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Editorial Team
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Asked: 2026-05-22T14:20:04+00:00

Right I have no idea why but this query takes well over 6 seconds

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Right I have no idea why but this query takes well over 6 seconds to execute, index’s are all setup correctly and if I run each query separately it works great with less than 0.5 seconds to execute.

Here is the query

SELECT c.supplier_id, supplier_name, address1, address2, address3, address4, suppliertype, postcode, contact_name,
(SELECT COUNT(*)
    FROM supplier_questions q1
    WHERE c.supplier_id = q1.supplier_id AND q1.incomplete = '0') AS questions, 
IF (active=1,'Yes', IF (active=2, 'NCR Only','Inactive')) AS rated, 
(SELECT COUNT(*)
    FROM supplier_questions q2
    WHERE c.supplier_id = q2.supplier_id AND q2.reviewed = '1') AS reviewed, 
questapproved, 
ss.supplier_no AS supplier_no
FROM suppliers c
INNER JOIN supplier_site ss ON c.supplier_id = ss.supplier_id
WHERE c.supplier_id != '0' AND ss.site_id = '2'
GROUP BY c.supplier_id
ORDER BY c.supplier_name ASC
LIMIT 0, 20

Results of the Explain query is as follows 

id  select_type table   type    possible_keys   key key_len ref rows    Extra
1   PRIMARY ss  ref site_id,supplier_id site_id 4   const   1287    Using where; Using temporary; Using filesort
1   PRIMARY c   eq_ref  PRIMARY PRIMARY 4   ss.supplier_id  1   
3   DEPENDENT SUBQUERY  q2  ref supplier_id,reviewed    reviewed    4   const   263 Using where
2   DEPENDENT SUBQUERY  q1  ref supplier_id,incomplete  incomplete  4   const   254 Using where

The reason the count queries are in there is because I need to know the number of rows from those tables, this can’t be done in another query as the results also need to be sorted by those values 🙁

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1 Answer

  1. Editorial Team

    As a stab in the dark, does this run faster? (I havent got a mysql to verify the syntax on, so forgive any slight mistakes, but you might get the idea)

    SELECT c.supplier_id, supplier_name, address1, address2, address3, address4, suppliertype, postcode, contact_name, questions, reviewed 
IF (active=1,'Yes', IF (active=2, 'NCR Only','Inactive')) AS rated,  
questapproved,  ss.supplier_no AS supplier_no 
FROM suppliers c 
INNER JOIN supplier_site ss ON c.supplier_id = ss.supplier_id 
inner join 
(SELECT supplier_id, sum(if(incomplete='0',1,0)) as questions,  sum(if(incomplete='1',1,0)) as reviewed FROM supplier_questions q1 group by supplier_id) as tmp
on c.supplier_id = tmp.supplier_id
WHERE c.supplier_id != '0' AND ss.site_id = '2' 
GROUP BY c.supplier_id 
ORDER BY c.supplier_name ASC LIMIT 0, 20
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