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SQL语句:
1.删除某个字段(如表名为aa字段名为jijie):delete from aa where jijie is null
2.select * from Student where CreatTime is null --字段creattime为空串这是判断条件
select * from Student where StudentProvinceID between 11 and 14 ---显示ID在11到14之间的所有记录
select * from Student where StudentProvinceID not in (11,12)--显示ID不是11或12的所有记录
select * from Student where StudentName like 'w%' --%代表任意个任意字符,即NAME为w开头的所有记录
select * from Student where StudentName like 'w____u'--下划线代表一个任意字符,命令中有四个,代表w u之间必须有四个字符
select * from Student where StudentBirth < '2010-01-01'
３.条件写法：1.(not)比较运算符引导的条件
2.is null is not null
3.(not) between and
4.(not) in
5.not like (%任意个字符 _任意单个字符)
6 and （or）
Region1