现有一个选修科目表SubjectRela
name | subject |
xiaoming | Math |
xiaoming | Chinese |
xiaoming | Endlish |
xiaohong | Math |
xiaohong | English |
Union:对两个结果集进行并集操作,不包括重复行,同时进行默认规则的排序;
Union All:对两个结果集进行并集操作,包括重复行,不进行排序;
Intersect:对两个结果集进行交集操作,不包括重复行,同时进行默认规则的排序;
场景1:获取既选修了Math,又选修了Chinese的学生name
select name from SubjectRela where subject='Math' Intersect select name from SubjectRela where subject='Chinese'
Minus:对两个结果集进行差操作,不包括重复行,同时进行默认规则的排序。
场景2:获取选修了Math,但是没选修Chinese的学生name
select name from SubjectRela where subject='Math' Minus select name from SubjectRela where subject='Chinese'