SQL Talk

What is Data?

Data is a collection of a distinct small unit of information. It can be used in a variety of forms like text, numbers, media, bytes, etc. it can be stored in pieces of paper or electronic memory, etc.

What is a Database?

What is a Relational Database?

A relational database is a type of database. It uses a structure that allows us to identify and access data in relation to another piece of data in the database. Often, data in a relational database is organized into tables.

It is called Relational Data Base Management System (RDBMS) because it is based on relational model introduced by E.F. Codd.

Tables: Rows and Columns

Tables can have hundreds, thousands, sometimes even millions of rows of data. These rows are often called records.

Tables can also have many columns of data. Columns are labeled with a descriptive name (say, age for example) and have a specific data type.

For example, a column called age may have a type of INTEGER (denoting the type of data it is meant to hold).

In the table above, there are three columns (name, age, and country).

The name and country columns store string data types, whereas age stores integer data types. The set of columns and data types make up the schema of this table.

The table also has four rows, or records, in it (one each for Natalia, Ned, Zenas, and Laura).

What is a Relational Database Management System (RDBMS)?

A relational database management system (RDBMS) is a program that allows you to create, update, and administer a relational database. Most relational database management systems use the SQL language to access the database.

What is SQL?

SQL (Structured Query Language) is a programming language used to communicate with data stored in a relational database management system. SQL syntax is similar to the English language, which makes it relatively easy to write, read, and interpret.

Many RDBMSs use SQL (and variations of SQL) to access the data in tables. For example, SQLite is a relational database management system. SQLite contains a minimal set of SQL commands (which are the same across all RDBMSs). Other RDBMSs may use other variants.

(SQL is often pronounced in one of two ways. You can pronounce it by speaking each letter individually like “S-Q-L”, or pronounce it using the word “sequel”.)

Popular RDBMS

SQL syntax may differ slightly depending on which RDBMS you are using. Here is a brief description of popular RDBMSs:

MySQL

MySQL is the most popular open source SQL database. It is typically used for web application development, and often accessed using PHP.

The main advantages of MySQL are that it is easy to use, inexpensive, reliable (has been around since 1995), and has a large community of developers who can help answer questions.

Some of the disadvantages are that it has been known to suffer from poor performance when scaling, open source development has lagged since Oracle has taken control of MySQL, and it does not include some advanced features that developers may be used to.

PostgreSQL

PostgreSQL is an open source SQL database that is not controlled by any corporation. It is typically used for web application development.

PostgreSQL shares many of the same advantages of MySQL. It is easy to use, inexpensive, reliable and has a large community of developers. It also provides some additional features such as foreign key support without requiring complex configuration.

The main disadvantage of PostgreSQL is that it can be slower in performance than other databases such as MySQL. It is also slightly less popular than MySQL.

Oracle DB

Oracle Corporation owns Oracle Database, and the code is not open sourced.

Oracle DB is for large applications, particularly in the banking industry. Most of the world’s top banks run Oracle applications because Oracle offers a powerful combination of technology and comprehensive, pre-integrated business applications, including essential functionality built specifically for banks.

The main disadvantage of using Oracle is that it is not free to use like its open source competitors and can be quite expensive.

SQL Server

Microsoft owns SQL Server. Like Oracle DB, the code is close sourced.

Large enterprise applications mostly use SQL Server.

Microsoft offers a free entry-level version called Express but can become very expensive as you scale your application.

SQLite

SQLite is a popular open source SQL database. It can store an entire database in a single file. One of the most significant advantages this provides is that all of the data can be stored locally without having to connect your database to a server.

SQLite is a popular choice for databases in cellphones, PDAs, MP3 players, set-top boxes, and other electronic gadgets.

 Problem Statement:-

OUTPUT:

 

Table and Insert SQL Script :

 Problem Statement :

OUTPUT :

 Problem Statement :

Given below table Emp as Input which has two columns 'Group' and 'Sequence'. Write a SQL query to find the maximum and minimum values of continuous ‘Sequence’ in each ‘Group’

INPUT:

Table and Insert SQL Script : CREATE TABLE Emp( [Group] varchar(20), [Sequence] int ) INSERT INTO Emp VALUES('A',1) INSERT INTO Emp VALUES('A',2) INSERT INTO Emp VALUES('A',3) INSERT INTO Emp VALUES('A',5) INSERT INTO Emp VALUES('A',6) INSERT INTO Emp VALUES('A',8) INSERT INTO Emp VALUES('A',9) INSERT INTO Emp VALUES('B',11) INSERT INTO Emp VALUES('C',1) INSERT INTO Emp VALUES('C',2) INSERT INTO Emp VALUES('C',3)

Solution 1:

; WITH DetailData as( SELECT [Group], [Sequence], ROW_NUMBER() OVER(PARTITION BY [GROUP] ORDER BY [Sequence]) as RN, [Sequence]- ROW_NUMBER() OVER(PARTITION BY [GROUP] ORDER BY [Sequence]) as Group_Split FROM Emp ) SELECT [Group], MIN([Sequence]) as Min_Sequence, MAX([Sequence]) as Max_Sequence FROM DetailData GROUP BY [Group], Group_Split ORDER BY [Group];

 Problem Statement:-

EXPECTED OUTPUT:

Table and Insert Script _____________________________________________ CREATE TABLE [dbo].[Transaction_Tbl]( [CustID] [int] , [TranID] [int] , [TranAmt] [float] , [TranDate] [date] ) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1001, 20001, 10000, CAST('2020-04-25' AS Date)) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1001, 20002, 15000, CAST('2020-04-25' AS Date)) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1001, 20003, 80000, CAST('2020-04-25' AS Date)) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1001, 20004, 20000, CAST('2020-04-25' AS Date)) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1002, 30001, 7000, CAST('2020-04-25' AS Date)) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1002, 30002, 15000, CAST('2020-04-25' AS Date)) INSERT [dbo].[Transaction_Tbl] ([CustID], [TranID], [TranAmt], [TranDate]) VALUES (1002, 30003, 22000, CAST('2020-04-25' AS Date))