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Effective Accelerationism

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SQL 101

Wed Apr 03 2024

Key SQL Categories

  • DDL (Data Definition Language): Commands that control the structure of a database and its objects.

    • CREATE: Creates databases, tables, indexes, etc.
    • ALTER: Modifies the structure of existing objects.
    • DROP: Deletes databases, tables, and other objects.
    • TRUNCATE: Quickly removes all data from a table.
  • DQL (Data Query Language): Commands for retrieving and filtering data from databases.

    • SELECT: Fetches data from one or more tables.
  • DML (Data Manipulation Language): Commands for changing data within tables.

    • INSERT: Adds new rows of data to a table.
    • UPDATE: Modifies existing data in a table.
    • DELETE: Removes rows from a table.
  • DCL (Data Control Language): Commands to manage database permissions and user access.

    • GRANT: Provides specific permissions to users.
    • REVOKE: Removes permissions from users.
  • TCL (Transaction Control Language): Commands for managing groups of SQL statements as a single unit (transactions).

    • COMMIT: Makes changes permanent in a database.
    • ROLLBACK: Reverts changes made during a transaction.
    • SAVEPOINT: Sets points within a transaction to potentially roll back to.


  • Arithmetic Operators: (+, -, *, /) for calculations.
  • Comparison Operators: (>, <, =, >=, <=, !=) for comparing values.
  • Logical Operators: (AND, OR, NOT) for combining conditions.
  • Other Operators:
    • LIKE: For pattern matching in strings.
    • IN: To check if a value exists within a set.
    • BETWEEN: To check if a value is within a range.


  • Aggregate Functions: Perform calculations on multiple rows, returning a single result:
    • COUNT()
    • MIN()
    • MAX()
    • AVG()
    • SUM()
  • String Functions: Manipulate text data:
    • UPPER()
    • LOWER()
    • CONCAT()
    • TRIM()
  • Date and Time Functions: Work with dates and times:
    • NOW()
    • CURDATE()
    • MONTH()
    • YEAR()
  • Other Functions: Conversion functions, mathematical functions, etc.

Data Types

(Data types can vary slightly between different database systems)

  • Numeric:
    • INT/INTEGER (whole numbers)
    • FLOAT/DECIMAL (numbers with decimal points)
  • String:
    • CHAR (fixed-length strings)
    • VARCHAR (variable-length strings)
    • TEXT (larger text fields)
  • Date and Time:
    • DATE
    • TIME
  • Boolean: (TRUE or FALSE)

How to Learn SQL

  1. Choose a Resource: There are many excellent options:
    • Online Courses: Platforms like Codecademy, Udemy, Coursera, Khan Academy.
    • Interactive Tutorials: W3Schools, SQLZoo, TutorialsPoint.
    • Books: Books tailored to your preference.
  2. Database Choice: Select a common database system to practice with:
    • MySQL
    • PostgreSQL
    • Microsoft SQL Server
    • SQLite
  3. Practice, Practice, Practice:
    • Find datasets online or create your own simple tables.
    • Run queries, experiment, and solidify your understanding.