relational-database

Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice? Based on the responses let me

I new in database design. What is better option for product attribute database design for cms?(Please suggest other options also). option 1: 1 table products{ id product_name color price attribute_name1 attribute_value1 attribute_name2 attribute_value2 attribute_name3 attribute_value3 } option 2: 3 tables products{ id product_name color price } attribute{ id name value } products_attribute{ products_id attribute_id } Bill Karwin You're making a common mistake of database design, storing name in one column and value in another column. This is not a relational database design. Each attribute

I'm using two online sources for gaining an understanding of the 5NF, without any rigor of Math and proofs. A Simple Guide to Five Normal Forms in Relational Database Theory (by Kent. This one seems to have been reviewed and endorsed in one of his writings by none other than CJ Date himself) Fifth Normal Form (Wikipedia article) However, I'm unable to understand either of these references! Let's first examine Reference #1 (Kent's). It says: "But suppose that a certain rule was in effect: if an agent sells a certain product, and he represents a company making that product, then he sells that

What is the real difference between one-to-many and many-to-one relationship? It is only reversed, kind of? I can't find any 'good-and-easy-to-understand' tutorial about this topic other than this one: SQL for Beginners: Part 3 - Database Relationships Devendra D. Chavan Yes, it a vice versa. It depends on which side of the relationship the entity is present on. For example, if one department can employ for several employees then, department to employee is a one to many relationship (1 department employs many employees), while employee to department relationship is many to one (many employees

I have created a database in Access and right know i have to write a report. I know that the databasesystem has three forms of schemas: physical, conceptual and external. Does the following ER diagram (by using the method normalization ) belongs to the conceptual level?: Or does this belong to the conceptual level?(incl. ref integrity): As for the phisical schema, does this include the integrity rules? The Three-level ANSI-SPARC Architecture aka three schema approach : An external schema is the database (with metadata including constraints) as seen by some user, a view of the conceptual schema

I have EXPERIMENTAL_RUNS (runId), each of which have any number of SENSORS (sensorId) associated with them. With that in mind, I have an RS table to join the two: ========== RS ========== runId, sensorId Thus if the run with runId=1 had sensors with sensorId=1, sensorId=6, sensorId=8 in it, there would be 3 entries in the RS table: (runId=1, sensorId=1) (runId=1, sensorId=6) (runId=1, sensorId=8) Is this really how I would return all EXPERIMENTAL_RUNS that have sensors {11,13,15}? From what I've read, what I seem to want is a nested hash join... Is this what's going to happen? SELECT a.runId

As I am in the final stages of setting up a database for one of my projects, I have thought of an additional constraint that would need to be added to the Task table (see image below), but I am not sure how this can be implemented in MySQL. Original Database Schema (without markups): Click here. Database Schema with Markups: For each job ( job ), a WBS Code List ( wbscodelist ) is assigned. Each of these lists contain a number of WBS Codes ( wbscodeitem ) that apply to that job. An example would be: Job A uses WBS Code List #1 Job B uses WBS Code List #2 Job C uses WBS Code List #1 etc. WBS

Because MySQL does not have a built in relational division operator, programmers must implement their own. There are two leading examples of implementations which can be found in this answer here. For posterity I'll list them below: Using GROUP BY/HAVING SELECT t.documentid FROM TABLE t WHERE t.termid IN (1,2,3) GROUP BY t.documentid HAVING COUNT(DISINCT t.termid) = 3 The caveat is that you have to use HAVING COUNT(DISTINCT because duplicates of termid being 2 for the same documentid would be a false positive. And the COUNT has to equal the number of termid values in the IN clause. Using JOINs