This tag is for general database questions; if you question is specific to SQL use that tag instead.

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146
votes
13answers
81k views

Why use a database instead of just saving your data to disk?

Instead of a database I just serialize my data to JSON, saving and loading it to disk when necessary. All the data management is made on the program itself, which is faster AND easier than using SQL ...
109
votes
16answers
6k views

How do you store “fuzzy dates” into a database?

This is a problem I've run into a few times. Imagine you have a record that you want to store into a database table. This table has a DateTime column called "date_created". This one particular record ...
92
votes
10answers
26k views

Why is “Select * from table” considered bad practice

Yesterday I was discussing with a "hobby" programmer (I myself am a professional programmer). We came across some of his work, and he said he always queries all columns in his database (even on/in ...
91
votes
12answers
96k views

Is it a bad practice to store large files (10 MB) in a database? [closed]

I am currently creating a web application that allows users to store and share files, 1 MB - 10 MB in size. It seems to me that storing the files in a database will significantly slow down ...
90
votes
8answers
58k views

When would someone use MongoDB (or similar) over a Relational DBMS?

Im a bit confused......the whole NoSQL and such. When would you choose to use something like MongoDB over something like Oracle or MYSQL? I dont really understand....the "difference" as far as usage ...
64
votes
7answers
6k views

How does a surname of Null cause problems in many databases?

I read an article on BBC. One of the examples they said was that people with surname 'Null' are having problems with entering their details in some websites. No explanation is given about the error ...
63
votes
16answers
5k views

Co-worker renamed all of my queries [closed]

I don't know if I should be very irritated or what. I single handedly built over 300 queries for a large database, and developed a naming convention so I could find them later. No one else in my ...
60
votes
10answers
6k views

Is it premature optimization to add database indices?

A colleague of mine today suggested that we go through all of the queries in our application and to add indices accordingly. I feel this is premature optimisation because our application is not even ...
60
votes
6answers
3k views

Is this a ridiculous way to structure a DB schema, or am I completely missing something?

I have done a fair bit of work with relational databases, and think I understand the basic concepts of good schema design pretty well. I recently was tasked with taking over a project where the DB was ...
58
votes
7answers
6k views

Why does the relational model for a database matter?

I am approaching a project where I'll be having to implement a database with my boss; we're a very small start up so the work environment is deeply personal. He had given me one of the company ...
55
votes
11answers
77k views

SQL: empty string vs NULL value

I know this subject is a bit controversial and there are a lot of various articles/opinions floating around the internet. Unfortunatelly, most of them assume the person doesn't know what the ...
52
votes
6answers
11k views

Should Latin-1 be used over UTF-8 when it comes to database configuration?

We are using MySQL at the company I work for, and we build both client-facing and internal applications using Ruby on Rails. When I started working here, I ran into a problem what I had never ...
52
votes
2answers
50k views

Creating database connections - Do it once or for each query?

At the moment I create a database connection when my web page is first loaded. I then process the page and run any queries against that conection. Is this the best way to do it or should I be creating ...
51
votes
12answers
4k views

Database source control

Should database files(scripts etc.) be on source control? If so, what is the best method to keep it and update it there? Is there even a need for database files to be on source control since we can ...
51
votes
6answers
17k views

How much business logic should the database implement?

I've worked in some projects where most of the business logic was implemented on the database (mostly through stored procedures). On the other side, I've heard from some fellow programmers that this ...
48
votes
13answers
6k views

Is it necessary to create a database with as few tables as possible

Should we create a database structure with a minimum number of tables? Should it be designed in a way that everything stays in one place or is it okay to have more tables? Will it in anyway affect ...
44
votes
14answers
8k views

Is there any reason not to go directly from client-side Javascript to a database?

Possible Duplicate: Writing Web “server less” applications So, let's say I'm going to build a Stack Exchange clone and I decide to use something like CouchDB as my backend store. If I use ...
43
votes
6answers
3k views

Business logic: Database vs code [duplicate]

I'm a student of systems engineering, and all my teachers and friends (that actually work in the area) say that it is better to have as much logic as possible implemented in the database (queries, ...
42
votes
8answers
6k views

Is the use of NoSQL Databases impractical for large datasets where you need to search by content?

I've been learning about NoSQL Databases for a week now. I really understand the advantages of NoSQL Databases and the many use cases they are great for. But often people write their articles as if ...
42
votes
8answers
39k views

Create my own database system [closed]

I need to learn how databases work in order to use them more efficiently, and my way of learning is by doing. I want to create my own database system. I am not referring to creating a pseudo-database ...
41
votes
1answer
15k views

How is localStorage different from indexedDB?

localStorage and indexedDB are used for offline storage of data in HTML5. What are their key differences and which one is preferable in what situations?
40
votes
4answers
15k views

Is backing up a MySQL database in Git a good idea?

I am trying to improve the backup situation for my application. I have a Django application and MySQL database. I read an article suggesting backing up the database in Git. On the one hand I like it,...
40
votes
11answers
3k views

Why don't relational databases support returning information in a nested format?

Suppose I'm building a blog that I want to have posts and comments. So I create two tables, a 'posts' table with an autoincrementing integer 'id' column, and a 'comments' table that has a foreign key '...
39
votes
7answers
5k views

Does using a database server make sense if the application only does things locally?

I've seen some applications that are basically application software that run local to the system (so they don't have communicate much over the network). These applications seem to depend on database ...
36
votes
8answers
5k views

Why would you store an enum in DB?

I've seen a number of questions, like this, asking for advice on how to store enums in DB. But I wonder why would you do that. So let's say that I have an entity Person with a gender field, and a ...
35
votes
12answers
3k views

Should experienced programmers know database queries? [closed]

There are so many programmers out there who are also an expert at Query writing and Database design. Should this be a core requirement to be an expert programmer or software engineer? Though there ...
32
votes
6answers
4k views

What is a good security practice for storing a critical database on developer's laptops?

We have a few givens: Developers need a replica of the production database on their machines. Developers have the password to said database in the App.config files. We don't want the data in ...
31
votes
5answers
4k views

No central database

I have a client that is looking to get a website/mobile apps/desktop apps built that deal with very sensitive data (more sensitive than bank/card details). Because of the sensitive nature of the data, ...
30
votes
4answers
12k views

Achieving Zero Downtime Deployment

I am trying to achieve zero downtime deployments so I can deploy less during off hours and more during "slower" hours - or anytime, in theory. My current setup, somewhat simplified: Web Server A (....
27
votes
4answers
8k views

How do you decide what kind of database to use?

I really dislike the name "NoSQL", because it isn't very descriptive. It tells me what the databases aren't where I'm more interested in what the databases are. I really think that this category ...
26
votes
5answers
4k views

Why don't Windows/Linux use relational Databases (RDBMS)?

Why don't Windows/Linux use relational databases (RDBMS)? I know they use file systems to store all data but don't you think it is more efficient to use databases like we use in web sites/web apps? ...
26
votes
7answers
9k views

How to suggest using an ORM instead of stored procedures?

I work at a company that only uses stored procedures for all data access, which makes it very annoying to keep our local databases in sync as every commit we have to run new procs. I have used some ...
26
votes
8answers
9k views

Front end first or Back end first. Of the two which is a Good system design pratice?

I have a client right now requiring me to develop a school enrollment system. Now this is the first time im having this kind of challenge. Most of the past software that i created are not that complex....
25
votes
2answers
15k views

Data Synchronization in mobile apps - multiple devices, multiple users

I'm looking into building my first mobile app. One of the core features of the application is that multiple devices/users will have access to the same data -- and all of them will have CRUD rights. I ...
23
votes
1answer
13k views

When should you use a document vs relational vs graph database? [closed]

For the purposes of discussion let's consider a FourSquare scenario. Scenario Entities: Users Places Relationships: Checkins: users <-> places, many to many Friends: users <-> users, ...
22
votes
16answers
3k views

Why aren't databases integrated as a language feature?

Are there any programming languages that have a built-in database as a first-class language feature rather than connecting to an external SQL (or other) database? What would be the drawbacks and ...
22
votes
9answers
10k views

Should we ever delete data in a database?

I am new to databases and trying to understand the basic concepts. I have learned how to delete data in a database. But one of my friends told me that you should never delete data in a database. ...
22
votes
6answers
15k views

Should I use one database per application or share a single database amongst multiple applications [closed]

I have multiple applications some that use data from the same sources. Is it best practice (or what are the pros/cons) to: leave the data in databases shared by multiple applications saves space ...
21
votes
12answers
8k views

What are the advantages of storing xml in a relational database?

I was poking around the AdventureWorks database today and I noticed that a number of tables (HumanResources.JobCandidate and Sales.Individual for example) have a column which is storing xml data. ...
21
votes
3answers
8k views

Should I use a config file or database for storing business rules?

I have recently been reading The Pragmatic Programmer which states that: Details mess up our pristine code—especially if they change frequently. Every time we have to go in and change the code to ...
21
votes
3answers
15k views

Is there any reason to use varchar over text columns in a database?

Is varchar just a remnant from before text came around, or are there use cases where you would want to use a varchar? (Or char for that matter..) (I use Postgres and MySQL (MyISAM) daily, so those ...
21
votes
5answers
3k views

Databases and Unit/Integration Testing

I have had a discussion with someone about unit/integration testing with web applications and I have a disagreement about 1 core idea. The issues is that the person I am talking to think that the ...
20
votes
9answers
2k views

In agile development, should I try persistence in flat file before database?

Somebody explained to me that since in agile development, policy and the application logic should be more important than details such as persistence method, persistence decision should be taken at the ...
20
votes
6answers
11k views

Unit-Tests and databases: At which point do I actually connect to the database?

There are answers to the question on how test classes that connect to a database, e.g. "Should service test classes connect ..." and "Unit testing - Database coupled app". So, in short let's assume ...
19
votes
6answers
3k views

Advantages and disadvantages of using bit masks in database

Not so long ago I talked to my colleague and he was definitely against using bit masks because it is hard to understand all the values that are stored in the database. In my opinion it is not always a ...
19
votes
7answers
3k views

Does it make sense to standardize including a created date and last updated date field on all DB tables?

My boss is currently attempting to apply some development standards to our team, so we had a meeting yesterday to discuss the standards which was mostly going well until she brought up: All DB ...
19
votes
4answers
630 views

Using flat files vs database/API as a transport between a frontend and backend

I've got an application which has generated a rather heated discussion between a couple of the developers. Basically, it's split into a web layer and a backend layer. The web layer collects ...
18
votes
7answers
2k views

Safely fixing production database data

Bugs happen and sometimes data has to be fixed in production. What is the safest way to go about this from a big company standpoint? Are there tools that can help? Here are some considerations driving ...
18
votes
5answers
12k views

What is the difference between all-static-methods and applying a singleton pattern? [duplicate]

I am making a database to store information about the users of my website (I am using stuts2 and hence Java EE technology). For the database I'll be making a DBManager. Should I apply singleton ...
18
votes
3answers
11k views

Is there a list of common usernames to reserve in a new system?

I need to reserve usernames in my new website. These generally fall into three categories 1) usernames no-one should have (eg: admin, user, service, help, root, etc) 2) names of super famous people ...