Questions tagged [dbms]
Database management systems (DBMSs) are specially designed applications that interact with the user, other applications, and the database itself to capture and analyze data.
84 questions
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DBMS for multiple DB Enviroment Management
I have moved into a DBA role where I now manage multiple types of DBs. I used to manage only MS SQL and MySQL, but now I am managing MS SQL, Azure SQL, MySQL, MariaDB and PostgreSQL. I am currently ...
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Column information from View
Suppose I have this database
CREATE TABLE Students (
StudentID INT PRIMARY KEY,
Name VARCHAR(255) NOT NULL,
Roll INT NOT NULL,
CustomID INT UNIQUE
);
INSERT INTO Students (StudentID, ...
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Where sk = null clause gives an error when used in a query but not in a stored procedure in teradata
In teradata sql I get an error when I use
sel *
from table
where sk = null
However if I include this in a stored procedure and pass a null value in the parameter I don't.
replace procedure(In name ...
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3
answers
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Should i care about field names in JSON datatypes?
In DBMSes like MySQL, MariaDB, PostgreSQL and MongoDB, data is saved as BSON, JSON or JSONB for JSON columns or document.
All of these data types use space for key names in JSON.
Does internal data on ...
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MYSQL workbench like gui tool for oracle 10 g or more
I am a java full stack developer who want to write oracle sql queries to simplify writing is there any mysql workbench like similar gui tool for oracle by oracle or any other please sugest
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2
answers
460
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Update Ledger Table In double entry accounting when there are millions of entries
I am creating an double entry accounting software where I have ledger table along with other tables. My cash account ledger table for is similar to following:
ledger_id
ledger_name
...
1
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1
answer
62
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How does MySQL maintain confidentiality of files?
In a DBMS like MySQL, are the underlying files that contain the data encrypted since we want to have role and user based control? If they are encrypted, what encryption keys and algorithms are used? ...
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Problem associated with transaction schedule
Here, Read_item(B); and B;=B+temp; have written parallelly. what happen here? What is the problem associated with the above transaction schedule?
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Should I use many database in one application?
Currently I am working on a project of a management software. This software is currently in built with an old technology (Codeigniter-PHP). My job is to convert this software to latest technology (...
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1
answer
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Maintenance : File system vs Database
I'm comparing the advantages and disadvantages of File system (journaling and COW) and Database (SQL and Non-SQL). Not only from the developer's point of view, I also want to know further what are the ...
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Print all the row with two or more element in the column
In following table how to print the student number when age occur two or more times, The result should be only column Sno i.e.
Result
Sno
Reason
1
because 18 occur two times
2
because 20 occur ...
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Entity relation with itself
I want to make an ER diagram for scientific research papers, one of the constraints is that a paper shouldn't cite itself.
I'm not very sure how to achieve this, as this question points out, the ER ...
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Are SQL views anything more than saved text?
I am trying to get a better understanding of an answer by @GarethD in https://stackoverflow.com/questions/24188350/incorrect-syntax-near-keyword-option-in-cte-statement?rq=1#answer-24188586 . In that ...
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FInd minimum and maximum number of tuples in R U πA,B ( R⋈S )
Given two relations R(A,B) with r tuples, S(B,C) with s tuples (r>0, s>0), find the min and max number of tuples in this relation:
R U πA,B ( R⋈S )
Given options are:
-min:r, max:r+s
-min:0, ...
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Is Mysql a database management system(DBMS) or a database server?
I can't differentiate DBMS, database server and database client. Mysql, for instance, has Mysql shell, Mysql workbench, etc. If Mysql is a DBMS, then are Mysql shell and Mysql workbench both database ...
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Determine Prime Attributes In this relation. Functional Dependencies are given [closed]
Relation is R(P,Q,C,A,B)
R has the following functional dependencies:
F = { P→QC , CA→B , Q→A , B→P }
What are the prime attributes
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What are the differences between Heap File Organization and Sequential File Organization (Pile Method)
I was learning about File Organization in DBMS, but i found that the Heap File Organization and Sequential File Organization (Pile Method) have the same definition (or maybe i couldn't find any ...
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2
answers
202
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Nosql vs sql for genre management
I'm looking to keep a simple database for movies, with details like Name, YearofRelease, Genre etc. The key factor is the genres entry, where a movie could fall into multiple genres. Using a sql based ...
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What could be the best DBMS to store airbnb data for price prediction [closed]
I have a school project in which I need to predict the airbnb listings prices in 5 different cities.
So I have about 400,000 records each with 19 columns.
All the examples on the internet that are ...
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How does DBMS ensure durability without flushing
I was watching this video, and at a certain point (don't recall the exact minute) the speaker says that the DBMS doesn't immediately flush the file when updates happen. He explains that IO operations ...
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Error 1242(21000) after creating following trigger and performing delete operation
I want to create a trigger which copies the record from maintable to undostack before deleting it in maintable and undostack table acts a stack of 5 records space and this trigger performs a push ...
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no matching unique or primary key for this column-list
My parent table
Create table spare(
Sid int ,
Sname varchar(20),
Mid int,
primary key(Sid,Sname),
foreign key(Mid) references manu(Mid) on delete cascade
);
My child table
Create table Branch(
Bid ...
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3
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Why is a port needed for DBMS?
I always wondered, why a port must be assigned in order to use a DBMS? And what difference does it make using TCP or UDP (and even static and dynamic)?
Is it for communication purposes?
I know this is ...
user218086
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774
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MultiSubnetFailover=true for DBMSes besides SQL Server
A connection string for SQL Server can contain MultiSubnetFailover=true, to handle multiple DNS A records, letting the client try to connect to every IP address of a domain (or subdomain) name, to ...
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1
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Database design normalization elearning portal
Table : Class
Here the className is unique
classId| className
-------|---------
1 | 1st Class
2 | 2nd Class
3 | 3rd Class
4 | 4th Class
Table: Subject
In the Subject table ...
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1
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views
MySQL write performance after truncate & optimize [closed]
Once a year we truncate a table of several GBs and millions of rows and then run optimize in order to shrink the size of the corresponding ibd file on the file system.
However, as this is write ...
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213
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How to start building your own DBMS (based on PostgreSQL)?
I'd like to learn how to make a DBMS (relational), based on PostgreSQL specifically. Not for production purposes to make a commercial product but to learn.
I plan on using C++ but, it's not exactly ...
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Does a primary key contain exactly one Null value...?
My work
A primary key is unique and only one contains for a table.
There are many unique keys that can contain in a table.
In SQL Server, the primary key is not Nullable. But, a unique key may ...
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Suggestion for log storage with search by keywords/tag
I'm trying to find a solution for dealing with a data set of logs of about 500Gb. Ideally what I search for is an index over log message keywords that I parse from the log messages. Like:
Log message
...
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Query NOT Workinng in OPEN OFFICE BASE
select * from "StudentMaster" where "PhoneNo" = NULL;
Syntax error!
i want to see all record which don't Have Phone number !
I have try this all thing.
select * from "StudentMaster" where "...
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1
answer
105
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Physical co-clustering of two or more logical relations/tables in modern RDBMS
One possible approach to optimize search queries is (a) to store the records that retain data that corresponds to different relations/tables in (b) the same file → on the same pages. That way, a join ...
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How many concurrent sessions does Oracle database support?
I want to have an application linked to an Oracle database. The users will request data through the app, and the app will access the database and retrieve the info.
My question is: how many ...
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Least recently used replacement strategy - where is pin count stored?
I am reading a book on databases and a chapter in it talks about buffer manager and it's replacement strategies.
The two popular replacement startegies mentioned are least recently used - LRU and ...
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Direct database interaction with memory - how it works?
I am reading a book on databases and a chapter in it talks about buffer manager and it's replacement strategies.
I've noticed that the DBMS interacts directly with memory, as opposed to asking OS to ...
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is "create schema" the same way of saying "create database"?
I'm a beginner in DBMS, sorry if my question sounds dumb. I often see some textbooks says: create a schema . does it that mean "create a database"?
But isn't that a schema is also a skeleton of a ...
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102
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What DBMS to choose for my production environment? [closed]
This is my very first question on the StackExchange/StackOverflow community. I originally am an electrical engineer so I hope you bear with me.
I need to set up a database whose purpose is to be ...
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Oracle - stop dbms_service
I need to stop read-write service on standby so is there a way to lock connection within a specific service or to set a service as read-only?
Thanks in advance.
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View images as query results [closed]
I've done lots of research on the topic but I'm drawing a blank. Are their any database engines that can return rendered images in the query response?
For example:
Select images from fruit where ...
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Is there a place to store ERDs in Postgres?
Is there a designated spot in Postgres to store Entity-Relationship Diagrams (ERDs)?
I could just create a table with a BTYEA column or something, but I want to make sure to use what exists if ...
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SQL to MDX translation?
An MDX (a language dealing with multidimensional data, in particularly dealing with the cube metaphor) statement can be translated to an SQL (a well-known language for the relational model) statement -...
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Will Postgres handle the Unix Epoch problem?
I was wondering if Postgres will be handling the unix epoch problem coming in 2038? I have read about this and am wondering.
It's about a productivity thing obviously because it is so far away, but ...
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Error Code: 1239. Incorrect foreign key definition for 'foreign key without name': reference and table don't match
I'm making a new database in MySQL in which after making the Department table I receive an error when adding other tables.
CREATE TABLE Department (dept_name varchar(20), building varchar(15), budget ...
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Can a/some DBMS be installed as an OS [closed]
Is there any DBMS that can be installed as an OS instead of as an app on a OS?
I wasn't able to find any.
Later edit, just to clarify:
I'm used to installing a DBMS (MySQL, MSSQL) as a server(ice) ...
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1
answer
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Does the term "page" have the same meaning in DBMS and OS jargons?
I am learning the data format of DBMS and found we have a term: page.
Pages are the fetched data in main memory from external storage (eg. a disk, SSD) and several pages would be "cached" firstly ...
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57
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What does the DBMS do exactly when i send it a SELECT query regarding the .frm files and database pages? (MySQL)
so i was reading about database pages and DBMS in mysql and it got me really confused
so based on their documentation database pages have a part where it points to rows in the page, which have tuples ...
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1
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305
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How do graph databases differ from older navigational (hierarchical/network) databases?
I'm trying to improve my knowledge of graph databases, in particular DGraph. Are graph DBMSs just a new generation of pre-relational hierarchical/network model DBMSs, or is there something new at a ...
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Can independent applications cause roll back to each other's transactions?
I have a database built on SQL Server
Application-1 [Legacy App]:
Written in C#, and runs transactions on the above database.
Application-2 [New application being developed]:
Written in Python, ...
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Why does Antelope (a sensor-network DBMS) do an inverse select in order to remove tuples?
Antelope (a database management system [DBMS for brevity] which enables a sensor to act as a database server) claims that its remove operation is like a swap between two tables. It does an inverse ...
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Running two MySQL servers that use the same data directory
The situation
I have two MySQL instances, deployed on two different remote machines.
Both MySQL instances access the same data directory, which is stored on a persistent volume (this volume is ...
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views
Why do uncommitted transactions rollback instead of redo after a crash in ARIES?
Since all actions within a transaction are idempotent in crash recovery algorithms like ARIES that use write-ahead logging why do we rollback after a crash during an uncommitted transaction to get ...
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