mysql 句法：

目录

mysql 句法：

交换sex的内容（m -> f, f -> m)

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交换sex的内容（m -> f, f -> m)

update salary set sex = (if(sex="m", "f", "m"));

update salary set sex = char(ascii('m') + ascii('f') - ascii(sex));

UPDATE salary SET sex = CASE sex WHEN 'm' THEN 'f' ELSE 'm' end;

update salary set sex = case sex when 'm' then 'f' when 'f' then 'm' end

 

查询同一特征的第一条数据

select sname from students where ssex = "男" group by ssex;

 

联合查询

select Sname, Sage, Ssex, sc.Cnum, score, Cname from student join sc on student.Snum = sc.Snum join course on course.Cnum = sc.Cnum;