SQL began not too long ago in the distant path. It was developed in the 1970’s in an IBM lab in San Jose, California. The acronym “SQL” stands for Structured Query Language. This language was originally developed for IBM’s DB2 relational database management system (RDBMS). Currently the ISO and ANSI promote SQL standards. While most database systems implement the SQL standards, most have extensions that are not compatible with each other. However, the standard SQL language is generally universal. The most common SQL commands that you will encounter are SELECT, UPDATE, INSERT, and DELETE.
When working with data, you’ll find that you can group data into sets that appear a table structure, very similar to a typical spreadsheet. For instance, if you own a company and wanted to store data about various set, you would create tables for each of these sets such as customers, products, sales, etc… In each of these tables, you will have columns, or fields. For instance, in the customers table, you may define a customer number, customer name, customer address, and so on. In the customer table, each customer would fill a row of data. This row of data is called a record.
After you have stored this raw data, you may realize that this data can be related to each other. For instance, customers buy products. While customer data and product data is stored in different tables, you can relate them to each other through another table called Sales. The sales table would contain customer number and product number, and possible product quantity. To get a report on which products were sold to which customers, you would write a query to JOIN the various tables together. This joining allows you to keep the data separate without repetition of fields.
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