60 lines
869 B
SQL
60 lines
869 B
SQL
# 3.查询男生和女生各多少人。（15分）
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SELECT
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t_student.sex,
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COUNT( t_student.s_id )
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FROM
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t_student
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WHERE
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t_student.sex = '男'
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GROUP BY
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t_student.sex
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# 女生各多少人。（15分）
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SELECT
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t_student.sex,
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COUNT( t_student.s_id )
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FROM
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t_student
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WHERE
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t_student.sex = '女'
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GROUP BY
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t_student.sex
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SELECT
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COUNT(t_student.s_id )
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FROM
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t_student
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WHERE
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t_student.sex = '女'
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GROUP BY
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t_student.sex / (SELECT count(t_student.s_id) FROM t_student))
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SELECT count(t_student.s_id) FROM t_student AS coun /SELECT
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COUNT(t_student.s_id )
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FROM
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t_student
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WHERE
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t_student.sex = '男'
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GROUP BY
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t_student.sex
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# 5.查询每门课程下的学生总人数。（15分）
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SELECT t_course.c_name,COUNT(stu_cou.s_id) FROM stu_cou left join t_course ON t_course.c_id=stu_cou.c_id
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GROUP BY stu_cou. c_id
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