我正在尝试将典型的“购买'x'并购买'y''功能的客户添加到我的网站上。这是表结构：
Table: qb_invoice
+--------------------------------+------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------------------------+------------------+------+-----+-------------------+----------------+
| qbsql_id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| TxnID | varchar(40) | YES | MUL | NULL | |
| Customer_ListID | varchar(40) | YES | MUL | NULL | |
| Customer_FullName | varchar(255) | YES | | NULL | |
+--------------------------------+------------------+------+-----+-------------------+----------------+
Table: qb_invoice_invoiceline
+-------------------------+------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------------------+------------------+------+-----+-------------------+----------------+
| qbsql_id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| Invoice_TxnID | varchar(40) | YES | MUL | NULL | |
| Item_ListID | varchar(40) | YES | MUL | NULL | |
| Item_FullName | varchar(255) | YES | | NULL | |
+-------------------------+------------------+------+-----+-------------------+----------------+
Table: qb_customer
+-------------------------------------+------------------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------------------------------+------------------+------+-----+-------------------+----------------+
| qbsql_id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| ListID | varchar(40) | YES | MUL | NULL | |
| Name | varchar(41) | YES | MUL | NULL | |
+-------------------------------------+------------------+------+-----+-------------------+----------------+
鉴于 Item_ListID ，我想要一个快速，高效的查询来返回 Item_ListID 的列表以及订购每件商品的客户数量的COUNT在列表中，所有客户都有最初提供的 Item_ListID 。
现在我有以下SQL可行，但速度很慢：
SELECT qb_invoice_invoiceline.Item_FullName, count(*) as 'nummy'
FROM qb_invoice_invoiceline
WHERE qb_invoice_invoiceline.Invoice_TxnID =
ANY (SELECT qb_invoice.TxnID
FROM qb_invoice
INNER JOIN qb_customer ON qb_invoice.Customer_ListID = qb_customer.ListID
INNER JOIN qb_invoice_invoiceline ON qb_invoice.TxnID = qb_invoice_invoiceline.Invoice_TxnID
WHERE qb_invoice_invoiceline.Item_ListID = '1360000-57')
GROUP BY qb_invoice_invoiceline.Item_ListID
ORDER BY nummy DESC
感谢您的帮助！
这是'解释'输出：
+----+--------------------+------------------------+-------+---------------------------+-------------+---------+-----------------------------------------+-------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+--------------------+------------------------+-------+---------------------------+-------------+---------+-----------------------------------------+-------+----------------------------------------------+
| 1 | PRIMARY | qb_invoice_invoiceline | index | NULL | Item_ListID | 123 | NULL | 19690 | Using where; Using temporary; Using filesort |
| 2 | DEPENDENT SUBQUERY | qb_invoice_invoiceline | ref | Invoice_TxnID,Item_ListID | Item_ListID | 123 | const | 8 | Using where |
| 2 | DEPENDENT SUBQUERY | qb_invoice | ref | Customer_ListID,TxnID | TxnID | 123 | func | 206 | Using where |
| 2 | DEPENDENT SUBQUERY | qb_customer | ref | ListID | ListID | 123 | devdb.qb_invoice.Customer_ListID | 18 | Using where; Using index |
+----+--------------------+------------------------+-------+---------------------------+-------------+---------+-----------------------------------------+-------+----------------------------------------------+
答案 0 :(得分：0)
如果您要加入的varchar字段上没有可用的索引，则查询可能会很慢。您能详细介绍这些表中的索引吗？
我认为该查询将受益于qb_invoice.TxnID和qb_customer.ListID以及qb_invoice_invoiceline.Item_ListID上的索引。