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What is a relational database?

relational database (RDB) is a collective set of multiple data sets organized by tablesrecords and columns. RDBs establish a well-defined relationship between database tables. Tables communicate and share information, which facilitates data searchability, organization and reporting.

RDBs use Structured Query Language (SQL), which is a standard user application that provides an easy programming interface for database interaction.

Relational databases are based on the relational modelan intuitive, straightforward way of representing data in tables. In a relational database, each row in the table is a record with a unique ID called the key. The columns of the table hold attributes of the data, and each record usually has a value for each attribute, making it easy to establish the relationships among data points.

Benefits of Relational Databases:

  • Data Consistency
  • Commitment and Atomicity
  • Stored Procedures and Relational Databases
  • Database Locking and Concurrency

Relational Database Terms

Below are the unique terms and specific definitions that will help you understand what a RDB can do and how it works:

Row : A set of data constituting a single item.

For example, the data for a single employee (e.g. first name, last name, employee ID, hire date, work location, etc.) of a company would be displayed in a row. A row can also be called a record, an entity, or a tuple.

Column: Labels for elements of rows. A column gives context to the information contained in rows. For an employee database, the column headers could be the items listed above for employees. A column is also known as an attribute or a field.

Table: A group of rows that match the parameters set up for the table. The data in a table must all be related. An employee database may have separate tables for active employees, retired employees, and former employees. A table is also known as a relation or base revelar.

View: A set of data based on a query via the RDBMS; also known as result set or derived revelar.

Domain: The set of possible values for a given column. For example, the phone number and ZIP code columns would be numbers, while first and last names would be limited to letters.

Constraint: A narrowing of a domain. For example, the domain of the work location on a employee record would be alphanumeric, but it could be restricted to a predefined list rather than being a free-form field. The phone number field would be constrained to 10 digits.

Primary key: The unique identifier of a row in a table.

Foreign key: The unique identifier of a row in another table.

Distributed Database: A database that stores data in multiple locations, rather than on a single hard drive or server.

TYPES OF DATABASE RELATIONSHIPS

The power of a relational database is in the links and relations. By connecting rows in different tables through the use of primary and foreign keys, you can create views, reports, and other slices of information to serve your organization. There are three primary types of database relationships:

One-to-One: One row in one table is connected to one and only one row in another table. For example, a Social Security number is linked to a single employee.

One-to-Many: One row in one table is connected to zero, one, or more than one rows in another table. For example, one work location can be linked to many employees.

Many-to-Many: Zero, one, or many rows in one table are linked to zero, one, or many rows in another table. For example, multiple employees can be assigned to multiple projects.

What is Power BI ?

Kindly refer the below video on What is Power BI and it’s uses.

Power BI is a business analytics service by Microsoft. It is a cloud-based, elegant end-to-end business analytics tool that enables anyone to visualize, analyze, forecast any type of data with greater speed, efficiency, and understanding.

Power BI provides cloud-based BI services, known as “Power BI Services“, along with a desktop based interface, called “Power BI Desktop”. It offers data warehouse capabilities including data preparation, data discovery and interactive dashboards. Microsoft released an additional service called Power BI Embedded on its Azure cloud platform. One main differentiator of the product is the ability to load custom visualizations.

Key components:

Power BI Desktop : The Windows-desktop-based application for PCs and desktops, primarily for designing and publishing reports to the Service.

Power BI Service : The SaaS (software as a service) based online service (formerly known as Power BI for Office 365, now referred to as PowerBI.com or simply Power BI).

Power BI Mobile Apps : The Power BI Mobile apps for Android and iOS devices, as well as for Windows phones and tablets.

Power BI Gateway : Gateways used to sync external data in and out of Power BI. In Enterprise mode, can also be used by Flows and PowerApps in Office 365.

Power BI Embedded : Power BI REST API can be used to build dashboards and reports into the custom applications that serves Power BI users, as well as non-Power BI users.

Power BI Report Server : An On-Premises Power BI Reporting solution for companies that won’t or can’t store data in the cloud-based Power BI Service.

Power BI Visuals Marketplace : A marketplace of custom visuals and R-powered visuals

If you wish to learn Power BI, please find the necessary details from below link : https://sqlschool.com/PowerBI-Online-Training.html

This Power BI Online Training includes EVERY detail of each Power BI Visual, Usage and Properties as per the latest versions.

This Power BI course includes On-premise and Cloud Data Access, REST API, Azure Stream and R Integration including Data Modelling and ETL Techniques with Basic to Advanced Power Query (M Language), DAX Language Functions, Power BI Dashboards, Streaming Datasets, App Workspace, Content Packs, Data Gateways, Alerts, Power BI Report Server Components, Power BI Mobile Reports, Excel Integration, Excel Analysis, KPIs for Big Data Analytics, Microsoft OneDrive, Google Big Query, DataFlow and ETL in Cloud are also a part of this Power BI Online Training course in addition to Mock Interviews, Resume Guidance, Concept wise Interview FAQs and ONE Real-time Project.

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What is PL/SQL?

What is PL/SQL?

PL/SQL stands for Procedural Language extension of SQL.

PL/SQL is a combination of SQL along with the procedural features of programming languages.

It was developed by Oracle Corporation in the early 90’s to enhance the capabilities of SQL.

The PL/SQL Engine:

Oracle uses a PL/SQL engine to processes the PL/SQL statements. A PL/SQL language code can be stored in the client system (client-side) or in the database (server-side).

SQL GRANT REVOKE Commands

SQL GRANT REVOKE Commands

DCL commands are used to enforce database security in a multiple user database environment. Two types of DCL commands are GRANT and REVOKE. Only Database Administrator’s or owner’s of the database object can provide/remove privileges on a database object.

SQL GRANT Command

SQL GRANT is a command used to provide access or privileges on the database objects to the users.

The Syntax for the GRANT command is:

GRANT privilege_name
ON object_name
TO {user_name |PUBLIC |role_name}
[WITH GRANT OPTION];

  • privilege_name is the access right or privilege granted to the user. Some of the access rights are ALL, EXECUTE, and SELECT.
  • object_name is the name of an database object like TABLE, VIEW, STORED PROC and SEQUENCE.
  • user_name is the name of the user to whom an access right is being granted.
  • user_name is the name of the user to whom an access right is being granted.
  • PUBLIC is used to grant access rights to all users.
  • ROLES are a set of privileges grouped together.
  • WITH GRANT OPTION – allows a user to grant access rights to other users.

For Example:

GRANT SELECT ON employee TO user1;

This command grants a SELECT permission on employee table to user1.

You should use the WITH GRANT option carefully because for example if you GRANT SELECT privilege on employee table to user1 using the WITH GRANT option, then user1 can GRANT SELECT privilege on employee table to another user, such as user2 etc.

Later, if you REVOKE the SELECT privilege on employee from user1, still user2 will have SELECT privilege on employee table.

SQL LIKE Operator

The LIKE operator is used to list all rows in a table whose column values match a specified pattern. It is useful when you want to search rows to match a specific pattern, or when you do not know the entire value. For this purpose we use a wildcard character ‘%’.

For example: To select all the students whose name begins with ‘S’

SELECT first_name, last_name
FROM student_details
WHERE first_name LIKE ‘S%’;

The output would be similar to:

first_name          last_name
————-          ————-
Stephen                 Fleming
Shekar                   Gowda

The above select statement searches for all the rows where the first letter of the column first_name is ‘S’ and rest of the letters in the name can be any character.

What is a NULL Value?

A field with a NULL value is a field with no value.

If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field. Then, the field will be saved with a NULL value.

Note: It is very important to understand that a NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation!

What are the typical uses of service accounts in running SQL Server components?

Service accounts are all about security and access. So, for example, SQL Agent runs as a service and it can be configured (should be) to run under a service account. Let’s assume that you use Agent to run backups. Let’s also assume you backup to a shared file location on your network that’s not local to the machine you’re running SQL Agent on. You’ll need to ensure that the account configured for SQL Agent has access to that shared file location. While this may seem like work, what it in fact is doing is following the method of least access. That service account has to have access to that share, but it doesn’t need access to other file locations on your system, so you only give it what it needs and nothing more. Same thing applies to the other services and service accounts.

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How to Connect to SQL Server after Installation

This video explains on “How to Connect to SQL Server after Installation”

Applicable for SQL Server 2008, SQL Server 2008 R2, SQL Server 2012, SQL Server 2014 and SQL Server 2016

T0 resolve possible connection issues at basic level, ensure the following:

1. Verify and ensure correct server name is provided

2. Go to Run then services.msc then ensure SQL Server service for the respective instance is started.

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MS SQL Server – Editions

SQL Server is available in various editions. This chapter lists the multiple editions with its features.

Enterprise − This is the top-end edition with a full feature set.

Standard − This has less features than Enterprise, when there is no requirement of advanced features.

Workgroup − This is suitable for remote offices of a larger company.

Web − This is designed for web applications.

Developer − This is similar to Enterprise, but licensed to only one user for development, testing and demo. It can be easily upgraded to Enterprise without reinstallation.

Express − This is free entry level database. It can utilize only 1 CPU and 1 GB memory, the maximum size of the database is 10 GB.

Compact − This is free embedded database for mobile application development. The maximum size of the database is 4 GB.

Datacenter − The major change in new SQL Server 2008 R2 is Datacenter Edition. The Datacenter edition has no memory limitation and offers support for more than 25 instances.

Business Intelligence − Business Intelligence Edition is a new introduction in SQL Server 2012. This edition includes all the features in the Standard edition and support for advanced BI features such as Power View and PowerPivot, but it lacks support for advanced availability features like AlwaysOn Availability Groups and other online operations.

Enterprise Evaluation − The SQL Server Evaluation Edition is a great way to get a fully functional and free instance of SQL Server for learning and developing solutions. This edition has a built-in expiry of 6 months from the time that you install it.

2005 2008 2008 R2 2012 2014
Enterprise Yes Yes Yes Yes
Standard Yes Yes Yes Yes
Developer Yes Yes Yes Yes
Workgroup Yes Yes No No
Win Compact Edition – Mobile Yes Yes Yes Yes
Enterprise Evaluation Yes Yes Yes Yes
Express Yes Yes Yes Yes
Web Yes Yes Yes
Datacenter No No
Business Intelligence Yes

Using of And, OR and NOT in SQL Server

AND: The AND operator displays a record if all the conditions separated by AND is TRUE.

Syntax:

SELECT column1, column2, …
FROM table_name
WHERE condition1 AND condition2 AND condition3 …;

Example:

SELECT * FROM Customers
WHERE Country=’India’ AND City=’Hyderabad’;

The above SQL statement selects all fields from “Customers” where country is “India” AND city is “Hyderabad”

OR:The OR operator displays a record if any of the conditions separated by OR is TRUE.

Syntax:

SELECT column1, column2, …
FROM table_name
WHERE condition1 OR condition2 OR condition3 …;

Example:

SELECT * FROM Customers
WHERE City=’Hyderabad’ OR City=’Pune’;

The following SQL statement selects all fields from “Customers” where city is “Hyderabad” OR “Pune”

NOT:The NOT operator displays a record if the condition(s) is NOT TRUE.

Syntax:

SELECT column1, column2, …
FROM table_name
WHERE NOT condition;

Example:

SELECT * FROM Customers
WHERE NOT Country=’India’;