A schema of a database system is its structure described in a formal language supported by the database management system (DBMS) and refers to the organization of data to create a blueprint of how a database will be constructed (divided into database tables).

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Is doing an online alter on a MySQL table to add comments safe?

Is doing an online alter on a massive MySQL table to add or edit table or column 'comments' safe? Or do you need to take precautions like you would while adding, removing columns, etc on that table?
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Postgres: modify existing search_path (preserve current values)

Sometimes I would like to extend the existing search path, rather than replace it, say: To start with say it is already set like so: SET search_path TO schema_b, schema_c, public; I want to add my ...
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Improving performance of a weighted search query in SQLite3

For an intra-site search I have this table in an SQLite3 database, that relates ids to search terms with a certain weight: CREATE TABLE search_index ( id INTEGER(7) REFERENCES other_table, ...
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420 views

Which is the better schema design for a voting system?

Imagine a q/a site or forum similar to stackoverflow. I'm trying to determine which of these two methods would be the better design for a voting system: (note: I would also like to keep record of all ...
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105 views

Schema Design with “Seasonal” Data

I am developing a SaaS web application for School Management. What I need help is this: The whole application is purposed for the current year that the School is in. However, some data and ...
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Are there any tools to go from ERD to DB design and vice versa? [closed]

I'm learning DB design and looking for some tools, preferably open source software, that could help go from an ERD to a DATABASE and vice versa. For the record, the database i'm using is MySQL.
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103 views

How can I limit a user to only be able to run procs in a schema, which access another db?

In a SQL Server 2012 SP2 Standard Edition instance I have a user in database A that needs to be able to run stored procedures in schema foo within that database. They shouldn't be able to do anything ...
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63 views

Normilsation - 2NF and 3NF

I've been through several questions and youtube tutorials, i understand that 2NF is removing the partial dependencies and 3NF is the transitive ones, but i can't get my head around how the following ...
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1answer
226 views

Using the output from mysqldiff.exe to transform database2 to match database1

This question is related to another I had asked earlier here: Passing passwords more securely to mysql utilities on the command line. I have recently been trying to use mysqldiff.exe, part of MySQL ...
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2k views

How recording of every change of a row in a database is generaly stored?

In a project I'm working on, every change to the rows in some tables of the database must be tracked for further audit or rollback. It must be easy to find who modified the row, from which IP address ...
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215 views

db schema for a object with multiple foreign key tables

I have a question table which contains question_id, question_text and choice_type_id ( say freetext, binary choice and multiple choices ) Now, the question table (which has question_id, ...
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How to differentiate between class and attribute

I have this problem: Library has books, VDOs, CDs Journals. It gives loan to users. Books and Journals can be referential which cannot be loaned out more than 2hrs and non-referential which can be ...
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Tuple Relational Calculus help? [closed]

I have the following three questions in relation to the following diagram: 1) How many copies of the book titled “The Lost Tribe” are owned by the library branch whose name is "Sharpstown"? ...
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1answer
51 views

Why wouldn't I put the single preferred option into its own table, instead of having a 'Preferred' column?

In similar spirit to How to implement a 'default' flag that can only be set on a single row I would like to specify that, for any given list of possible names for a business, only one of the ...
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1answer
795 views

Is an ER diagram an example of a conceptual, logical or physical schema?

I have been reading databases, and I clearly understand the difference between a conceptual, logical and physical schema. An ER diagram is an example of which of these schema's?
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Is there any good tool for making Database Design and Prototypes? [closed]

I would like to have a good tool for designing the Database Schema with all the tables, columns, data types and relations. Today I mostly do this with pen and paper but I would like to do it in a good ...
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1answer
1k views

Select rows from table where each row refers to a different schema

I have customer table in public schema. And I have a schema named after each customer. Each customer schema contains different tables like portals, plugin, ... When I want to select portals used by ...
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2answers
212 views

Is EAV an appropriate design for a collection of coexisting metadata-rich “fact estimates” on objects? [closed]

I'm attempting to architect a system that will collect estimates on various quantities (10+) on each of many (300K+) objects, and make decisions from the historical record of these estimates. For ...
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26 views

CLR UDT SCH-M blocking

I’m hoping someone can provide some guidance on a problem I’m having with schema locking on C# CLR UDT’s. I’ve been on the Internet for an extended period of time researching my problem without ...
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742 views

Railway Reservation System [Miniature] Schema

I am working on designing a schema to support the development of a miniature railway reservation system, using oracle 11g XE. This is for a project purpose, I am need to be sure about the correctness ...
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1answer
798 views

Use a set database schema or EAV design? [duplicate]

I have already created a database design with a set schema. The database schema is for a web quotation form. PS it is not a simple quotation form and hence need to customise the form, form builders ...
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876 views

noSQL ACID and consistency for banking

We are building a real time banking platform and app. Our prime concern is safety and consistency of our data across multiple db servers. We need transactions and we can't afford to risk power ...
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Mongodb schema design validation

I am building an app which allows users to do some "tasks" to earn points. The "tasks" are part of a "campaign" which themselves are a part of "brands". I am confused about the schema for storing the ...
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1answer
393 views

How to efficiently create a new PRIMARY KEY CLUSTERED definition online

Given a table with a PRIMARY KEY definition (acting as the clustered index), I want to efficiently change the definition of the PRIMARY KEY (or at a minimum, just the clustered index) online. I would ...
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2answers
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Can we determine FDs if we are given some tuples?

I am taking a databases course and i'm learning about functional dependencies. I have searched around and did not find any information on this. My questions is if we are given a table with some ...
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1answer
445 views

Not able to solve issue: Incorrect string value: '\xC5\xABt\xC4\x97'

I am facing database error Incorrect string value: '\xC5\xABt\xC4\x97'. I did a lot search and tries a few ways, include move from utf8 to utf8mb4. But still not able to solve it. Following are the ...
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Is it bad idea to create foreign keys on the tables in a different schemas in the same database for big applications?

I am working on the transfer a big pl/sql web-based application to the dedicated server. This application is located in one schema with 70 packages of programm code. This application was made ...
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1answer
699 views

Should I save “document ID” as a String or Number in MongoDB

So I'm importing about a 100,000 documents into mondoDB. MongoDB already generates an Object hash but the data has a documentID that was used to identify records in the previous database. The IDs ...
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2answers
46 views

Is it a good idea to add a reserved field to a large MySQL table?

As you may know adding a new column to a MySQL table with millions of records is hard and in some cases impossible. Is it a good idea to add a text column to each table (say, meta) to save some ...
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1answer
751 views

Is there any way MySQL can list relationship cardinality between two entities?

I am working on the project where I have to analyse the MySQL schema. As a part of schema information, I want to list down relationship cardinality between different relations. Does MySQL stores ...
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1answer
245 views

Dropped connections, corrupted schema … is MySQL sick?

Lot's of problems and I wonder if it's all tracable to some root cause. I'm trying to load a simple schema related to product marketing. The symptoms are: Not being able to forward engineer said ...
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23 views

How to model role and different activities

I am new in the database design and I'm facing this problem, I hope somebody can help me. In my domain we have 3 roles, Non-Supervisor, Supervisor, Manager. I created a Person table and a role table ...
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Backup Only Database Schema Everynight

I have an instance with 15 databases on SQL Server 2012. I will set up to backup system which will work every night. I want to backup only the schema because several databases are very big. I haven't ...
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what is better, multiple column or multiple rows while schema design

I would like to know, which is best in fast retrieval and reporting as numbers of records will increase with time. So lower the record better would be the performance. Priority would be fast response ...
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1answer
416 views

How does Amazon create the RDS for Postgres? Some kind of Docker?

I am really curious about the infrastructure of Amazon. When I create a new instance of RDS, it gives me a host, username, password.. Everything. Behind the curtains, how do they do this? It´s some ...
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Percona and MariaDB-10.0 ignoring not null on table fields

On the percona-5.6 and MariaDB-10.0 servers, the NOT NULL declared on table field are being ignored. I am able to leave fields declared as NOT NULL empty when inserting data and the servers are not ...
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163 views

Convert multiple databases into schemas SQL Server

Due to a high amount of databases being created on my project and the rising cost per databases I had the following question: Is there a way to convert multiple databases in SQL Server into one ...
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828 views

Insert rows in a table, via a row-level trigger, activated after insertion in that same table

I have to design a schema and trigger system in SQL that will save words and their synonyms. I thought of this basic schema: create table words ( id int primary key auto_increment, word ...
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In terms of relational databases is a Relvar the equivalent to a Schema?

I've been reading up on relational databases and the term Relvar and schema keeps coming up. From my understanding: A relvar is a variable holding a relation. A schema is a logical definition of a ...
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178 views

Schemas and user permissions

When our custom, home-grown CMS creates data tables using the GUI, it creates them against the site-specific user schema (i.e. sitename) instead of the dbo schema. The issue is that our ...
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Is there a name for this database structure?

Noob question, sorry if it's too basic for this exchange. We process a routine data feed from a client who just refactored their database from a form that seems familiar (one row per entity, one ...
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1answer
49 views

Need Help in building database

I am developing an app that send messages (email and sms) to users. The db must also maintains the list of messages send to users. And also the status of messages send to user like send or failed. I ...
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1answer
130 views

Is there a performance hit by breaking out tables into different schemas in SQL Server?

Is there any kind of performance hit when querying by placing tables in different schemas in SQL Server. For instance if I had 2 tables, Table1 and Table2, and put Table1 into the test schema and ...
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1answer
61 views

Design for periodic data cuts

I've been building an application that has a 6-monthly update schedule, i.e. a cut of the data for H1 & H2 of each year. The previous version of this application implemented this by making a copy ...
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1answer
793 views

Migrating everything to do with a schema from one Oracle DB server to another

We have an old DB server, running Oracle 11g on Solaris. We also have a new DB server, also running Oracle 11g, but on RHEL. We want to move a schema to the new db - but we need everything it refers ...
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1answer
69 views

Schema copy from 9.5 V to 10.5

Using DB2 move utility db2move to copy schema and database from source to target server. The source server is Server1. The target server is Server2. Do I need to set up the TCP/IP port ...
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112 views

Schema for user drag and drop ordering

I'm trying to work out the schema for a system where users will be able to order items in an (unlimited length) list by drag and drop. Is there any kind of standard way of storing this ordering ...
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636 views

LCK_M_SCH_M Blocking

I have 2 stored procedures (one vendor, one third party) that are constantly (monthly) stepping on each other. They both (for some reason) acquire a schema lock when all they are doing is updating ...
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Accounting - Dimention table in mysql

I am designing a accounting and mini erp system. I use a date dimension table to track all date related data. In oracle we can have many schema for a database. so we could create each schema for ...
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1answer
105 views

ALTER TABLE blocking in MySQL 5.6

I have a question with a MySQL 5.6 master-slave setup. If I were to modify the master's schema with an ALTER TABLE SQL query, then when the slave tries to execute that ALTER TABLE statement too, would ...