Questions tagged [schema]

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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300
votes
4answers
567k views

How do I list all schemas in PostgreSQL?

When using PostgreSQL v9.1, how do I list all of the schemas using SQL? I was expecting something along the lines of: SELECT something FROM pg_blah;
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8answers
229k views

Difference between database vs user vs schema

I'm really confused with the terms database, user and schema. Can anyone explain how they are different from each other (if they are)? If they are same then, what are the similarities between them? ...
70
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5answers
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Is there a name for this database schema of key values?

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 column per attribute) to one that seems unfamiliar to me (one ...
68
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5answers
11k views

How can a group track database schema changes?

What version control methodologies help teams of people track database schema changes?
48
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1answer
23k views

Best practices for schema changes and data migrations to a live database without downtime?

How do you make schema changes to a live database without downtime? For instance, lets say I have a PostgreSQL database with a table including various user data like email addresses etc, all ...
47
votes
3answers
78k views

ERROR: no schema has been selected to create in

I am working on an amazon RDS postgresql database where I know there had been some issue with the public schema (maybe it was dropped). But apparently the schema exists, and anyway the problem is not ...
34
votes
7answers
139k views

Copy complete structure of a table

Using some methods, when you create a copy of a table you lose indexes, PK, FK, etc. For example in SQL Server I can say: select * into dbo.table2 from dbo.table1; This is just a simple copy of the ...
32
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4answers
30k views

Should dbo schema be avoided?

When it comes to the dbo schema: Is it a best practice to avoid using the dbo schema when creating database objects? Why should the dbo schema be avoided or should it? Which database user should own ...
29
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2answers
170k views

How to transfer data using expdp and impdp commands?

I'm an Oracle noob, and my intention is to transfer all data and metadata from one schema to another schema within an Oracle database. I'm planning to use datapump's expdp and impdp commands. I have ...
26
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3answers
17k views

What are some best practices for using schemas in SQL Server?

I understand the capabilities of SQL Server Schemas, but what are the best practices? Sure they give another layer of security, and provide logical grouping of database objects within the database, ...
25
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17answers
64k views

How can I compare the schema of two databases?

Is there a way to find the differences in two SQL Server databases (schema only). One is local and the second is at a customer's site. We are experiencing problems with crystal reports running some ...
25
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2answers
27k views

Difference between Owned Schemas and Role Membership for Microsoft SQL Server

Are there differences between Owned Schemas and Role Members? From my understanding, the Role Members are compulsory - user need to have at least one of the check box under Role Members checked. ...
23
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2answers
2k views

Decision criteria on when to use a non-dbo schema vs a new Database

I'm mostly an application developer but find myself having to do all the up-front database work for my current project (btw... its MS SQL Server 2008). As a first decision, I'm trying to figure out ...
22
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6answers
25k views

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 ...
21
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7answers
50k views

Query to compare the structure of two tables in MySQL

To automate the backup process of one of my MySQL databases, I would like to compare the structure of two tables (current version vs old version). Can you think of a query that can compare two tables?...
21
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4answers
31k views

Is there a tool to check if my database is normalized to the third normal form?

I learned about normalization recently, and understand how important it is when implementing a new schema. How can I check if my database is 2NF or 3NF compliant ? Manual review is a sure option, ...
17
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4answers
29k views

List primary keys for all tables - Postgresql

Is there a query that will do that? I found some queries that can do this for one table, but I wasn't able to modify it so I can see: tablename | column | type
17
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5answers
16k views

Finding empty columns of a table in PostgreSQL

What query would return the name of the columns of a table where all rows are NULL?
17
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6answers
4k views

Redgate SQL Compare vs Visual Studio 2010 Premium/Ultimate database project

I currently use the Visual Studio Professional Edition which has the database project as a project template, but some of its features are not available, for example Schema Compare tool. The schema ...
16
votes
1answer
38k views

How to transfer the ownership of the dbo schema in SQL Server 2012

I've accidentally given a user the ownership of the db_owner schema (using the check box in the UI as below) and now I cannot: Transfer ownership to another user Drop the user from DB (though I can ...
16
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2answers
10k views

PostgreSQL: schema diff/patch tool [closed]

Consider the following setting: A production DB A dev db, on which schema changes are made to enable new features When the development of a new feature is complete, I have to manually update the ...
16
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3answers
43k views

Schema design for products with multiple variants/attributes?

I'm using MySQL. The idea is similar to shopify with a different concept, so users are going to add their own products with multiple types of variants and attributes. From all the research I've done ...
15
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2answers
2k views

Schema-less/flexible + ACID Database?

I am looking at rewriting a VB based on-premise (locally installed) application (invoicing+inventory) as a web based Clojure application for small enterprise customers. I am intending this to be ...
15
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2answers
29k views

Why can't I see my table (PostgreSQL) when I use \dt(+) inside psql?

I have created the table donor in the schema reference as per: CREATE TABLE reference.donor ( donor_code smallint PRIMARY KEY, donor_name character varying NOT NULL, donor_type smallint ...
14
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5answers
33k views

PostgreSQL: Creation date of a table

I've recently finished a project, during which many DB tables were created. Most of these tables contain temporary garbage, and I am looking for a simple way to list all these tables. Is there a ...
14
votes
1answer
29k views

PostgreSQL complaining about shared memory, but shared memory seems to be OK

I've been performing kind of intensive schema dropping and creating over a PostgreSQL server, but now complains..: WARNING: out of shared memory ERROR: out of shared memory HINT: You might need to ...
14
votes
3answers
9k views

Is there an Open Source Metadata Management Solution? [closed]

Is there an Open Source Metadata Management Solution? I'd like to create a Metadata Repository that will hold the details of the metadata of database schemas, tables and data items of hundreds of ...
13
votes
5answers
6k views

eCommerce orders table. Save prices, or use an audit/history table?

Im designing my first eCommerce schema. I've been reading around the subject for a little while, and am a bit confused about the relationship between an order_line_item and a product A product can ...
13
votes
5answers
6k views

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 ...
12
votes
2answers
34k views

Allow user to do anything within his own schema but not create or drop the schema itself

I have created a schema in SQL Azure and granted the following permissions to a database role: CREATE ROLE myrole AUTHORIZATION dbo; EXEC sp_addrolemember 'myrole', 'myuser'; CREATE SCHEMA myschema ...
12
votes
3answers
493 views

How-to implement an entity with an unknown maximum number of attributes?

I am designing a baseball simulation program and I have run into a problem with designing the boxscore schema. The problem I have is that I want to track how many runs are scored in each inning. The ...
12
votes
2answers
5k views

SSDT Schema Compare fails when comparing my DB Project to my Azure Server

I have a SQL Database project that I have built our enterprise DB on. It has deployed several times on internal and AWS hosted SQL servers using SSDT's Schema Compare tool. The problem when I post ...
12
votes
2answers
74k views

Error 42P01: relation does not exist

I'm new at creating databases, and this error has me dumbfounded, as I am super new with DB admin things (I mostly do reporting type queries). I created a new database through pgAdmin3 GUI, and I'm ...
11
votes
3answers
50k views

SQL Server: grant select access to a user in a view and not in its tables

I have a SQL Server 2012 instance with a few databases. In one of them I created a view, that selects tables in more than a database. I want a user to be able to select that view, but it must not ...
11
votes
3answers
8k views

Schema Migration: SQL Server Data Tools vs Liquibase and Flyway

This might seem like a stupid question, but I've been looking into open source solutions for schema migration, namely Liquibase and Flyway. However, my boss told me that SQL Server Data Tools (SSDT) ...
11
votes
2answers
5k views

Do schema changes “break” Availability Groups or are they handled transparently?

My organization is planning to adopt SQL Server 2012 Availability Groups and I am trying to understand what impact (if any) it will have on our application upgrade process. We release application ...
11
votes
3answers
14k views

Slot Time Challenge - Doctor Appointment database schema

I am trying to make a doctor appointment system where patient online will have two options: First time visit (this visit should be 20 mins) Follow up visit (this visit should be 10 mins) Constraints:...
10
votes
3answers
2k views

What are the consequences of not specifying NOT NULL in PostgreSQL for fields which can't be null?

I have an application (data is stored in PostgreSQL), where majority of the fields in the tables are always not null, but the schema for these tables does not enforce this. For example look at this ...
10
votes
2answers
957 views

Can I losslessly decompose this table?

I've stumbled across a database design problem that's out of my league, and my go-to DBA guru is off on fire drills. In essence, I have a table with the following primary key (PK for brevity): ...
10
votes
3answers
4k 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 ...
9
votes
4answers
4k views

How to version control PostgreSQL schema with comments?

I version control most of my work with Git: code, documentation, system configuration. I am able to do that because all my valuable work is stored as text files. I have also been writing and dealing ...
9
votes
2answers
11k views

Which datatype to store XML data in: VARCHAR(MAX) or XML

I am defining a schema for a new set of resources using SQL Server 2008... In this case, each record (e.g. row) will need to store XML fragments. From time-to-time; although not frequently; I'll need ...
9
votes
1answer
2k views

Efficiently storing sets of key-value pairs with wildly different keys

I inherited an application that associates many different types of activities with a site. There are roughly 100 different activity types, and each one has differing set of 3-10 fields. However, all ...
9
votes
2answers
1k views

Find rows where integer sequence contains a given subsequence

Problem Note: I refer to the mathematical sequences, not the sequences mechanism of PostgreSQL. I have a table representing sequences of integers. The definition is: CREATE TABLE sequences ( id ...
9
votes
1answer
5k views

Pros and cons of using many schemas in PostgreSQL as opposed to just one?

For a large SAAS application (backed by PostgreSql 9.4), with over 300,000 accounts (and growing), what are the pros and cons of using a schema per account to partition the data vs putting all the ...
9
votes
1answer
855 views

Designing Simple Schema for Disaggregation of Demand Forecast

I am doing a simple database design task as a training exercise where I have to come up with a basic schema design for the following case: I have a parent-child hierarchy of products (example, Raw ...
8
votes
4answers
1k views

Guidance for using composite keys to identify rows

Is it good practice (or would it have any adverse effects) to use a set of 4 columns to identify a row as being unique (one being a foriegn key, the other three being float data types)? I'm attempting ...
8
votes
1answer
3k views

How does Postgres 9.2's streaming replication handle schema changes, and initial table setup?

I want to set up a backup database on the physical server which sits right under my primary physical database server. I'm using Postgres 9.2, and I want to use synchronous, streaming replication (for ...
8
votes
2answers
40k views

How can extract the table schema from just the .frm file?

I have extracted the data directory of mysql from a backup and need to get the schema from an old table, however it's a backup from a different machine. I have read a fair number of tutorials today ...
8
votes
1answer
1k views

Concept of Schema in PostgreSQL

I am not able to understand concept and usage of schema in PostgreSQL. I have no idea how it can affect my database design. Why should I use it? Can it affect me in future if I decide to not think ...

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