SELECT TABLE_ROWS
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'your_database_name'
AND TABLE_NAME = 'your_table_name';

CONCAT()

-- 모든 프로세스 조회
SHOW FULL PROCESSLIST;
-- 락테이블 조회
select * from information_schema.innodb_locks;
-- 대기중인 락 조회
select * from information_schema.innodb_lock_waits;
-- 트랜젝션조회
select * FROM information_schema.INNODB_TRX;

-- 해당 프로세스 종료
kill 495299;

-- 종합쿼리
SELECT * FROM information_schema.PROCESSLIST
WHERE Command <> 'Sleep'
AND USER NOT IN ('system user', 'event_scheduler')
ORDER BY TIME DESC
;

SELECT IFNULL ( null, 'no value');

DISTINCT

CREATE INDEX idx_order_date ON orders (order_date);

SHOW INDEX FROM 테이블_이름;