Most voted "database" questions
A database (its abbreviation is BD, DB, database) is an organized collection of data typically used to model certain situations. Use this tag if you have questions about designing a database. If this is a specific database management system, like Mysql, for example, use this tag instead.
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answer13017
viewsTuples in a database
I know what a Python tuple is but not in a database, so follow the question: What is a tuple in the database context?
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answers2119
viewsWhat is it, Trigger?
I was looking about triggers on this site, but found no question about triggers and then: What are Triggers? When to use a Trigger? How to use a Trigger? What are the uses and applicability of…
databaseasked 8 years ago Igor Contini 663 -
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answers701
viewsWhat would be DSN?
Whenever I see someone preparing some configuration for database, I see appearing the term DSN. I see it happening in the parameters of PDO (class to connect to PHP Database). Example: $dsn =…
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answers808
viewsHow to save program settings, database or configuration file?
In my application, the admin user, can make some settings, for example: Configure if you want to use specific product templates, or stay open for the end user to type. Configure if you want to use…
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answer4174
viewsHow to concatenate lines?
How to concatenate all the results of a query in SQL Server in order to return all information in one variable? For example, considering a table cliente with the following composition:…
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answer1008
viewsWhat are the most common types of databases for web applications?
Some databases store objects, relational structure of tables, hierarchies, etc. What are all these types (models)? When is each application indicated (besides, of course, the developer’s…
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answers12428
viewsWhat’s the difference between Cast and Convert?
In a Transact-SQL (Ramalho Series) book it is said: CAST AND CONVERT It implicitly converts one expression of data types to another. CAST is synonymous with CONVERT. What do you mean by CAST is…
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answers1193
viewsWhich DBMS to use so that it can be installed on the client’s computer to run a C#application?
I am developing a small C# system that will be implemented on client computers in the future, accessing a local database. Initially I was going to use SQL Server, but I would have to install it next…
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answer649
viewsDo I need to close the connection in each query?
Currently I have a web application that queries multiple databases in the same controller. For each database I request a connection at the server startup and keep them in a static class where the…
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answer1325
viewsRecord records with the mask or remove before?
Contextualizing my question, kind of by convention of my old work environment I always recorded the records without the mask at the base, but a situation arose in my new job where they are saving…
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answers985
viewsWhat are the appropriate scenarios for graph-based databases
Lately I’ve been studying the graph-based database Neo4j. Given that the vast majority of current applications use traditional relational databases, I ask: What are the appropriate scenarios to use…
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answers2984
viewsSurrogate Key and Natural Key
I’m studying about data Warehouse, but I was confused about the concepts of SK and NK. From what I understand, in a DW, a natural key would be a column like foregin key in the table dimension, of…
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answer5110
viewsWhat is Flyway and when to use it?
The system recently drew attention to this issue, and it talks about Flyway. So I’d like to know: what is Flyway? what problems he proposes to remedy? when to use it? what are the competing…
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answers223
viewsIn SQL queries should I follow the order of the index?
If in my table X an index is created with the fields A, B and C (in this order), in the SQL queries I must follow exactly this order? Example following the order of the index: SELECT * FROM X WHERE…
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answers4763
viewsDelete multiple rows from a database
I’d like to delete several figures. For example this would be to delete a line delete from paginasimagens where idPaginasImagens=121; my values are sequentially so a method that is between elements…
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answer94
viewsSQL Server JOINS vs Subquerys
I was making some queries, and came the need to carry out the grouping of a table that was in a JOIN within the query. To illustrate. Sales chart. +----+---------+------------+----------+ | Id |…
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answer151
viewsWhat are index hints?
I saw a comment from @Ricardopunctual that mentioned Density-based index hints your question seems very confusing. it starts with a very basic thing such as "how do I process in sql server", which…
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answers509
viewsGenerate dynamic table with TCPDF
Good afternoon, I’m using the TCPDF to generate an evaluation report, and I need this report to be divided into weeks that the user has activity. At the moment the report is thus What I need is to…
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answers611
viewsWhat is the purpose of using UUID (version 4) as "Primary key"?
I have noticed that some places have switched the ID (generated by autoincroment, depending on SGDB) by UUID, usually use version 4 of UUID which is based on a pseudo-random system, the question is…
database entity-framework laravel-eloquent uuidasked 4 years, 2 months ago Guilherme Nascimento 98,651 -
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answers30736
viewsPermission error when trying to access database
I took a little project already ready to study, only that is giving this error, recently migrated to the Ubuntu and I do not know what to do. Error: SQLSTATE[28000] [1045] Access denied for user…
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answers3255
viewsHow to perform object persistence in Delphi database?
I work with Delphi, but always in a procedural way and using Data-Aware components. I recently started reading some things about working with POO at Delphi, and did some fairly basic examples, my…
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answers194
viewsWhat are database model migrations?
Some MVC frameworks (Rails, Laravel and others) provide database model migrations. What they are, how they work and what are the advantages / disadvantages of using them?
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answers2553
viewsDatabase structure for multi-language system
I already have a system developed, using several tables in the database. I have to start migrating the same to the english and spaniard. The development part I have an idea already (not total), but…
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answers1124
viewsWhen is it worth paying for Sqlserver or Oracle?
Databases open-source how Mysql and Postgres are so advanced that they can serve a wide variety of applications smoothly, perhaps most. (There’s Sqlite too, but this is more for when portability is…
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answers2122
viewsIs it possible to create a Javascript database?
How to create a simple database without using a server? I believe the answer would be no, but check the following: I’m at work and I don’t have access to the databases or even the servers. This way…
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answer1641
viewsHow to Save Colors in Database
I have a simple form, and a TYPE=color. These colors are passed in hexadecimal, but I cannot save in the bank. It gives the following error: Warning: pg_query(): Query failed: ERROR: Invalid input…
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answers11729
viewsInsert line break in field text into database
I have a table with a field type text, the field stores a string imported via archive .csv, the same was inserted without line break and I’m trying to insert it, I was able to identify that the line…
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answers2583
viewsSQL of tables with multiple relationships
How would be the SQL representations of creation and correct insertion of the tables below so that it is possible to have/store the total number of videos of a genre so that it is possible to take,…
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answers766
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answer1481
viewsShould I limit the size of VARCHAR columns for performance?
Normally the maximum size for VARCHAR is 255. If I create the column with a smaller size, say VARCHAR(50), I will gain performance or save disk space?
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answer803
viewsHow to use parse.com?
With the parse.with it is necessary to pass my database to their website? I have a database on the company server, and I don’t intend to put it on their website. They offer the option to access my…
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answers2498
viewsIs there a modeling tool for Nosql database?
I’m doing a database creation project for a web application that will use the Cassandra database. I was wondering if there’s any tools that can help
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answers504
viewsBD for distribution together with java application
Good evening guys, I have a small JAVA application in which some data is entered. I would like to distribute it with an DBMS that does not require download and installation/configuration. I have…
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answer977
viewsInsert data into an External Json
How to insert data into an external Json file: var json = { caminho: "img/minhaIMG.png", descricao: "minha descricão" } How can I enter new data into this json file? In my case, I would use it as a…
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answer384
viewsCategory tree in Mongodb, how to model?
Good night, you guys. As Mongodb changes a lot our way of modeling a database, I came across a question that can be up to half beast. I’m doing a Restful API using Lumen and Mongodb as a database,…
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answer298
viewsWhen to use distributed database?
I would like to know an example in which situation I would need to use a distributed database?
databaseasked 8 years, 10 months ago Miguel Batista 2,812 -
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answers401
viewsHow to create Mysql search that returns lines without matching?
I would like to know how I can do a search that returns records that are not part of the research condition. For example, think about the situation where there is a database of a movie rental…
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answers519
viewsWhat is the best place to store the connection string?
There are some possible places to store the string connecting. Leave tied inside the code, app.config, Windows registry and configuration file. What is the best place to store string connection?…
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answers137
viewsDevelopment in three layers
In a system developed in three layers, I must leave some consistency for the database or I must solve everything in the middle layer? Example: I have a user table, where the name should be unique.…
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answers1201
viewssynchronize Local database with Web
I’m developing an application in Cakephp, with a Mysql database. a part is already working but from the beginning I need a solution to the following problem: My application should work online, but…
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answers345
viewsValues that can be entered as primary key
I have a company code of the product that is formed by two letters and 4 numbers (example: XX0000), it is advisable to use this code as primary key or create another column with code field and put…
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answer1251
viewsHow to filter separate dates by day , month and year in Mysql
Hello, I have a table "Meetings" in Mysql with the following structure: id:Int(11), subject:String(40), day:String(2), mes:String(2), year:String(4), active:String(2) except in the field day the day…
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answers2348
viewsThe following database modeling is in my head?
I created this modeling (just an idea), so there are no null/white fields. I have not completely reviewed it. There may be fields that would remain blank. The matrix table was the Entities and…
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answer2378
viewsWhat are the differences in performance when using querys with EF vs ADO
What is the difference in performance when using the basic query methods SqlQuery<TElement> and ExecuteSqlCommand of Entityframework in relation to directly using the ADO.NET? If there is…
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answers1131
viewsHow does the (anti-)EAV (Entity Attribute Value) standard work?
I would like a functional example, because I do not understand very well this dynamic relationship of creating table of types, with table of data, a dynamic relationship, that many consider…
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answer1911
viewsMaximum size for database tables
What can be the maximum size that a table can have? To make it clearer: a table in Mysql, what is the maximum size it supports? And in SQL Server, Oracle, Postgresql?
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answer382
viewsWhat is the difference between reverse list (Inverted index) and reverse list (Reverse index)?
what concept, characteristics, advantages and disadvantages and an example of use (application).
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answer72
viewsDatabase on Android persists the information?
Does the database lose its information when closing the application? In this case it should be an online database?
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answers324
views"Translate" query from Mysql to SQL Server 2012
What is the SQL Server 2012 query that corresponds to the next Mysql query? REPLACE INTO schedule SET jobname = "sqldump" , last_exec_date = NOW()…
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answer1292
viewsWhat are the disadvantages of using Redis?
There are many advantages to using Redis as a database, but we already know this. I would like to know what the disadvantages of using redis or in which scenarios would be very "against" using it.…