删除记录：
delete *
from table_name
解释：删除表中的所有数据
delete *
from table_name
where id<10
解释：删除表中id小于10的数据
delete *
from table_name1
where name
in(
select name
from table_name2 as b
where b.name like '%三%'
)
解释：从表2中筛选出name中包含‘三’的值，如‘张三’、‘王三’、‘李三’，表1删除name中含有这个三个值的记录。
in 关键字：范围筛选，where a in b，将a的值判断是否存在于b中
like 关键字： 模糊筛选
as 关键字：table_name as a，使用a即使用table_name