SQLCheatSheet

Basic Query Structure

SELECT column1, column2, ...  
FROM table_name  
WHERE condition1 AND/OR condition2  
ORDER BY column1 [ASC/DESC], column2 [ASC/DESC] ;  

Filtering Data

AND: Both conditions must be true.  
SQL  
WHERE country = 'USA' AND region = 'West'  
OR: At least one condition must be true.  
SQL  
WHERE state = 'CA' OR state = 'OR'  
BETWEEN: Filter values within a range (inclusive).  
SQL  
WHERE salary BETWEEN 50000 AND 80000  
LIKE: Pattern matching with wildcards.  
%: Matches zero or more characters. (city LIKE 'New%')  
_: Matches a single character. (phone LIKE '_12-3456')  
IN: Check against a list of values  
SQL  
WHERE job_title IN ('Manager', 'Analyst', 'Developer')  

Operators

= Equal to  
<> or != Not equal to  
> Greater than  
< Less than  
>= Greater than or equal to  
<= Less than or equal to  

Joins

INNER JOIN: Return rows with matching values in both tables.  
SQL  
SELECT *  
FROM employees  
INNER JOIN departments ON employees.dept_id = departments.dept_id;  
LEFT JOIN: Return all rows from the left table, matching rows from the right where possible.  
SQL  
SELECT *  
FROM customers  
LEFT JOIN orders ON customers.customer_id = orders.customer_id;  
RIGHT JOIN: Return all rows from the right table, matching rows from the left where possible (similar to LEFT JOIN, but tables are reversed).  
FULL OUTER JOIN: Return all rows from both tables, matching where possible.  

Aggregate Functions

AVG(column): Calculate the average of a column.  
COUNT(column): Count the number of non-null values in a column.  
COUNT(*): Count the number of rows.  
MIN(column): Find the minimum value in a column.  
MAX(column): Find the maximum value in a column.  
SUM(column): Calculate the sum of values in a column.