MySQL 查询花费太长时间才能完成

Question

我正在使用 MySQL 数据库和以下查询:

SELECT
    customer_id,
    customer_code, 
    customer_name,  
    customer_address,
    customer_home_town
FROM  
    customers
    INNER JOIN (
        SELECT 
            issue_entry_customer_id,
            SUM(issue_entry_copies
              +issue_entry_subscribe
              +issue_entry_freecopies) AS col_copies 
        FROM 
            issue_entry 
        WHERE 
            issue_entry_deleted_status = 0  AND
            DATE_FORMAT(issue_entry_date,'%Y-%m') 
                = '".dateDatabaseFormat($issue_date)."'     
        GROUP BY 
            issue_entry_customer_id
    ) col_table 
        ON issue_entry_customer_id = customer_id
            AND customer_code = 1
            AND col_table.col_copies != 0
    ORDER BY
        customer_id ASC

issue_entry 表包含超过 500 000 行。

如何提高性能？

Answer 1

table_name alias INNER JOIN table_name2 alias ON ... 

这就是 INNER JOIN 查询的原理。为什么要在 INNER JOIN 语句之后进行选择？