SQL：加入LIKE和min（）

Question

我正在使用以下查询来获取与LIKE匹配的最低价格的行。

Suppliers 
id | name   
---------------------------------------- 
1 | sup1  
2 | sup2 

Prices 
id | article_number | price | supplier_id 
------------------------------------------------ 
1 | 12345678  | 312 | 1 
2 | 12345678  | 219 | 2 
3 | 87654321  | 312 | 1 


select prices.* from prices 
inner join 
( 
    select min(price) as price, 
    article_number as article_number from prices group by article_number 
) 
min_prices on prices.price = min_prices.price 
and prices.article_number = min_prices.article_number 

WHERE prices.article_number LIKE '".$q."%' 

虽然现在还希望获取来自供应商表的suppliers.name：

select prices.*, suppliers.name from prices, suppliers 
inner join 
( 
    select min(price) as price, 
    prices.article_number as article_number from prices group by prices.article_number 
) 
min_prices on price = min_prices.price 
and article_number = min_prices.article_number 

WHERE 
     prices.article_number LIKE '".$q."%' AND 
     prices.supplier_id = suppliers.id" 

这将返回行的18倍量的它应该是...？

此外，该表由10多百万行组成，因此效率非常重要。

Answer 1

对于性能，请在article_number上添加索引，并在子查询中使用prices.article_number LIKE '".$q."%'。你最好使用JOIN而不是,（这是旧的方式）来组合两个表。像这样：

select prices.*, suppliers.name 
from prices 
inner join ( 
    select min(price) as price, prices.article_number as article_number 
    from prices 
    where prices.article_number like '".$q."%' 
    group by prices.article_number 
) min_prices 
on price = min_prices.price 
and article_number = min_prices.article_number 
inner join suppliers 
on prices.supplier_id = suppliers.id 
where prices.article_number like '".$q."%'