I am designing a database with multiple tables like users, content, etc. I want to allot id to each row in the tables.
So what are the criteria to generate an unique id for each row in each table. And should I make the id in auto increment mode?
Related
I have a table which stores the hash tags as a many to many relation ship
Tags Table
userID - Foreign key
tags - foreign key
I have used Unique constraint which I think is a foolish one.
Here I want to ensure that a user uses the tag a user uses each tag only once in that table.
What query will suit this scenario?
So the desired output is like a user uses only one tag
The database I use is PostgreSQL.
Since I use Django where I have the code below
user = models.ForeignKey("User",unique=True)
userTags = models.ForeignKey("Tags",unique=True)
which has a meaning of that
user column is foreign key reference from User table and it's a unique column
UserTags column is a foreign key reference from Tags table and that column is unique
In my tables for SQL, I have many tables each with an ID column I wish to keep incrementing, along with a main name table with an ID which will be the same value as the corresponding IDs in other tables for the relevant information. I wish to be able to make it so that, when I delete a row from the name table with a certain ID, all values across other tables with the same ID get deleted also. The issue appears to be that, if i create foreign key constraints from the name ID on the name table to the other IDs across other tables, it means these tables are no longer allowed to automatically increment.
Say I have an address table with the addresses of different facilities of a manufacturing company.
The foreign key lets me know which company the addresses belong to, but i need a surrogate id to differentiate between each facility. This id should increment automatically based on the foreign key value.
Note : I just need simple integer values for keys.
eg:
My table has the following columns, ORGANIZATION_ID is the foreign key.
FACILITY_ID is a second surrogate key dependednt on the foreign key.
ADDRESS_TABLE
->ORGANIZATION_ID
->FACILITY_ID
->ADDRESS_LINE_1
->ADDRESS_LINE_2
->CITY
->STATE
->ZIP_CODE
I want the facility id to increase automatically from 1 depending on the
organization id. i.e
ORGANIZATION_ID 1
FACILITY_ID 1
When I insert data for new organization, facility should start from 1
ORGANIZATION_ID 2
FACILITY_ID 1
Next time I insert data for the same organization, my facility id should increment accordingly -
ORGANIZATION_ID 1
FACILITY_ID 2
Is there any way to make this happen in DB2?
I'm currently on DB2 V 10.5.6
No. Auto-increment, or Identity keys as DB2 calls them, don't support composite keys.
Best you could do would be to have a on insert trigger that handled assigning the values you want. Possibly making use of a SEQUENCE; though you'd have to create a new sequence to use for the facilities of each new organization.
Hello the following is schema of the table in question
employee (emp_no,emp_fname,emp_lname,birth_date,residence)
The emp_no is INT and is a primary key. Currently there are random big numbers in the column as IDs and I need to reset the column and make it so that it adds the autoincremented ID to the existing entries plus to every new entry I will add.
I would like to have some explaination about the characteristics of a primary key in the table of such database.This is for vb 2008 express edition,since im new to this language,if this is true, as far as i understand about the characteristic in setting the primary key on each field for true.My question is if you are doing an updates/edit records in your table using the DataContext,if you setup the primary key for true of one of your field in the table it would edit all records in one datarow but if you put the primary key for true in all fields except one of them,all the records in the data column of that field which primary key is false could be edited.Basically its impossible to edit all records in the datarow and all the records in the datacolumn of the table in such one event.
Is there any further explaination about the characteristics of primary key in the table?
The purpose of the primary key in a database table is to identify the field (or fields) that make up a value that uniquely identifies each record on the table. A typical examples are CustomerID in a Customer table; each customer is given a unique ID, and this ID can be used to link the customer into other tables (such as an order table).
Sometimes there are tables where not one single field will contain a unique value for each record. In such cases more than one field can be set as the primary key. In those cases, the combination of values in the primary key fields should always be unique.
So, on the database level, this is not related to the possibility to edit the field or not.
Of course, wikipedia has some content on the subject.