【数据库】一个题目

"求至少用了供应商“S1”所供应的全部零件的工程号"的两种解法

https://blog.csdn.net/weixin_43461724/article/details/108884823

这个问题存在歧义，博主的是一种理解，我的理解是选择的工程严格地用了供应商“S1”所供应的全部零件，且这些零件不是由其他供应商供应的。

SELECT DISTINCT JNO

FROM

(

SELECT JNO

FROM SPJ

WHERE SNO = 'S1'

) AS SPJ1

WHERE NOT EXISTS

(

SELECT *

FROM

(SELECT PNO

FROM SPJ

WHERE SNO = 'S1') AS SPJ2

WHERE SPJ2.PNO NOT IN

(

SELECT PNO

FROM

(SELECT PNO,JNO

FROM SPJ

WHERE SNO = 'S1') AS SPJ3

WHERE SPJ3.JNO = SPJ1.JNO

)

)