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I. Introduction
Outline of SQL database language
SQL (short for Structured Query Language) is a powerful programming language intended for managing, querying, and manipulating relational databases. It offers a standard approach to communicating with databases allowing users to retrieve, insert, update, and delete data easily. SQL is popularly employed across different industries for data management and analysis due to its simplicity, versatility, and scalability.
Importance of SQL in data analytics
Database analytics become possible due to SQL’s role as a tool that extracts important findings from databases. It allows one to carry out complicated queries, aggregate data, join several tables and filter the data on defined criteria. Data analysis, report generation, data-driven decision-making, and predictive model building all hinge on SQL proficiency. Today, with the advent of a data-driven world, gaining proficiency in SQL is a sine-qua-non of any professional working in the field of data analytics or database management.
II.Understanding SQL Basics
What is SQL?
SQL is a domain language used to manage relational databases. It gives a set of commands and syntax rules for performing different operations like data querying, table structure modification, and user permission management. ANSI is the standardization body for SQL. Most DBMS use their implementation of SQL, for example, Oracle, SQL Server, PostgreSQL, and MySQL.
Basic SQL commands (SELECT, INSERT, UPDATE, DELETE)
SELECT: The SELECT statement is to get data from one or more tables in a database. It provides an option to define which columns are to be fetched and imposes filters or sorts over the output.
INSERT: The INSERT statement creates new rows of data in a table. It enables users to tell the values that they need to be loaded into each column of the table.
UPDATE: The UPDATE statement is for updating the data in a table. He enables the users to alter the values in selected columns in one or more rows according to certain conditions.
DELETE: The DELETE statement is intended for removing one or more rows from a table. It allows specifying conditions for filtering the rows to be deleted or to delete all rows from the table.
III. Retrieving Data with SQL
SELECT statement: Syntax and usage
The SELECT statement is the most commonly used SQL command for retrieving data from a database. Its basic syntax is:
SELECT column1, column2, ... FROM table_name WHERE condition;
- column1, column2, …: Columns to be retrieved from the table.
- table_name: Name of the table from which to retrieve data.
- condition: Optional criteria to filter the rows returned by the query.
IV.Filtering data with WHERE clause
The WHERE clause is used to specify conditions that must be met for a row to be included in the query results. It allows users to filter data based on specific criteria, such as comparing column values, using logical operators (AND, OR), and using SQL functions.
SELECT *
FROM employees
WHERE department = 'IT' AND salary > 50000;
This query retrieves all columns from the “employees” table where the department is ‘IT’ and the salary is greater than 50000.
