SQL Basics

• A record, also known as a row, represents each individual entry in a table. A record is a horizontal entity in a table.

• SQL keywords are not case-sensitive: select is the same as SELECT.

• A column is a vertical entity in a table that contains all information associated with a specific field.

• Most of the actions you need to perform on a database are done with SQL statements.

• SQL statements consist of keywords that are easy to understand.

• Some database systems require a semicolon at the end of each SQL statement.

  Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.

• How to put comments in SQL?

-- Any text between -- and the end of the line will be ignored (will not be executed

/*Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored. It is also used to just ignore a part of the statement */

Category	Type	Examples	Purpose
Operators	Arithmetic Operators	+, -, *, /, %	Perform mathematical calculations.
	Comparison Operators	=, !=, <, >, <=, >=	Compare values in queries.
	Logical Operators	AND, OR, NOT	Combine multiple conditions in WHERE.
	Bitwise Operators	&, `	, ^, ~, <<, >>`
	String Operators	`
	LIKE & Wildcards	LIKE, %, _	Pattern matching in text searches.
Statements	Data Query Language (DQL)	SELECT	Retrieve data from tables.
	Data Manipulation Language (DML)	INSERT, UPDATE, DELETE	Modify records in tables.
	Data Definition Language (DDL)	CREATE, ALTER, DROP, TRUNCATE	Define and modify database structures.
	Data Control Language (DCL)	GRANT, REVOKE	Manage permissions in the database.
	Transaction Control Language (TCL)	COMMIT, ROLLBACK, SAVEPOINT	Control transactions (ensuring consistency).
Clauses	Filtering Clauses	WHERE, HAVING	Filter records based on conditions.
	Sorting & Limiting	ORDER BY, LIMIT, TOP	Sort or limit the number of records.
	Grouping	GROUP BY	Aggregate data into groups.
	Join Clauses	INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN, SELF JOIN	Combine data from multiple tables.
	Subquery Clauses	EXISTS, IN, ANY, ALL	Use queries within queries.
	Set Operators	UNION, UNION ALL, INTERSECT, EXCEPT	Combine results from multiple queries.

Key Takeaways

Operators → Help perform calculations, comparisons, and logic in queries. Statements → Define what action is performed (SELECT, INSERT, etc.). Clauses → Modify the behavior of SQL statements (WHERE, ORDER BY, GROUP BY).