SQL 中DISTmCT是怎么用的

我有一个题目是：假设供应商S和供应情况SPJ的关系模式分别为S（Sno,Sname,Status,City）和SPJ（Sno,Pno,Jno,Qty）。SQL查询“零件号Pno等于P3”的供应商名Sname:
SELECT DISTmCT Sname
FROMS
WHERE 0<
(SELECT COUNT(*)
FROM SPJ)WHERE S.Sno=SPJ.Sno
AND SPJ.Pno=‘P3’

帮忙分析哈红色的部分是什么意思啊

DISTmCT 应该是 distinct

查询“零件号Pno等于P3”的供应商名Sname应该是

select distinct S.Sname from S inner join SPJ on S.Sno=SPJ.Sno where SPJ.Pno='P3'

或者这样也可以

select S.Sname from S where exists(select 1 from SPJ where SPJ.Sno = S.Sno and Pno='P3')