0
votes
2answers
100 views

When do you use subquery in SQL? [on hold]

When do you use subquery in SQL, and what type of request is subquery useful for? I am practicing SQL and need to know how to spot a subquery problem immediately
78
votes
10answers
10k 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 ...
0
votes
1answer
85 views

Why doesn't MySQL have an explicit “No Limit” option for queries?

I use SQLyog Community edition and like many other SQL applications out there it puts a 1000 result limit on queries that do not have a limit provided. I am wondering why MySQL doesn't have an ...
2
votes
3answers
58 views

Select custom output formats from database with SQL

I am planning to make a simple rest service application, and I am currently deciding the architecture. I have decided that I want to write the middle layer in multiple languages, so that it is easy to ...
3
votes
3answers
372 views

Is it better to use a switch statement or database to look through 5,000 to 10,000 instances?

I have some JSON data in this format (5,000 instances for now): {"id":"123456","icon":"icon.png","caseName":"name of case"} I am allowing the user to search for the name of the case and then return ...
3
votes
1answer
174 views

Best way to rename existing unique field names in database?

I have a database table that contains id, filename, userId id is unique identifier filename should also be unique table may contain >10000 records When a user uploads a file it should be ...
1
vote
1answer
117 views

Store data for multiple User Type

I am developing an app where four types of user share same module. So is it a good idea to create: one table and user_type and user_id (something like that) table prefixes basically 4 diff tables of ...
1
vote
2answers
1k views

Using Autoincrement Primary keys as Foreign Keys

When creating a table, there is an option for us to set the numeric primary key as autoincrement where it's value increases whenever a new data in inserted. This primary number can be used for ...
0
votes
1answer
298 views

Are there any SQL servers that support compiled queries?

Can SQL queries be compiled into byte code or equivalent to enhance performance? I know that most database servers support prepared statements, but is that the same thing as compiling? Most ...
3
votes
7answers
813 views

OOP (php) for beginners - some unclarities

I started reading some tutorials about OOP, because I want to learn the basics. I have a question about it. I understand how you can have a object "Car" and give it a color like this ...
1
vote
2answers
427 views

Why OTServs have an item cloning problem if the server crashes? [closed]

OTServs are open source MMORPGs with a huge community. Mostly all of them have a serious problem: if the server crashes, people can clone items. This is a dirty trick that can be executed because the ...
109
votes
13answers
38k 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 ...
1
vote
5answers
914 views

Is it Considered Good SQL practice to use GUID to link multiple tables to same Id field?

I want to link several tables to a many-to-many(m2m) table. One table would be called location and this table would always be on one side of the m2m table. But I will have a list of several tables ...
0
votes
1answer
987 views

How to check for null in most sql's - “column is null” or “column = null” [closed]

I'm not sure of the right syntax to use. Is it select * from tlb where flag is NULL or select * from tlb where flag = NULL Is the answer the same for oracle, sqlserver and Postgres?
2
votes
2answers
177 views

Better way to search for text in two columns

Here is the scenario. I am making a custom blogging software for my site. I am implementing a search feature. It's not very sophisticated - basically it just takes the search phrase entered and runs ...
4
votes
3answers
331 views

Rule of thumb for field sizes

What VARCHAR sizes should be used for first and last names, phone numbers (preferably international), email adresses, urls, dictionary words and file names? Edit: Zapped the introductory phrase to ...
3
votes
7answers
3k views

What is the best approach for database design with lots of columns?

I am writing a query based financial application. It lets the user to write complicated equations (much like WHERE part of an SQL query) and find companies matching those criteria. For the above, I ...
5
votes
2answers
178 views

Storing stop/start points in a database

Let's say I am storing start and stop points per user into a database table. For example... let's say in a chat system, a user only needs to see lines 24-293, and 500-512. (Let's say he logged off ...
3
votes
3answers
755 views

Why put SQL statement in a variable before using mysql_query()?

I'm been working with PHP on and off for a bit now, and I've seen plenty of code both ways: $sql = "SELECT …"; mysql_query($sql); vs mysql_query("SELECT…"); Is there a reason for separating the ...
0
votes
1answer
123 views

Which EXPLAIN SELECT is better — the one in PostgreSQL or the one in MySQL? [closed]

Or are the two basically the same when it comes to figuring out how to build the right indexes?
8
votes
9answers
3k views

Foreign key restrictions -> yes or no?

I would like to hear some”real life experience” suggestions if foreign key restrictions are good or bad thing to enforce in DB. I would kindly ask students/beginners to refrain from jumping and ...
12
votes
2answers
1k views

Best way to organize SQL queries stored in your code ? (or should you?)

I am sure I am not the only one who gets frustrated when they see a page of code littered with SQL queries. The ActiveRecord and other ORM patterns help mitigate a good amount of SQL used in a ...