SQL 笔记1

IN 和 EXIST 区别

SELECT count(*) 
FROM Parts p1
WHERE NOT EXISTS 
(SELECT needsPart FROM Parts p2 WHERE p1.partNumber = p2.needsPart)

SELECT count(*) 
FROM Parts p1
WHERE p1.partNumber NOT IN 
(SELECT needsPart FROM Parts p2 WHERE p1.partNumber = p2.needsPart)

sth IN …