered?

While creating a test database for another question I asked earlier, I remembered about a Primary Key being able to be declared NONCLUSTERED When would you use a NONCLUSTERED primary key over a ...
2
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2answers
914 views

How can an identity primary key index become fragmented?

From what I understand about index fragmentation, this should not be possible. The cases I have found in my databases are non-clustered. Example: ALTER TABLE [dbo].[ClaimLineInstitutional] ADD ...
4
votes
3answers
492 views

What are the pros and cons of using my customer codes as a primary key?

I am designing a database for one of my sales teams. Right now, the goal is to get a master list of customers and their mailing addresses, but the DB will eventually expand to track some other ...
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1answer
7k views

How can I alter an existing Primary Key on SQL Azure?

I want to modify an existing primary key on a SQL Azure table. It currently has one column, and I want to add another. Now, on SQL Server 2008 this was a piece of cake, just did it in SSMS, poof. ...
0
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1answer
339 views

How SQLite index ID (or line number)

SQLite is based on a flatfile, and store virtual tables in a flatfile (I think based on offset, correct me if I'm wrong). But how it index the Primary Key (ID), which I think is identical to line ...
8
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4answers
372 views

What are the performance considerations between using a broad PK vs a separate synthetic key and UQ?

I have several tables where records can be uniquely identified with several broad business fields. In the past, I've used these fields as a PK, with these benefits in mind: Simplicity; there are no ...
25
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5answers
7k views

Working of indexes in PostgreSQL

I have a couple of questions regarding working of indexes in PostgreSQL. I have a Friends table with the following index: Friends ( user_id1 ,user_id2) user_id1 and user_id2 are foreign keys to ...
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3answers
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Should every table have a single-field surrogate/artificial primary key?

I understand one benefit of surrogate/artificial keys in general - they do not change and that can be very convenient. This is true whether they are single or multiple field - as long as they are ...
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1answer
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PostgreSQL: Corrupt primary key, inconsistent table

While recovering from a cloud failure, I found that some tables on a PostgreSQL database are behaving strangely. These tables are indexed using a primary key, but a pg_dump yielded duplicate fields, ...
5
votes
4answers
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MySQL: Why is auto_increment limited to just primary keys?

I know MySQL limits auto_increment columns to primary keys. Why is this? My first thought is that it's a performance restriction, since there probably is some counter table somewhere that must be ...
1
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1answer
140 views

Is it require to fill all tables inside of the database?

Now,I created upper that table and in order to test I will give 3 textboxes values as below. SqlCommand cmd = new SqlCommand ("Insert Into dbo.PrnInf(PrnName, PrnSurName, PrnEgn ) Values ...
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3answers
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What are negative keys used for?

Somewhat new to using standard SQL databases (currently working with MySQL mostly) I haven't run across many usages of this as of yet. When and why is it useful to have negative (or rather signed) ...
6
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3answers
4k views

How can you tell if a table in DB2 has a Primary Key?

We are using a tool that requires specific tables in our DB2 database to have a Primary Key defined. Is there a way using a select statement on the DB to see if a given table has one? Thanks.
4
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4answers
456 views

How much will using a varchar(15) PK affect my tables performance?

I am parsing log file lines from a legacy, proprietary application into a nice easy to query DB. The log lines have no unique integer ID. They do have a UNIX timestamp as an 8 character hex string. ...
4
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3answers
628 views

Can I have create an InnoDB table without a PK? If so, would a secondary index be used as the clustered index?

Is it possible to create an InnoDB table without a Primary Key? Since InnoDB tables are structured as clustered index around the PK, what would be the structure of a table without PK? Would that ...
15
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5answers
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Why use an int as a lookup table's primary key?

I want to know why I should use an int as a lookup table's primary key instead of just using the lookup value as the primary key (which in most cases would be a string). I understand that using a ...
13
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5answers
889 views

Why do primary keys have names of their own?

From a mathematical view, granted that a table has at most one primary key, it seems to be a shortsighted design decision to refer to primary keys by some arbitrary name instead of a simple table ...
2
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1answer
578 views

Question on Design for User + User Groups + User Types + Subscriptions Model

I am redeveloping an existing web application with both weak source code and a weak underlying database design. I'm trying to develop things in a way that future expansion will be much easier, ...
2
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4answers
446 views

Why would i get a duplicate write error of auto-generated primary key?

Hi I'm not a DBA so forgive my ignorance. I don't have access to administrator tools etc. However, I do know that we have a live server which is approaching capacity ie 80%-90% full perhaps. What is ...
7
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2answers
2k views

What's a good way to add a PRIMARY KEY to a large InnoDB table?

I have a table with around 30 million rows in MySQL 5.5 using the InnoDB storage engine. This table has a foreign key that links to another table with around 3 million rows. I want to add a primary ...
12
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2answers
1k views

Is there any tangible difference between a unique clustered index and a clustered primary key?

I understand that there may be a difference in meaning or intent between the two, but are there any behavioral or performance differences between a clustered primary key and a clustered unique index?