0
votes
0answers
45 views

Error adding constraint foreign key to bridge table

Hi there I am fairly new to sql development. I am current following the head first into mysql book and is on chapter 6. On chapter 6 there is a table in third normal form but it does not contains the ...
0
votes
1answer
30 views

Conditional when creating a domain

How can I define or change a domain based on another attribute value? F.e. domain for salary is a numeric value > 500. But if a date the person was hired > January 1st, 2013, then the salary must be ...
1
vote
1answer
258 views

Constraint based rules engine

I am evaluating software systems which configure products that tout constraint based versus rules based engines. Can someone explain (with maybe an example or two) to a non-expert what the difference ...
5
votes
2answers
285 views

Defining constraints in `CREATE TABLE` statements

Recently I have been using a Database Abstraction Layer built by a Python web-framework called web2py (click for their DAL syntax). They include the option to include your constraints within the ...
1
vote
2answers
346 views

Only one NULL for one part of primary key

I have two date columns : "start date" and "finish date". I want to make sure that there can be only one null value in the "finish date" column (which should be current state if it's NULL) for one ...
2
votes
2answers
892 views

SQL set allowed values for a column

I want to make an ALTER TABLE expression which adds a new column and sets a default value and additionaly defines the allowed values for that column. It's a text column, and allowed should be only ...
3
votes
2answers
151 views

Finding violations of the symmetry constraint

Suppose I have a table Friends with columns Friend1ID, Friend2ID. I chose to represent each friendship with two records, say (John, Jeff) and (Jeff, John). Thus, each pair of friends should show up ...
1
vote
3answers
182 views

is id and phone number enough to uniquely identify a row in phone numbers

Was designing a table a customer_phone_numbers table a while back, which only purpose was to allow us to store as many phone numbers as a user wanted to have on file. I originally came to the ...
5
votes
1answer
168 views

Oracle: DB *partial* constraint?

I am pretty new to Oracle and the database world. I am not sure if the title makes any sense at all, so I'll just go ahead and explain my situation. I currently have a table at hand that records ...
1
vote
2answers
1k views

Usage of RESTRICT or No ACTION in FOREIGN KEY Constraints

Sorry if this question is naive, but I was unable to understand possible usage of RESTRICT or No ACTION. Consider a simple database of CREATE TABLE column1 ( first_id int(11) NOT NULL AUTO_INCREMENT, ...
13
votes
3answers
7k views

PostgreSQL multi-column unique constraint and NULL values

I have a table like the following: create table my_table ( id int8 not null, id_A int8 not null, id_B int8 not null, id_C int8 null, constraint pk_my_table primary key (id), constraint ...
5
votes
6answers
393 views

Running a database without constraints

We're looking at utilizing a new proprietary high performance database engine for OLAP and OLTP scenarios. One important aspect of it right now is that it does not support foreign key or other ...