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我对 2 个表 lineitem 和 part 的连接有一个查询，

select
        sum(l_extendedprice* (1 - l_discount)) as revenue
from
        lineitem force index for join (l_pk),
        part
where
        (
                p_partkey = l_partkey
                and p_brand = 'Brand#12'
                and p_container in ('SM CASE', 'SM BOX', 'SM PACK', 'SM PKG')
                and l_quantity >= 1 and l_quantity <= 1 + 10
                and p_size between 1 and 5 
                and l_shipmode in ('AIR', 'AIR REG')
                and l_shipinstruct = 'DELIVER IN PERSON'
        )
        or
        (
                p_partkey = l_partkey
                and p_brand = 'Brand#23'
                and p_container in ('MED BAG', 'MED BOX', 'MED PKG', 'MED PACK')
                and l_quantity >= 10 and l_quantity <= 10 + 10
                and p_size between 1 and 10
                and l_shipmode in ('AIR', 'AIR REG')
                and l_shipinstruct = 'DELIVER IN PERSON'
        )
        or
        (
                p_partkey = l_partkey
                and p_brand = 'Brand#34'
                and p_container in ('LG CASE', 'LG BOX', 'LG PACK', 'LG PKG')
                and l_quantity >= 20 and l_quantity <= 20 + 10
                and p_size between 1 and 15
                and l_shipmode in ('AIR', 'AIR REG')
                and l_shipinstruct = 'DELIVER IN PERSON'
        );

在 lineitem 上有索引，尝试使用索引进行连接 p_partkey = l_partkey

create index l_pk on tpch.lineitem(l_partkey);

我尝试让mysql解释它并显示

| id | select_type | table    | type   | possible_keys | key     | key_len | ref                     | rows    | Extra       |       
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+---------+-------------+
|  1 | SIMPLE      | lineitem | ALL    | l_pk          | NULL    | NULL    | NULL                    | 5982534 | Using where | 
|  1 | SIMPLE      | part     | eq_ref | PRIMARY       | PRIMARY | 4       | tpch.lineitem.L_PARTKEY |       1 | Using where | 
+----+-------------+----------+--------+---------------+---------+---------+-------------------------+---------+-------------+

我不明白为什么不使用索引 l_pk ？

谢谢！

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