(SQL Example for Citizen Data Scientist & Business Analyst) SQL | WITH clause The SQL WITH clause was introduced by Oracle in the Oracle 9i release 2 database. The SQL WITH clause allows you to give a sub-query block a name (a process also called sub-query refactoring), which can be referenced in several places within …
SQL for Citizen Data Scientist in 2 Weeks – SQL SELECT Statement.
(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 values SUM() …
(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 used by …
(SQL Tutorials for Citizen Data Scientist) SQL Temporary Tables In this tutorial you will learn how to create temporary tables using SQL. Creating Temporary Tables A temporary table is a table that is visible only to the current session, and is dropped automatically when the session in which it was created is closed. Since temporary tables …
(SQL Tutorials for Citizen Data Scientist) SQL Cloning Tables In this tutorial you will learn how to create a duplicate copy of an existing table. Cloning or Copying a Table There may be a situation when you just want to create an exact copy or clone of an existing table to test or perform something without affecting …
(SQL Tutorials for Citizen Data Scientist) SQL Dates and Times In this tutorial you will learn how to work with dates and times in SQL. Date and Time Manipulation Along with strings and numbers, you often need to store date and/or time values in a database, such as an user’s birth date, employee’s hiring date, date of the …
(SQL Tutorials for Citizen Data Scientist) SQL CREATE INDEX Statement In this tutorial you will learn how to create indexes on tables to improve the database performance. What is Index? An index is a data structure associated with a table that provides fast access to rows in a table based on the values in one or more …
(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. Instead, it …
(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. To understand …