SQL

basic

SELECT * AS aliasNameFROM table
Where condition -- Selects after beeing grouped
GROUP BY column 
HAVING contition -- Selects before beeing grouped
ORDER BY column ASC/ DESC
LIMIT 30 -- only first 30 lines

/* Comment */

ASC is from small to big; A - Z (Default)

DESC is from big to small; Z - A

joins

SELECT * FROM table
JOIN otherTable ON t1.name = t2.name
Where condition
GROUP BY column 
ORDER BY column ASC/ DESC
LIMIT 30 -- only first 30 lines

SELECT OrderID, Quantity,
CASE
    WHEN Quantity > 30 THEN 'The quantity is greater than 30'
    WHEN Quantity = 30 THEN 'The quantity is 30'
    ELSE 'The quantity is under 30'
END AS QuantityText
FROM OrderDetails;

Methode
MIN()
MAX()
COUNT()
AVG()
SUM()

---

Wildcards

Symbol	Description
%	Represents zero or more characters
_	Represents a single character
[]	Represents any single character within the brackets
^	Represents any character not in the brackets
-	Represents any single character within the specified range

Example:

WHERE CustomerName LIKE 'a%'

Create

CREATE DATABASE databasename;
DROP DATABASE databasename;


CREATE TABLE Persons (
    PersonID int NOT NULL,
    LastName varchar(255) UNIQUE,
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255),
    PRIMARY KEY (PersonID),
    FOREIGN KEY (PersonID) REFERENCES ORDER(PersonID)
);
DROP TABLE table_name;


INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

DELETE FROM table_name WHERE condition;

---

Advanced

SELECT Count(*) AS DistinctCountries
FROM (SELECT DISTINCT Country FROM Customers);

SELECT column_name(s)
FROM table_name
WHERE EXISTS
(SELECT column_name FROM table_name WHERE condition);

SELECT column_name(s)
FROM table_name
WHERE column_name BETWEEN value1 AND value2;