php - SQL query with multiple joins impacting performance -

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i have relational mysql database 4000 records. contacts table related both keywords , notes tables manny-to-many relationships. wrote query (with php) retrieve each contact record and, each contact, related notes , keywords in group concat function. if grab contacts, query performs relatively 2 left joins , group concat, takes 30 seconds. there way speed up?

here query: 

select  c.*, group_concat(distinct n.id, '[-]', n.value, '' separator '---') notes,         group_concat(distinct kk.id, '[-]', kk.value) keywords      contacts c     left join  notes n  on c.id n._contactid     left join           ( select  k.*, kc._contactid contactid              keywords k             inner join  keywords_contacts kc  on k.id kc._keywordid         ) kk  on kk.contactid c.id     group  c.id     order  c.`last name`, c.`first name`

i query can see c.id n._contactid, here making performace low use = operator , give index foreign key field _contactid.

same k.id kc._keywordid use = operator instead of , apply index on field _keywordid.


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