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Introduction to SQL
Introduction to SQL in Big Data Analytics
- SQL(Structured Query Langauge) is a query language to work with a database
- It is globally employed language works in mining data from various data sources which includes big data technologies and data warehouse
- SQL is employed with R. Its like SQL in a database
- The key elements of SQL are select, from and where
- To work with SQL inside R, install sqldf package like represented below
- The select query is employed to get the values of columns from tables and to perform calculations
- The underlying code explains select query various forms. In that ej1 highlights simple select query and the ej2 develops new variables
- An another important query statement in SQL is group by
- It permits to calculate a numerical value for various groups of an another variable
The underlying code highlights the demo on group by query statement
- Joins are another important query statement in SQL. It performs joining multiple tables
- There are various categories of joins existing which includes inner join outer join, etc.,
- Join merges 2 or more table into a single table through 1 common column matching values in 2 or more the tables
- The underlying code highlights the joining operations namely inner join and left outer join
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