25 lines
460 B
SQL
25 lines
460 B
SQL
-- 查询男生和女生各多少人
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SELECT sex,COUNT(*) FROM t_student GROUP BY sex;
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-- 查询男生和女生分别占总人数的比例
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SELECT
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sex,
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COUNT(*),
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CONCAT(ROUND(COUNT(*) * 100.0 / (SELECT COUNT(*) FROM tb_student), 2), '%') AS percentage
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FROM
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t_student
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GROUP BY
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sex;
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-- 查询每门课程下的学生总人数
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SELECT
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c.c_name,
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COUNT(*) AS student_number
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FROM
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stu_cou sc
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INNER JOIN t_course c ON sc.c_id = c.c_id
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GROUP BY
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c.c_name |