SQL Not Equal 가이드

value1 <> value2
value1 != value2

SELECT 5 <> 3;
-- Output: true

SELECT 'apple' != 'apple';
-- Output: false

SELECT NULL <> 3;
-- Output: NULL

-- MySQL and SQLite show true and false as 1 and 0. SQL Server can't
-- select a comparison like this: use it in a WHERE clause there.

-- Input: tickets
-- id | subject               | status
-- ---+-----------------------+--------
-- 1  | Login fails on Safari | open
-- 2  | Typo on pricing page  | closed
-- 3  | Export times out      | pending
-- 4  | Add a dark theme      | NULL

SELECT id, subject, status
FROM tickets
WHERE status <> 'closed';

-- Output:
-- id | subject               | status
-- ---+-----------------------+--------
-- 1  | Login fails on Safari | open
-- 3  | Export times out      | pending

-- Input: the tickets table above

SELECT id, subject, status
FROM tickets
WHERE status <> 'closed' OR status IS NULL;

-- Output:
-- id | subject               | status
-- ---+-----------------------+--------
-- 1  | Login fails on Safari | open
-- 3  | Export times out      | pending
-- 4  | Add a dark theme      | NULL

-- Input: the tickets table above

SELECT id, status FROM tickets WHERE status NOT IN ('closed', 'pending');

-- Output:
-- id | status
-- ---+-------
-- 1  | open

SELECT id, status FROM tickets WHERE status NOT IN ('closed', NULL);

-- Output:
-- id | status
-- ---+-------
-- (0 rows)

-- Input: the tickets table above

SELECT id, status FROM tickets WHERE status IS DISTINCT FROM 'closed';

-- Output:
-- id | status
-- ---+--------
-- 1  | open
-- 3  | pending
-- 4  | NULL

-- MySQL has no IS DISTINCT FROM. Use its NULL-safe <=> instead:
SELECT id, status FROM tickets WHERE NOT (status <=> 'closed');

-- Input: invoices
-- invoice_id | customer   | status | amount
-- -----------+------------+--------+--------
-- 1001       | Acme Corp  | paid   | 1200.00
-- 1002       | Birch & Co | void   | 450.00
-- 1003       | Acme Corp  | open   | 300.00
-- 1004       | Cobalt Ltd | paid   | 875.50

SELECT SUM(amount) AS invoiced
FROM invoices
WHERE status <> 'void';
-- Output: 2375.50

-- Input: articles
-- id | title                | topic
-- ---+----------------------+-------
-- 1  | Indexing basics      | SQL
-- 2  | Your first JOIN      | SQL
-- 3  | Docker for beginners | DevOps
-- 4  | Window functions     | SQL

SELECT id, title
FROM articles
WHERE topic = 'SQL'
  AND id <> 2;

-- Output:
-- id | title
-- ---+-----------------
-- 1  | Indexing basics
-- 4  | Window functions

-- Input: products
-- product_name   | category     | price | stock_quantity
-- ---------------+--------------+-------+---------------
-- Desk Organizer | Office       | 18.50 | 40
-- Fax Machine    | Discontinued | 89.00 | 3
-- Gift Wrap      | Seasonal     | 0.00  | 120
-- Trail Backpack | Outdoors     | 64.00 | 0
-- Water Bottle   | Outdoors     | 12.99 | 75

SELECT product_name, category, price
FROM products
WHERE category <> 'Discontinued'
  AND price > 0
  AND stock_quantity <> 0;

-- Output:
-- product_name   | category | price
-- ---------------+----------+------
-- Desk Organizer | Office   | 18.50
-- Water Bottle   | Outdoors | 12.99

-- Input: audit_log
-- log_id | field_name | old_value   | new_value
-- -------+------------+-------------+------------
-- 1      | email      | dan@old.com | dan@new.com
-- 2      | city       | Austin      | Austin
-- 3      | plan       | free        | pro

SELECT log_id, field_name, old_value, new_value
FROM audit_log
WHERE old_value <> new_value;

-- Output:
-- log_id | field_name | old_value   | new_value
-- -------+------------+-------------+------------
-- 1      | email      | dan@old.com | dan@new.com
-- 3      | plan       | free        | pro

-- Input: invitations
-- guest       | email            | rsvp
-- ------------+------------------+------
-- Ines Moreau | ines@example.com | yes
-- Raj Patel   | raj@example.com  | no
-- Hana Sato   | hana@example.com | NULL
-- Leo Grant   | leo@example.com  | maybe

SELECT guest, email, rsvp
FROM invitations
WHERE rsvp <> 'yes' OR rsvp IS NULL;

-- Output:
-- guest     | email            | rsvp
-- ----------+------------------+------
-- Raj Patel | raj@example.com  | no
-- Hana Sato | hana@example.com | NULL
-- Leo Grant | leo@example.com  | maybe