优化查询（MySQL）

Question

I have this tables in MYSQL:

products(prodId, Hide)
cat_binds(prodId,SptPath)
params(paramId,prodId,langId,value)

Query

SELECT 
        DISTINCT(params.value) 
FROM 
        products,
        cat_binds, 
        params 
WHERE 
        products.prodId = params.prodId 
        AND 
        params.paramId =  '1' 
        AND 
        params.langId =  '1' 
        AND 
        products.prodId = cat_binds.prodId 
        AND 
        cat_binds.SptPath LIKE '-2147483644\_%' 
        AND 
        products.Hide = '0'

How optimizing this query? How create right indexes which generate less rows wanted for result.

Thanks for help

Answer 1

Use joins instead of cartisians which fetch undesired rows.

SELECT DISTINCT
  (params.value)
FROM products
  LEFT JOIN cat_binds
    ON cat_binds.prodId = products.prodId
  LEFT JOIN params
    ON params.prodId = products.prodId
WHERE params.paramId = '1'
    AND params.langId = '1'
    AND cat_binds.SptPath LIKE '-2147483644\_%'
    AND products.Hide = '0'

Answer 2

Your SQL looks good and if you have added the Primary Index on all the IDs fields i think it will fine . MySQL will also optimized internally to make the order correct . I have only concern about the WHERE condition containing LIKE expression. As you are using the '%' condition in the last I think adding Index to this column will be helpful but if you put '%' in front then index will have not much effect