## SQL history

SQL, which stands for Structured Query Language, is a programming language designed to manage and manipulate relational databases.

It provides a standardized way of interacting with databases, allowing users to perform various operations such as querying data, updating records, inserting new data, and deleting existing data.

SQL was developed in the early 1970s by IBM researchers Raymond Boyce and Donald Chamberlin. Initially, it was known as SEQUEL (Structured English Query Language). However, due to trademark issues, the name was later changed to SQL.

Comments in SQL:

Comments exist in all languages. However, Comments in SQL are non-executable statements that serve as documentation or explanatory notes within the code.

They are invaluable for enhancing code readability and understanding. In SQL, comments can be written using two different formats:

-- for single-line comments and /* */ for multi-line comments.

For example:

-- This is a single-line comment

/*
   This is a multi-line comment.
   It spans multiple lines for detailed explanations.
*/

ORDER BY Clause

The ORDER BY clause is used to sort the result set of a query based on specified columns in either ascending (ASC) or descending (DESC) order. It enables users to organize data according to their preferences, making it easier to analyze and interpret.

For example:

SELECT column1, column2
FROM table_name
ORDER BY column1 ASC;

<> (Not Equal To) Operator:

The <> operator, also known as the inequality operator, is used to compare two expressions for inequality. It returns true if the expressions are not equal and false if they are equal. This operator is handy for filtering data based on conditions where equality is not desired.

For example:

SELECT *
FROM table_name
WHERE column1 <> 'value';

= (Equal) Operator

The = operator is used to compare two expressions for equality. It returns true if the expressions are equal and false if they are not equal. This operator is commonly used in SQL for filtering data based on specific criteria.

For example:

SELECT *
FROM table_name
WHERE column1 = 'value';

Other Comparison Operators

SQL offers a variety of other comparison operators, including >, <, >=, and <=, which are used to compare values and expressions in different ways. These operators are crucial for building complex conditions in SQL queries.

AND Operator

The AND operator is a logical operator used to combine multiple conditions in a WHERE clause. It ensures that all conditions must be true for a row to be included in the result set. The AND operator allows for creating more specific and refined queries.

For example:

SELECT *
FROM table_name
WHERE condition1 AND condition2;

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