MySQL按年龄段查询

<?php

//全镇教师年龄分布，1为男，0为女

$sqljs = "select  
sum(case when xingbie='男' then 1 else 0 end) as '男教师总人数',
sum(case when xingbie='女' then 1 else 0 end) as '女教师总人数',
sum(case when xingbie='男'  and nianling >0 and nianling <30 then 1 else 0 end) as '男30以下',
sum(case when xingbie='女'  and nianling >0 and nianling <30 then 1 else 0 end) as '女30以下',
sum(case when xingbie='男'  and nianling >=30 and nianling <40 then 1 else 0 end) as '男30-40',
sum(case when xingbie='女'  and nianling >=30 and nianling <40 then 1 else 0 end) as '女30-40',
sum(case when xingbie='男'  and nianling >=40 and nianling <50 then 1 else 0 end) as '男40-50',
sum(case when xingbie='女'  and nianling >=40 and nianling <50 then 1 else 0 end) as '女40-50',
sum(case when xingbie='男'  and nianling >=50 then 1 else 0 end) as '男50以上',
sum(case when xingbie='女'  and nianling >=50 then 1 else 0 end) as '女50以上'
from  teacher  where zaizhi='是';";
$resultjs = mysqli_query($conn, $sqljs);
$rowsjs = mysqli_fetch_row($resultjs); 
//释放结果集
mysqli_free_result($resultjs);//教师男女年龄分布
    //6.关闭数据库资源
    mysqli_close($conn);

?>