LIMIT clause

-- Specifying a limit on the number of records that will be displayed
SELECT column_name 
FROM table_name 
LIMIT 5;
                                    

COUNT function

-- Counting records in a table
SELECT COUNT(*)
FROM table_name; 
                                    

SUM function

-- Summing up values
SELECT SUM(column_name)
FROM table_name; 
                                    

AVG function

-- Calculating the average value
SELECT AVG(column_name)
FROM table_name; 
                                    

MAX function

-- Finding the highest value
SELECT MAX(column_name)
FROM table_name; 
                                    

MIN function

-- Finding the lowest value
SELECT MIN(column_name)
FROM table_name; 
                                    

ROUND function

-- Rounding a given value to a certain number of decimal places
SELECT column2_name, ROUND(column2_name, 2)
FROM table_name; 
                                    

GROUP BY clause

-- Grouping records by the values of a specified column
SELECT column_name, COUNT(*)
FROM table_name
GROUP BY column_name;
                                    

Column references

Referring to columns by their order in the SELECT clause.

1 - column1_name

2 - column2_name

SELECT column1_name, column2_name
FROM table_name
GROUP BY 2
ORDER BY 1;
                                    

HAVING clause

-- Adding a condition to the GROUP BY clause
SELECT column_name, COUNT(*)
FROM table_name
GROUP BY column_name
HAVING COUNT(*) < 3;