MySQL tips: SUM function sums according to conditions

1. Ordinary summation:

select sum(is_img)  is_img_sum from ec_assessment

2. Sum according to conditions:

select sum(if(is_img=1,1,0)) asis_img_sum from ec_assessment

白话注释：sum(如果is_img=1，那么就+1，否则就+0)

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Afterword: After I found out that my white shoes were dirty, my partner would brush me clean, so I decided to buy only white shoes from now on.