SQL Tutorials

SQL Subquery: A Complete Guide

An SQL subquery is a query inside another query. It is used in the WHERE or HAVING clause of an SQL statement. Subqueries let you specify the results of one query as an argument in another query. When you’re writing…

SQL Aliases: A Complete Guide

An SQL alias is a reference name for a table or a column. They are used to shorten your queries if you have long table names. Both table and column aliases are defined using the AS keyword. An alias lasts…

SQL Left Join: A Complete Guide

An SQL LEFT JOIN is a type of SQL join. This join returns all the tables from a specified “left” column and the corresponding rows that match a particular condition in the “right” column. In many cases, when you’re writing…

SQL ORDER BY: A Complete Guide

The SQL ORDER BY statement determines the order in which records are returned by a query. You can return records in ascending or descending order by the value of any column in the table. Ordering query results makes it easier…

SQL INNER JOIN: A Complete Guide

The SQL INNER JOIN statement returns rows with exact values in two columns across two tables. You can join a table across one or multiple columns. JOIN statements connect two database tables and compare their contents. There may be times…

SQL Aggregate Functions: A Complete Guide

SQL aggregate functions retrieve information about the data in a database. You can use COUNT to find out how many records are in a database, for instance. Accepted aggregate functions are: COUNT, MIN, MAX, AVG, and SUM. There are occasions…

SQL Group By: A Complete Guide

The SQL GROUP BY statement appears in aggregate functions. It is used to collate the data you select from a query by a particular column. You can specify multiple columns which will be grouped using the GROUP BY statement. When…

SQL Like: A How-To Guide

The SQL LIKE operator uses wildcards to find data similar to a particular pattern. You can use an underscore to substitute for a single character or a percentage sign to substitute zero, one, or multiple characters. Have you ever wanted…

SQL Between: A Complete Guide

The SQL BETWEEN keyword retrieves values that fall within a particular set of values. It is often used to retrieve values between two dates or numbers. This keyword is used in WHERE clauses. The syntax for this keyword is: “BETWEEN…

SQL ALTER TABLE: A Guide

The SQL ALTER TABLE statement adds, changes, or removes a column in a table. This statement lets you modify a table after it has been created, even if the table stores records. You may decide that you need to make…

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