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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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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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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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, ...
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1answer
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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
113 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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Is there a way to automatically set triggers to update a field that is computed as an aggregation of other fields?

Let's say that I have these tables: user, task, and submission. A user can create a submission which will be scored by the system, which will assign a value to submission.score. Now, everytime a ...
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How to compare different DBMS? [closed]

I'm planning to compare MS SQL Server and Teradata. I know, they are have completely different architecture, because they were created to achieve different goals. But here we are. I have generated ...
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27 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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72 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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10 views

does overflow bucket addition happens manually or dynamically?

I am new to databases and I read in this tutorial that: The problem with static hashing is that it does not expand or shrink dynamically as the size of the database grows or shrinks. Dynamic ...
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1answer
64 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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42 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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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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1answer
2k 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 ...
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0answers
50 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
443 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
131 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
4k 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
306 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
960 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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1answer
2k 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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275 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 ...
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3answers
659 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. ...
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2answers
706 views

Independent pairs of RAID 1 is superior to RAID 10 [closed]

I am rather new to databases. I was reading up on RAID Storage and it seems that the consensus is that RAID 10 is RAID 10 is best is terms of performance and redundancy However at the end ...
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1answer
130 views

Performing projection first and then selection?

Consider a simple query: Select username,usertype from Table1 Where usertype='Manager' Most probably the DBMS will be performing selection first, and then projection i.e. first pulling out rows ...
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94 views

What does acid stand for in Database Management System? [closed]

I want to know about "acid" property in database management system. Can anyone explain me in brief?
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64 views

Access: search for more than one parameter?

I need to perform several queries, looking for more than one parameter. for example: in my field "lenght" I want to extract values matching both 4.6 and 4.7. then, next time I need 5.8 and 5.9, and ...
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2answers
1k views

FileWatcher Troubleshooting Options

I have setup a Credential/Procedure/Program/File Watcher/Job to monitor a folder for new files, but it is not working. I am trying to figure out what I can check to troubleshoot why this isn't ...