-- How many total sectors are there?

SELECT 
    COUNT(*) AS total_sectors
FROM sectors;

SELECT * FROM sectors;

-- List all sectors where sector_id are 1, 2 and 3.

SELECT
    *
FROM sectors
WHERE
    id_sector IN (1,2,3)

-- List all sectors where sector_id are NOT 1, 2 and 3.

SELECT
*
FROM sectors
WHERE
    id_sector NOT IN (1,2,3)