Question

Is it possible to optimise this query ?

SELECT 
    tr.transferfrom, tr.transferto, br.id as 'BR_ID',tr.refno, 
    br.name as 'BR_NAME', br.code as 'BRANCH_CODE', tr.docno, tr.transdate,
    stk.stockno,stk.salescat,tr.qty, tr.sprice,tr.qty*tr.sprice as 'GROSS_SALES' 
FROM 
    TRANSFER tr 
JOIN 
    branch br on tr.branchid = br.id 
JOIN 
    stocks stk on tr.stockid=stk.id 
WHERE 
    RIGHT(tr.refno,7) = 'ST00576' AND LEFT(tr.refno,2) = 89 
    AND stk.stockno = 'NS4370 CR - L'; 

Answer 1

1. Create index for tr.refno and replace LEFT(tr.refno,2) = 89 with tr.refno LIKE '89%'
2. Create composite index stk.id + stk.stockno
3. Make sure br.id is covered by index
4. If there are really a lot of records (hundreds of millions) and this query if performed often – may be it makes sense to store last 7 tr.refno chars in separate field to avoid RIGHT(tr.refno,7) = 'ST00576' (not sure if sql server supports reverse indexes)