Tag Archives: SQL tutorials

Beginners Guide to SQL – SQL Functions

Hits: 14 (SQL Tutorials for Citizen Data Scientist) SQL Functions SQL has many built-in functions that enable you to perform calculations on data. SQL Aggregate Functions SQL aggregate functions perform calculation on a set of values and return a single value. The following table summarizes some useful aggregate functions: Function Description AVG() Returns the average of …

Beginners Guide to SQL – SQL Subqueries

Hits: 17 (SQL Tutorials for Citizen Data Scientist) SQL Subqueries In this tutorial you will learn how to embed a query within another query in SQL. What Is a Subquery? A subquery, also known as a nested query or subselect, is a SELECT query embedded within the WHERE or HAVING clause of another SQL query. The data returned by the subquery is …

Beginners Guide to SQL – SQL CREATE VIEW Statement

Hits: 9 (SQL Tutorials for Citizen Data Scientist) SQL CREATE VIEW Statement In this tutorial you will learn how to create, update, and delete a view using SQL. Creating Views to Simplify Table Access A view is a virtual table whose definition is stored in the database. But, unlike tables, views do not actually contain any data. …

Beginners Guide to SQL – SQL HAVING Clause

Hits: 20 (SQL Tutorials for Citizen Data Scientist) SQL HAVING Clause In this tutorial you will learn how to filter the groups returned by a GROUP BY clause. Filtering the Groups Based on Condition The HAVING clause is typically used with the GROUP BY clause to specify a filter condition for a group or an aggregate. The HAVING clause can only be used with the SELECT statement. …

Beginners Guide to SQL – SQL GROUP BY Clause

Hits: 8 (SQL Tutorials for Citizen Data Scientist) SQL GROUP BY Clause In this tutorial you will learn how to group rows based on column values. Grouping Rows The GROUP BY clause is used in conjunction with the SELECT statement and aggregate functions to group rows together by common column values To understand this easily, let’s look at the following employees and departments tables. +——–+————–+————+———+ | emp_id …

Beginners Guide to SQL – SQL ALTER TABLE Statement

Hits: 3 (SQL Tutorials for Citizen Data Scientist) SQL ALTER TABLE Statement In this tutorial you will learn how to alter or modify an existing table using SQL. Modifying Existing Tables It is quite possible that after creating a table, as you start using it, you may discover you’ve forgot to mention any column or constraint or …

Beginners Guide to SQL – SQL LIKE Operator

Hits: 10 (SQL Tutorials for Citizen Data Scientist) SQL LIKE Operator In this tutorial you will learn how to retrieve the data based on a partial match. Pattern Matching So far, you’ve seen the conditions that identify an exact string, e.g. WHERE name=’Lois Lane’. But in SQL you can perform partial or pattern matching too using the LIKE operator. The LIKE operator …

Beginners Guide to SQL – SQL UNION Operation

Hits: 41 (SQL Tutorials for Citizen Data Scientist) SQL UNION Operation In this tutorial you will learn how to combine the results of two or more SQL queries. The UNION Operator The UNION operator is used to combine the results of two or more SELECT queries into a single result set. The union operation is different from using joins that combine …