經過多個位置變量處理數據的小方法！

cat dd.txt

courseId  startTime  endTime

107 1548471600  1548475200
337 1550455200  1550458800
337 1553306400  1553310000

如上所述，如今有一批數據，須要經過courseId、startTime、endTime三個維度（三個變量）惟一肯定一條數據，而後以courseId分組進行數據統計。筆者記得有位置變量能夠實現，不過很遺憾的是忘記了，只能對而求其次，換了一種方法實現，若是有大神路過，還請留言指教

cat dd.sh
#!/bin/bash

username=account
passwd=mima
mysql -u$username -p$passwd -Bse "truncate table test.caidan"

while [ "1" = "1" ]
do
    id=`cat dd.txt | head -1 | awk '{print $1}'`
    start=`cat dd.txt | head -1 | awk '{print $2}'`
    end=`cat dd.txt | head -1 | awk '{print $3}'`
    num1=`mysql -u$username -p$passwd edusoho_e -Bse "SELECT COUNT(*) FROM course_member WHERE courseId=$id AND createdTime BETWEEN $start AND $end"`
    mysql -u$username -p$passwd -Bse "insert into test.caidan select $id,$num1"
    sed -i '1d' dd.txt
    num=`cat dd.txt | wc -l`
    if [ $num -eq 0 ];then
        exit
    fi
done

分組統計結果

SELECT id,SUM(num1) FROM `test`.`caidan` GROUP BY id ORDER BY NULL