模糊查询:本质是比较运算符
运算符 | 语法 | 描述 |
---|---|---|
is null | a is null | 如果操作符为null,则结果为真 |
is not null | a is not null | 如果操作符不为null,则结果为真 |
between | a between b and c | 若a在b和c之间,则结果为真 |
like | a like b | SQL匹配,如果a匹配到b,则结果为真 |
in | a in(a1,a2,a3...) | 假设a在a1、a2、a3...其中的某一个值中,结果为真 |
-- ============================模糊查询==================================== -- like结合 % 或 _ -- % : 代表0到任意个字符 -- _ : 代表一个字符 -- 查询姓张的同学 select studentno,studentname from student where studentname like '张%'; -- 查询姓张的同学,名字后面只有一个字的 select studentno,studentname from student where studentname like '张_'; -- 查询姓张的同学,名字后面只有俩个字的 select studentno,studentname from student where studentname like '张__'; -- 查询名字中间带五的同学 where studentname like '%五%'; -- ============================in==================================== -- 查询 1001、1002、1003号学员 select studentno,studentname from student where studentno in (1001,1002,1003); -- 查询在北京的学生 -- select studentno,studentname from student where address in ('北京%'); in是具体的值,模糊查询只能和like使用 select studentno ,studentname from student where address in ('福建福州','北京朝阳'); -- ============================null \ not null=================================== -- 查询地址为空的学生 null '' select studentno ,studentname from student where address = '' or address is null; -- 查询有邮箱的同学 不为空 select studentno ,studentname,email from student where email is not null; -- 查询没有邮箱的同学 为空 select studentno ,studentname,email from student where email is null;
标签:studentname,studentno,19,查询,--,详解,操作符,null,where From: https://www.cnblogs.com/xusitu/p/17804121.html