SQL Lesson

In SQL, the UPDATE statement is used to modify existing data in a table. It allows you to update specific columns of one or multiple rows based on specified conditions. Basic Syntax The basic syntax of the INSERT statement is: UPDATE table_name SET column1 = value1, column2 = value2, … WHERE condition; table_name: Specifies the […]

In SQL, the INSERT statement is used to insert new records into a newly created table. It allows you to add data to specific columns in a table or insert data based on a query’s results. Here’s an overview of how to use the INSERT statement to insert data into tables. Basic Syntax The basic

The WHERE and HAVING clauses are both used to filter data in SQL queries, but they operate at different stages of query processing and have distinct purposes. It is important to understand their differences. Usage and Placement WHERE Clause: The WHERE clause is used to filter individual rows before grouping or aggregation occurs. It is

In SQL, the HAVING clause is used to filter grouped data based on conditions specified in the query. While the WHERE clause filters individual rows before grouping, the HAVING clause filters the result set after grouping has been applied. It allows you to apply conditions to the grouped data and retrieve only the groups that

In SQL, the GROUP BY clause is used to group rows based on one or more columns. It allows you to divide the result set into groups and apply aggregate functions to each group independently. The GROUP BY clause is often used in combination with aggregate functions to perform calculations on grouped data. Basic Syntax

Aggregate functions are powerful tools in SQL that allow you to perform calculations on sets of rows and return a single result. These functions, such as SUM, COUNT, AVG, MAX, and MIN, provide valuable insights into data by summarizing and analyzing information. Here’s an overview of how to use aggregate functions in SQL. SUM The

In SQL, table and column aliases are used to provide alternative names for tables and columns in a query. Aliasing can make the query more concise, improve readability, and can be especially useful when dealing with complex queries or when joining multiple tables. Aliasing Tables Table aliases provide a shorter or more meaningful name for

In SQL, JOIN operations are used to combine data from multiple tables based on related columns. There are different types of JOINs available to suit different requirements. Let’s explore the three common types of JOINs. INNER JOIN The INNER JOIN (or just JOIN) returns only the rows that have matching values in both tables being

In SQL, JOIN operations are used to combine data from multiple tables based on related columns. When we use JOIN, we actually use INNER JOIN, the most common type of join which returns only the rows that have matching values in both tables being joined. JOIN Syntax To JOIN two tables in order to combine

In relational databases, table relationships are established using primary keys and foreign keys. These concepts help maintain data integrity and establish connections between tables and allows you to combine data from multiple tables. Primary Key A primary key is a column or a combination of columns that uniquely identifies each row in a table. It