#运算符:
# 逻辑运算符 and, or, not !
# 比较运算:>,>=,<,<=, =,!=
# 范围:in, between and
# 查询分数为88 和 90的记录
select * from t_score where score = 88 or score=90;
select * from t_score where score != 90;
# 查询分数最高的前3个同学:使用降序,再用limit取前3条数据。
select score from t_score order by score desc limit 3;