What is SQL, and why should I care; or, An exercise in herding cats

A Brief History

Why should I care?

Photo by ETA+ on Unsplash

Digging a little deeper


1. Data Definition Language (DDL)

CREATE — — — — — Create a table or database

ALTER — — — — — — Modify values in tables

DROP — — — — — — Delete a table from a database

2. Data Manipulation Language (DML)

INSERT — — — — — Insert new rows in a table

UPDATE — — — — — Update values of existing rows in a table

DELETE — — — — — Delete a row or entire table

3. Data Control Language (DCL)

GRANT — — — — — Provide easy access to users

REVOKE — — — — Take back access privileges from users

4. Transaction Control Language (TCL)

COMMIT — — — — Deploy/apply /save changes in the database

ROLLBACK — — — Cancel/undo changes made in the database

SAVEPOINT — — — Temporarily save data in the database

5. Data Query Language (DQL)

SELECT — — — — — Fetch data from tables/database

Please help me find Kitty

Step 1: Create kitty table

name TEXT,
color TEXT,
neighborhood TEXT,
birthday INTEGER

Step 2: Add Kitty

INSERT INTO cats (name, color, neighborhood, birthday) VALUES 
('Kitty', 'white', 'London suburbs', 1101);

Step 3: Look at our data!


Step 4: Cats named Kitty!

SELECT * FROM cats WHERE name = "Kitty";

Step 4: AND

SELECT * FROM cats WHERE name = "Kitty" 
AND color = "white";

Step 5: ORDER BY

SELECT * FROM cats WHERE name = "Kitty"
AND color = "white"
ORDER BY birthday DESC;

In summary




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