and–并且
or----或者
#查询多条件组合的例子,and 的优先级比or 高
select*from grade
…where sno=‘wn002’
…and sgrade>70
…or sno=‘wn008’;
select*from grade
…where sno=‘wn002’
…or sno=‘wn008’
…and sgrade>70;
#用于多个条件的拼接
1::selectfrom student where age=100 and sname =‘太上老君’;
2::seletfrom student where sname =‘猪八戒’ or sname=‘孙悟空’ and age =‘50’;-------同样牵扯到优先级