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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.

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View images as query results [on hold]

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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1answer
25 views

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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1answer
13 views

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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1answer
53 views

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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1answer
77 views

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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0answers
26 views

Steps for write ahead log protocol

What are the steps for write ahead log protocol? I know these are the steps, but I don't know the order they occur in. a. Updated data is persisted on disk. b. Data is updated in memory. c. The ...
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2answers
59 views

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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1answer
83 views

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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1answer
37 views

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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1answer
50 views

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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2answers
74 views

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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0answers
25 views

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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2answers
512 views

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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2answers
86 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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1answer
60 views

need sql to represent relation negation and date compare problem

I have the following tables: Employee(eid,ename,salary,did,classification) Project(pid,pname,did,budget,ddate) Department(did,dname,floor,head) dbudget(did,byear,budget) Project(pid,pname,did,budget,...
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1answer
45 views

problem with selecting correct values from database [closed]

I have the following database and I'm having problems writing the correct select phrase. I am new to SQL and hope you could help me by showing me the correct way to select the desired data: Employee (...
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1answer
1k views

Most suitable database design for multi store inventory? [closed]

I am trying to understand how to manage multiple stores in a inventory management system (Each store has large number of data). There are 123 stores in this shop. Some stores have sub stores. So I ...
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1answer
73 views

Postgresql extension pageinspect - mean bt_metap

I am using Postgresql extension pageinspect. Could someone tell me the meaning of these columns: magic, version, root, level, fastroot, fastlevel of the bt_metap function. This information is not ...
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0answers
113 views

DBMS Query Preprocessor Checks Semantics or Syntax?

I encountered the following statement when reading about the constituents of a query processor in a DBMS: ... (b) A query preprocessor, which performs semantic checks on the query (e.g., making ...
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1answer
22 views

_Batch_ priorities in PostgreSQL

I would want to tag many queries and mostly materialised view refreshing tasks as low priority in my RDBMS, in the fashion I run the web browser on the local machine as low priority (because JS, CSS, ...
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0answers
109 views

Understanding multivalued dependencies

This is my first time studying multivalued dependencies and there is a question that was posted by my lecturer as a class exercise. I have an answer, but I'm not 100% sure it was right. Please let me ...
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0answers
49 views

Logical data independence

I have a basic doubt about logical data independence. I read that in logical independence, we can remove attributes from relation without affecting external schema. How can the removal of attribute ...
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6answers
12k views

My professor taught me that `COUNT` doesn't count duplicates

At university, my professor taught me this year that this SQL statement: SELECT COUNT(length) FROM product will return 2 with the following dataset: | product | |id | length | code | |----...
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0answers
369 views

Function can't drop synonym

I am debugging an application that is working correctly on many PCs but not on one particular one. The part of the application that is having an issue is an automated restore using dpimp from another ...
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1answer
593 views

When is the SGA created in an Oracle database environment? [closed]

When is the SGA created in an Oracle database environment? A.) When the database is created B.) When a user process is started C.) When the database is mounted D.) When the instance is started E.)...
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2answers
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How to implement many-to-many relation between three table?

I have these tables StudentInfo: subjectId(primary key) name location SubjectInfo: subjectId(primary key) subjectName totalmarks TeacherInfo: teacherId(primary key) teacherName ...
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1answer
112 views

Connecting to a Data Virtualization Tool from an oracle database?

I have this following data of DVT(Vertica) o DSN Name,Host,Port,Username,Password,Domain,Datasource. How can I create a DB link using those credentials of a DVT from an oracle database?what query I ...
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1answer
247 views

Concatenate fields in access

How come my statement is getting marked wrong? The question is: Create a query based on the tblCustomer and tblPurchase tables that will concatenate the member’s first and last names (separated by a ...
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1answer
107 views

CHECK constraint not implemented in MySQL, what about other DBMS? [closed]

MariaDB, which is based on MySQL, does not. Oracle, including Oracle XE 10g and 11g do. I'm curious as to other DBMS?
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2answers
107 views

Why are there so many definitions of database?

In my lecture today, I heard that a database is a collection of related data that is organized. From Google I came across these: "A database is a collection of data, typically describing the ...
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2answers
4k views

How to Add AFTER Delete Trigger in My case?

I am Making a Database Management System of Hospital in MySQL WorkBench, and i Want to Make a After Delete Trigger in my case. The scenario is i have two Tables 1) The Patients which are currently ...
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0answers
60 views

problem with column oriented dbms features

I am currently looking for a free(or at least low cost) column oriented DBMS with really good compression abilities (at least 10:1 ratio) and fast response time. Having evaluated multiple open source ...
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1answer
239 views

Grouping operator in DBMS (γ) is duplicate-impervious. Why?

I'm reading Database Systems by Ullman where its mentioned that γ is duplicate-impervious. I don't understand why a simple group operation should cause elimination of duplicates. Aliter, Duplicate-...
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1answer
44 views

can we call CRUD operations as service methods?

I was asked this question by one of my superiors. The usual operations we do on database table from Service layer in java is Create, Update, Retrieve, Delete. These operations are basically services, ...
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3answers
17k views

Oracle 11gR2: ORA-01102: cannot mount database in EXCLUSIVE mode

I am running Oracle 11gR2 on an AIX box. I did a rename database and change DB ID using NID. I can restart db in a nomount mode, but I can not mount it by the following error. ORA-01102: cannot ...
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0answers
105 views

How to bucketize using Query optimal bucketization algorithm

I am trying to implement query optimal bucketization algorithm (QOB). The input of the algorithm is D=(V,F) where V is the value of the attribute and F is the frequency of occurrence. For EXAMPLE D = ...
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2answers
951 views

PL/SQL block running without printing any output

I'm trying to exexcute a pl/sql block using dbms_output to obtain a console output but without reason the unique answer by SQL developer is 'Anonymous block finished'. declare v_count integer; ...
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1answer
370 views

Tables for two type of users in database. How to solve this problem?

This is the Entity Relationship Diagram I have created for my web application (based on Oracle APEX project). Two type of users can sign up and login and each user has his/her own profile and ...
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1answer
47 views

A form including content from two tables

I am working to create a database of all the places or administrative entities of one country. Most work will be about adding new districts. I have to detail which region every district belongs to. ...
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0answers
78 views

Type of relational/object-oriented database with improved joins for object graphs?

I would like to know if there is a specific name or term for the kind of database described below: I notice one of the biggest problems when working with relational databases and object trees/graphs ...
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2answers
13k views

Copying CSV file to temp table with dynamic number of columns?

I am wondering if there is a way to copy a csv file into a temp table where the number of columns is unknown in the csv file. The DB software I'm using is PgAdmin III. I figured out that if I do know ...
2
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0answers
331 views

Method to Obtain LossLess Join BCNF Decomposition

I have been told a way to obtain loss less join BCNF but I don't know how to calculate candidate keys(also called super key in some cases) and trivial Dependency. I have been given a relation R = (...
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2answers
2k views

Oracle SQL Creating Copy of Table Using DBMS_metadata

so I am trying to create a copy of a table using dbms_metadata. I know you can get the DDL of a table by executing DBMS_METADATA.get_DDL('Table','TABLENAME') so my question now is how can I use this ...
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1answer
174 views

Clarification for database creation and relations

I've trying to make database with few tables and relations between them. As I'm not very good in databases at all I need some clarifications. The idea is to connect table with table_1, table_2 and ...
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2answers
5k views

Performance Benchmark - MySQL vs PostgreSQL [closed]

this is my first question here in DBA. I wish to do a performance comparison between MySQL and PostgreSQL using same database on the basis of total time taken to parse + execute + send result back ...
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1answer
972 views

Decompose Relation R(ABCDE) in 2nf and 3nf

Given relation R(ABCDE) with functional dependencies A->C B->D AB->E Given: AB is the primary key. I know that this relation is in 1NF because of partial dependencies A->C and B->D Now how I ...
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3answers
3k views

Does 3NF require 2NF?

I am a bit confused with the definition of 3NF. According to Wikipedia: The third normal form (3NF) is a normal form used in database normalization. 3NF was originally defined by E.F. Codd in ...
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3answers
11k views

What is the difference between covering and overlapping constraints use in DBMS?

What is the difference between covering and overlapping constraints use in DBMS?
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1answer
913 views

How to drop table with all reference to this table

I want to drop a table, and this table has be many table's foreign key. So I want to drop all those reference (just refernece, not other table) within the drop table process. Is there any simple SQL,...
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3answers
2k views

What is the best way to store a lot of user-encrypted data?

I'm about to develop an application that will mainly store user-encrypted data. Each piece of data being encrypted thanks to an AES key, itself encrypted with the public RSA key of each granted user. ...