MYSQL CASE WHEN the index-CodePudding

Function is the sales statistics yesterday, today's sales
To the query conditions where the value is different, different execution plan,

Article 1 data number is 0, 0 data article number is 72 the entire table is 77 data

Instead of less than records query type is ref
For the record are ALL

Establish index below

 
Explain the SELECT 
COALESCE (sum (CASE WHEN mo. Pay_status=0 THEN mo. Actual_amount END), 0) AS 'todayAmount, 
COALESCE (sum (CASE WHEN mo. Pay_status=0 THEN mo. Actual_amount END), 0) AS 'yesterdayAmount, 
COALESCE (sum (CASE WHEN mo. Pay_status=0 THEN mo. Actual_amount END), 0) AS 'totalAmout' 
The FROM 
Mall_order mo 
WHERE 
Mo. Tenant_group_code='1'