请教sql优化（内有建表语句与题目）

[dinghun8leech]

目的：性能优化；
建表语句与初始数据：

drop database if exists test1;
create database test1;
use test1;

/** 产品分类表 */
create table productType (
       typeId varchar(20) not null primary key, /*分类id*/
       name varchar(50),  /*分类名*/
       fatherTypeId varchar(20)  /*上级分类*/
);

/** 产品表 */
create table product (
       sku varchar(20) not null primary key,  /*库存量单位，可看作商品id*/
       name varchar(50),  /*商品名*/
       maxPrice double,  /*最高价*/
       minPrice double,  /*最低价*/
       normalCount int,  /*良品库存*/
       normalSellCount int,  /*可销售的良品数*/
       badCount int  /*损坏件数*/
);

/** 产品分类关系表 */
create table register (
       typeId varchar(20),
       sku varchar(20),
       primary key (typeId, sku)
);

insert into productType values('hf1', 'erji', null);
insert into productType values('hf2', 'taishishebei', null);
insert into productType values('hf3', 'zhoubian', null);
insert into productType values('hf4', 'cd', null);

insert into productType values('hf1-1', 'ruer', 'hf1');
insert into productType values('hf1-2', 'ergua', 'hf1');
insert into productType values('hf1-3', 'bianxie', 'hf1');
insert into productType values('hf1-4', 'toudai', 'hf1');
insert into productType values('hf1-5', 'dongquan', 'hf1');
insert into productType values('hf1-6', 'dongtie', 'hf1');
insert into productType values('hf1-7', 'jingdian', 'hf1');
insert into productType values('hf2-1', 'zhuanpan', 'hf2');
insert into productType values('hf2-2', 'jiema', 'hf2');
insert into productType values('hf2-3', 'erfang', 'hf2');
insert into productType values('hf2-4', 'yitiji', 'hf2');
insert into productType values('hf3-1', 'xiancai', 'hf3');
insert into productType values('hf3-2', 'jiemian', 'hf3');
insert into productType values('hf4-1', 'jpop', 'hf4');
insert into productType values('hf4-2', 'jazz', 'hf4');
insert into productType values('hf4-3', 'bossanova', 'hf4');
insert into productType values('hf4-4', 'ost', 'hf4');

insert into product values('0001', 'hd600', 1900, 1600, 800, 700, 50);
insert into register values('hf1-4', '0001');
insert into register values('hf1-5', '0001');
insert into product values('0002', 'hd800', 12000, 7000, 10, 7, 0);
insert into register values('hf1-4', '0002');
insert into register values('hf1-5', '0002');
insert into product values('0003', 'sr009', 31000, 27000, 21, 17, 1);
insert into register values('hf1-4', '0003');
insert into register values('hf1-7', '0003');
insert into product values('0004', 'e4c', 2500, 1700, 300, 250, 13);
insert into register values('hf1-1', '0004');
insert into register values('hf1-6', '0004');
insert into product values('0005', 'ew9', 1380, 950, 5, 1, 0);
insert into register values('hf1-2', '0005');
insert into register values('hf1-5', '0005');
insert into product values('0006', 'esw11ltd', 6700, 4360, 7, 1, 0);
insert into register values('hf1-3', '0006');
insert into register values('hf1-5', '0006');
insert into product values('0007', 't1', 8900, 6800, 20, 15, 1);
insert into register values('hf1-4', '0007');
insert into register values('hf1-5', '0007');
insert into product values('0008', 'r10', 75000, 11000, 2, 2, 0);
insert into register values('hf1-4', '0008');
insert into register values('hf1-5', '0008');
insert into product values('0009', 'qualia 010', 64000, 11000, 3, 2, 1);
insert into register values('hf1-4', '0009');
insert into register values('hf1-5', '0009');
insert into product values('0010', 'esw9', 1980, 1900, 22, 20, 1);
insert into register values('hf1-3', '0010');
insert into register values('hf1-5', '0010');
insert into product values('0011', 'sr007', 17000, 16000, 10, 9, 1);
insert into register values('hf1-4', '0011');
insert into register values('hf1-7', '0011');
insert into product values('0012', 'ad900', 1900, 1550, 15, 12, 1);
insert into register values('hf1-4', '0012');
insert into register values('hf1-5', '0012');
insert into product values('0021', 'mdac2a', 1900, 1850, 37, 30, 1);
insert into register values('hf2-2', '0021');
insert into register values('hf2-3', '0021');
insert into register values('hf2-4', '0021');
insert into product values('0022', 'lyra2', 18500, 17200, 20, 8, 0);
insert into register values('hf2-2', '0022');
insert into register values('hf2-3', '0022');
insert into register values('hf2-4', '0022');
insert into product values('0023', 'hilo', 17500, 17000, 25, 4, 0);
insert into register values('hf2-2', '0023');
insert into register values('hf2-3', '0023');
insert into register values('hf2-4', '0023');
insert into product values('0024', 'ha5000', 12000, 9800, 20, 9, 0);
insert into register values('hf2-3', '0024');
insert into product values('0025', 'dac32', 18500, 12100, 50, 47, 1);
insert into register values('hf2-2', '0025');
insert into product values('0026', 'mdac3', 1900, 1600, 100, 99, 1);
insert into register values('hf2-2', '0026');
insert into register values('hf2-3', '0026');
insert into register values('hf2-4', '0026');
insert into product values('0027', 'supermo', 11200, 9800, 75, 66, 2);
insert into register values('hf2-1', '0027');
insert into product values('0028', 'd100', 2980, 2750, 80, 80, 0);
insert into register values('hf2-1', '0028');
insert into product values('0031', 'qed audio s', 2400, 2200, 150, 130, 0);
insert into register values('hf3-1', '0031');
insert into product values('0032', 'amazon basic', 25, 21, 2750, 2749, 1);
insert into register values('hf3-1', '0032');
insert into product values('0033', 'ova', 1140, 1100, 500, 8, 0);
insert into register values('hf3-2', '0033');
insert into product values('0034', 'sp2', 4850, 4700, 2, 2, 0);
insert into register values('hf3-2', '0034');
insert into product values('0041', 'aaaa', 50, 50, 12, 9, 0);
insert into register values('hf4-1', '0041');
insert into register values('hf4-4', '0041');
insert into product values('0042', 'bbbb', 300, 295, 5, 5, 0);
insert into register values('hf4-2', '0042');
insert into product values('0043', 'cccc', 200, 195, 75, 65, 0);
insert into register values('hf4-2', '0043');

题目：
1、查询各二级类目下最高价低于3000，好件可卖数>10的所有商品sku数，并按sku数排序。
2、查询当前一级类目名为erji，taishishebei下的可卖数低于10的商品明细。
3、查出划分到不止一个二级类目下的所有商品，统一只保留按字母顺序的第一个类目关系。

我的答案：
第一题：

select t.typeId, t.name, t.skuCount
from (
select typ.typeId as typeId, typ.name as name, count(prod.sku) as skuCount
from product prod left join register reg on reg.sku = prod.sku
     left join productType typ on reg.typeId = typ.typeId
where not isNull(typ.fatherTypeId) and prod.maxPrice < 3000 and prod.normalSellCount > 10
group by typ.typeId
) t
order by t.skuCount;

第二题（in or exists）：

select prod.* 
from product prod 
where prod.normalSellCount < 10
and prod.sku in (
    select distinct reg.sku
    from productType typ1 left join productType typ2 on typ1.typeId = typ2.fatherTypeId 
         left join register reg on reg.typeId = typ2.typeId
    where typ1.name = 'erji' or typ1.name = 'taishishebei'
);

select prod.* 
from product prod 
where prod.normalSellCount < 10
and exists (
    select null
    from register reg left join productType typ2 on reg.typeId = typ2.typeId
         left join productType typ1 on typ2.fatherTypeId = typ1.typeId
    where (typ1.name = 'erji' or typ1.name = 'taishishebei')
           and reg.sku = prod.sku
);

第三题（in or exists）：

select distinct prod.*, typ2.name as typeName
from product prod left join register reg on reg.sku = prod.sku
     left join productType typ1 on reg.typeId = typ1.typeId
     left join productType typ2 on typ1.fatherTypeId = typ2.typeId 
where prod.sku in (
    select reg.sku
    from product prod left join register reg on reg.sku = prod.sku 
         left join productType typ on reg.typeId = typ.typeId
    where not isNUll(typ.fatherTypeId) group by reg.sku having count(typ.typeId) > 1
) order by typ2.name;

select distinct prod.*, typ2.name as typeName
from product prod left join register reg on reg.sku = prod.sku
     left join productType typ1 on reg.typeId = typ1.typeId
     left join productType typ2 on typ1.fatherTypeId = typ2.typeId 
where exists (
    select null 
    from register reg left join productType typ2 on reg.typeId = typ2.typeId
         left join productType typ1 on typ2.fatherTypeId = typ1.typeId
    where reg.sku = prod.sku
          group by(reg.sku) having count(reg.typeId) > 1
) order by typ2.name;

请教各位前辈，此三题还有什么解法，效率更高？？谢谢。

[ACMAIN_CHM]

贴出所有相关表的 show index from .. 然后再贴出 explain select ...

[dinghun8leech]

引用 1 楼 ACMAIN_CHM 的回复:

贴出所有相关表的 show index from .. 然后再贴出 explain select ...

版主抱歉，今天略忙，我明天再按此要求，贴出相关表的索引信息，与上述三条sql的执行计划信息。

[dinghun8leech]

product表：

+---------+------------+----------+--------------+-------------+-----------+----
---------+----------+--------+------+------------+---------+
| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Car
dinality | Sub_part | Packed | Null | Index_type | Comment |
+---------+------------+----------+--------------+-------------+-----------+----
---------+----------+--------+------+------------+---------+
| product |          0 | PRIMARY  |            1 | sku         | A         |
      27 |     NULL | NULL   |      | BTREE      |         |
+---------+------------+----------+--------------+-------------+-----------+----
---------+----------+--------+------+------------+---------+

productType表：

+-------------+------------+----------+--------------+-------------+-----------+
-------------+----------+--------+------+------------+---------+
| Table       | Non_unique | Key_name | Seq_in_index | Column_name | Collation |
 Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------------+------------+----------+--------------+-------------+-----------+
-------------+----------+--------+------+------------+---------+
| productType |          0 | PRIMARY  |            1 | typeId      | A         |
          21 |     NULL | NULL   |      | BTREE      |         |
+-------------+------------+----------+--------------+-------------+-----------+
-------------+----------+--------+------+------------+---------+

register表：

+----------+------------+----------+--------------+-------------+-----------+---
----------+----------+--------+------+------------+---------+
| Table    | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Ca
rdinality | Sub_part | Packed | Null | Index_type | Comment |
+----------+------------+----------+--------------+-------------+-----------+---
----------+----------+--------+------+------------+---------+
| register |          0 | PRIMARY  |            1 | typeId      | A         |
       48 |     NULL | NULL   |      | BTREE      |         |
| register |          0 | PRIMARY  |            2 | sku         | A         |
       48 |     NULL | NULL   |      | BTREE      |         |
+----------+------------+----------+--------------+-------------+-----------+---
----------+----------+--------+------+------------+---------+

第一题执行计划：

+----+-------------+------------+-------+---------------+---------+---------+---
---------------+------+--------------------------+
| id | select_type | table      | type  | possible_keys | key     | key_len | re
f              | rows | Extra                    |
+----+-------------+------------+-------+---------------+---------+---------+---
---------------+------+--------------------------+
|  1 | PRIMARY     | <derived2> | ALL   | NULL          | NULL    | NULL    | NU
LL             |   11 | Using filesort           |
|  2 | DERIVED     | typ        | index | PRIMARY       | PRIMARY | 22      | NU
LL             |   21 | Using where              |
|  2 | DERIVED     | reg        | ref   | PRIMARY       | PRIMARY | 22      | te
st1.typ.typeId |    2 | Using where; Using index |
|  2 | DERIVED     | prod       | ref   | PRIMARY       | PRIMARY | 22      | te
st1.reg.sku    |    1 | Using where              |
+----+-------------+------------+-------+---------------+---------+---------+---
---------------+------+--------------------------+

第二题执行计划：

+----+--------------------+-------+------+---------------+---------+---------+--
-----------------------+------+--------------------------+
| id | select_type        | table | type | possible_keys | key     | key_len | r
ef                     | rows | Extra                    |
+----+--------------------+-------+------+---------------+---------+---------+--
-----------------------+------+--------------------------+
|  1 | PRIMARY            | prod  | ALL  | NULL          | NULL    | NULL    | N
ULL                    |   27 | Using where              |
|  2 | DEPENDENT SUBQUERY | typ2  | ALL  | PRIMARY       | NULL    | NULL    | N
ULL                    |   21 | Using temporary          |
|  2 | DEPENDENT SUBQUERY | typ1  | ref  | PRIMARY       | PRIMARY | 22      | t
est1.typ2.fatherTypeId |    1 | Using where              |
|  2 | DEPENDENT SUBQUERY | reg   | ref  | PRIMARY       | PRIMARY | 44      | t
est1.typ2.typeId,func  |    1 | Using where; Using index |
+----+--------------------+-------+------+---------------+---------+---------+--
-----------------------+------+--------------------------+

第三题执行计划：

+----+--------------------+-------+-------+---------------+---------+---------+-
------------------------+------+----------------------------------------------+
| id | select_type        | table | type  | possible_keys | key     | key_len |
ref                     | rows | Extra                                        |
+----+--------------------+-------+-------+---------------+---------+---------+-
------------------------+------+----------------------------------------------+
|  1 | PRIMARY            | prod  | ALL   | NULL          | NULL    | NULL    |
NULL                    |   27 | Using where; Using temporary; Using filesort |
|  1 | PRIMARY            | reg   | index | NULL          | PRIMARY | 44      |
NULL                    |   48 | Using index                                  |
|  1 | PRIMARY            | typ1  | ref   | PRIMARY       | PRIMARY | 22      |
test1.reg.typeId        |    1 |                                              |
|  1 | PRIMARY            | typ2  | ref   | PRIMARY       | PRIMARY | 22      |
test1.typ1.fatherTypeId |    1 |                                              |
|  2 | DEPENDENT SUBQUERY | typ   | ALL   | PRIMARY       | NULL    | NULL    |
NULL                    |   21 | Using where; Using temporary; Using filesort |
|  2 | DEPENDENT SUBQUERY | reg   | ref   | PRIMARY       | PRIMARY | 22      |
test1.typ.typeId        |    2 | Using where; Using index                     |
|  2 | DEPENDENT SUBQUERY | prod  | ref   | PRIMARY       | PRIMARY | 22      |
test1.reg.sku           |    1 | Using index                                  |
+----+--------------------+-------+-------+---------------+---------+---------+-
------------------------+------+----------------------------------------------+

[dinghun8leech]

顶一下~ 要6个字？