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.

learn more… | top users | synonyms

2
votes
0answers
54 views

Storing URLs in a database

I am thinking about storing URL's in my database, but I am not sure whether the way I use is an efficient way to do things or not. Table name : url url_id (Primary Key & Auto Increment) url_value ...
2
votes
1answer
759 views

unique constraint violated (ORA-00001) in concurrent insert [closed]

I have a procedure that is called from concurrent transactions: //Some actions here INSERT INTO table1 (table1_id, table1_val1, table1_val2, table1_val3) VALUES ...
2
votes
2answers
468 views

Replacing composite key with surrogate

I have the following table that has a couple of million rows in it and is 99% fragmented virtually all of the time. My plan was to insert a IDENTITY field as a surrogate key to replace the current ...
2
votes
0answers
365 views

Why are runtimes different for a table including a primary key versus a table with a clustered unique index added after population [closed]

When I create a temporary table with a PK defined from the outset like this I get great performance in subsequent joins on that key: create table #temp ( field1 int not null field2 int ...
1
vote
2answers
2k views

Is it recommended to use Identity as an alternative to primary key?

We can declare an Identity like id_num so that id_num will have an increment of unique numbers. CREATE TABLE new_employees ( id_num int IDENTITY(1,1), fname varchar (20), minit char(1), lname ...
1
vote
2answers
156 views

How do I create a rule for a Primary Key

I am using SQL Server 2005 and I need to create a primary key with an alpha character and 3 numbers together: p001 b201 I know I need to create a rule and bind that rule to the primary ...
1
vote
3answers
444 views

Normalization: 'zip code' as a primary key

I've seen frequently that you should not have all address fields (zip, street, city, state, country, etc) in the same table as your user info table (pk_id, name, email... ). This would be in ...
1
vote
2answers
2k views

What could cause an auto increment primary key to skip numbers?

I have a table created with the following T-SQL: CREATE TABLE [dbo].[TableName]( [id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY CLUSTERED ( [id] ASC )WITH (PAD_INDEX = OFF, ...
1
vote
1answer
836 views

does last_insert_id() returns correct result when writes from multiple sessions?

I have a table in which there is a combination of 4 columns that will act as a unique key. Instead of using a composite primary key, I want to keep an id column as the primary key. This field is on ...
1
vote
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 ...
1
vote
2answers
89 views

What Columns to create Indexes on?

I have a table , which contains upto 20 columns. The data is selected, inserted, and deleted by 3 columns: Username, StartDate, and EndDate. These 3 columns are NOT unique. The table is a ...
1
vote
3answers
61 views

does the mere existence of a primary key increase query speed for large data sets?

So, I have a table with about 2.4M rows and ~30 columns. There is no unique column within the data. The data is transaction logs from stores where each transaction number is only unique on a per store ...
1
vote
1answer
148 views

What's better here - a single column or multicolumn primary key?

Let's assume you have a table groups and a table item. Each item belongs to exactly one group. It is an inherent part of that group. An item cannot exist outside of a group and it cannot be moved to ...
1
vote
1answer
77 views

When do you add your foreign keys?

I'm scripting out a fairly simple database so I can simply hand off a script to someone else for an application to use. I'm curious about where best practice/the community stand on this: When should ...
1
vote
1answer
3k views

What is the difference between Primary key and Super key in DBMS

I am new to DBMS and I am still learning the theory. I am getting really confused with this key business and after googling I have narrowed it down to just 2 keys I dont get (primary and super key) ...
1
vote
2answers
3k views

How are auto_increment keys handled in INSERT (SELECT * FROM…)

I have table1 and table2 in MySQL. Both have a primary auto_increment key id. If the table schemas match and I do INSERT INTO table1 (SELECT * FROM table2) what happens with regards to the new rows ...
1
vote
1answer
1k views

Auto Increment Primary ID inserting random values

Today I was asked to look into this problem and I have never seen anything like this before. A table in our MySQL database, with a primary IDs column, which is set to autoincrement int, had some weird ...
1
vote
1answer
160 views

Multiple primary keys

I am new to database design and have been looking at some example data models here. One thing I don't understand is if you have a table like client_addresses from the link above: ...
1
vote
2answers
538 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 ...
1
vote
1answer
68 views

“Transitive” keys

I have a central table, A, which will have a key that I'll call A_ID. Now, I have a table B in a "one to many" relationship with A (many B's map to one A). Each link will, of course, have a link ...
1
vote
2answers
77 views

Relationship with a table without unique/primary key

I have a database with 3 tables. Table Work, with a field named workName. Table SubWorks, which have a field subWorkName and work with a relationship with Work.workName. And table Activity with ...
1
vote
1answer
1k views

Multiple primary keys in PostgreSQL

I have the following table: CREATE TABLE word( word CHARACTER VARYING NOT NULL, id BIGINT NOT NULL, repeat INTEGER NOT NULL ); ALTER TABLE public.word OWNER TO postgres; ALTER TABLE ONLY word ADD ...
1
vote
1answer
186 views

How do I validate all my constraints in postgresql?

It seems like I have been bitten by the first bug described in the release notes of postgresql 9.3.4: http://www.postgresql.org/docs/devel/static/release-9-3-4.html I now have e.g. duplicate primary ...
1
vote
2answers
142 views

Column suitable for natural key?

I have read many articles now about natural vs surrogate primary keys, and came to the conclusion there is no single best practice. I have a table that will have around 2000 definite unique values, ...
1
vote
1answer
220 views

MySQL, temporary on disk table on primary key retrieval?

MySQL 5.5.24, Windows 7 64-bit. I've InnoDB table with primary key defined on three columns: CREATE TABLE `common_descriptions` ( `object_id` mediumint(8) unsigned NOT NULL DEFAULT '0', ...
1
vote
1answer
187 views

MySQL looking up more rows than needed (indexing issue)

In our MySQL 5.5 database, we have following InnoDB table with 30M+ rows: +----------------+-------------+-----------------+--------+ | participant_id | question_id | given_answer_id | status | ...
1
vote
2answers
115 views

Relations, dependencies and normal form

I have some issues in understanding about relations and dependencies. I will show two examples and what I want to know: Assume the relation GTX {G,T,X} with the following dependencies: G,X -> T ...
1
vote
1answer
172 views

Is there a way to extract a report of or script all of the primary keys in a database?

I have just discovered that deployed copies of one of our databases have no primary keys. This is probably the fault of the SSMS Import/Export wizard, which has done the same to me. Our master copy of ...
1
vote
1answer
537 views

Missing PK/FK after database migration

We recently had a server migration. A new server is now the PROD server, and what used to be the PROD server is now the staging environment. Apparently, the data was transferred correctly, but the ...
1
vote
1answer
602 views

How to alter primary key constraint for 2 columns in same table in SQL Server?

In SQL Server, I already created a table called tblDatabase with some columns. I want to add a primary key on the two columns DatabaseName and Servername. I tried to add: ALTER TABLE tblDatabase ...
1
vote
1answer
649 views

DynamoDB: searching with primary key or range key, which way is faster?

To those familiar with DynamoDB, I'm trying to make a table where items only have 2 entries. For example, . Most of the time I'll be searching the user_id with a facebook_id on hand. Amazon's ...
1
vote
1answer
2k views

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 ...
1
vote
1answer
1k views

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 ...
1
vote
1answer
37 views

How to insert values into a junction table?

I add values into my two tables using the code below, but I also have a junction table called book_main_cover and I want to add data into this table to make a connection between book_id and ...
1
vote
1answer
40 views

How can one drop all default values and allow NULL for all columns of a table?

I'm working on a PHP script to modify the primary key (PK) of a table. My current code is: $q = "SHOW KEYS FROM $db.$table WHERE Key_name='PRIMARY';"; $keys = Query ( $q); if ( $keys) { $q = ...
1
vote
1answer
52 views

Foreign Keys to tables where primary key is not clustered index

I'm focusing on SQL Server here, but I think this is a database agnostic question, really. I have a table whereby a Guid is logically the primary key. However, uniqueidentifiers apparently make ...
1
vote
1answer
556 views

Composite primary key from multiple tables / multiple foreign keys

I want to build a composite primary key made up of foreign keys from two different tables. I'm still pretty green to this... A great answer was given to building a composite key from multiple foreign ...
1
vote
1answer
82 views

Almost sequential GUIDs vs random GUIDs?

I'm looking at using GUIDs (UUID) as primary key with clustered index in SQL Server. In my webb-app I have many clients who will create items client side in javascript and save them only now and ...
1
vote
2answers
64 views

compound primary key with separate id field for reference

I am trying to build locations into a database like so: Country -> Region -> Town Countries will be populated with a list of pre-defined worldwide countries, regions & towns are input by users. ...
1
vote
1answer
51 views

one to one relationship

This is my database structure: Users {user_id, username} Profiles {profile_id, user_id, user_views} My question is: If I do it the way mentioned above, should I to set user_id as primary key or ...
1
vote
1answer
231 views

MySQL auto_increment delivers different primary key in MyISAM and InnoDB

I have a table with auto incremental primary key. If I want to change a row and add new rows I got different primary keys depending on engine MyISAM and InnoDB. The original table is: pk.. ...
1
vote
1answer
336 views

Would Mongo's ObjectID work well in InnoDB's clustered index?

Mongo's ObjectID is defined like this: ObjectId is a 12-byte BSON type, constructed using: a 4-byte value representing the seconds since the Unix epoch, a 3-byte machine identifier, ...
1
vote
1answer
112 views

Key lookup partition pruning

I have a query inner joining multiple tables all of which are partitioned and have 10 partitions each: SELECT A.COL1, B.COL2, C.COL3 FROM A INNER JOIN B ON A.ID = B.ID INNER JOIN C ON A.ID = C.ID ...
1
vote
1answer
137 views

Is there a tuning parameter for MySQL that allows you to set an on-disk gap between non-sequential primary keys?

I understand that one of the primary issues with using a non-sequential primary key is that every disk/memory write that does not come after the last known key causes a re-write of everything from the ...
1
vote
1answer
109 views

Can I place the attribute in the Entity, when the foreign key is also already present?

I am using DBdesigner Fork for generating ER diagram. I have the 'Company' as an entity for which can I place the attribute of 'idShares', despite of having the foreign key of Shares Entity in the ...
1
vote
1answer
551 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 ...
1
vote
2answers
176 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 ...
1
vote
1answer
50 views

choose Username or ID as primary key? [duplicate]

my sites dont need use ID at all, then I am trying to manage user by username. Assume my sites is abc.com, then access to user profile by URL: abc.com/user1 So if you want to view all info of that ...
1
vote
0answers
41 views

How to determine next value to use in composite key in SQL Server? [closed]

I am trying to figure out how to determine the next value to use when adding a new record to a table that uses a composite/compound primary key in a system with concurrent users. Suppose I have an ...
1
vote
2answers
51 views

Primary Key choice on table with unique identifier

I'm reconsidering my choice of Primary Key on a table, and would like some input. Some context: We are building a REST API, where clients access "Assets" identified by a GUID. So, the table for ...