java - 优化帮助 : SQL Query to display minimum prices per country

Question

我为我的一个客户开发了一种类似代码的招标管理系统。这是一段代码:

try {
    Connection con = Mycon.getConnection();
    PreparedStatement ps = con.prepareStatement("TRUNCATE tempcalcplan");
    ps.executeUpdate();
    ps.clearBatch();
    ps = con.prepareStatement("INSERT INTO tempcalcplan SELECT v.conid,c.conname, v.rate, v.venid FROM venprices v LEFT JOIN  country c ON c.conid = v.conid WHERE (v.conid, v.rate) IN ( SELECT v.conid, MIN(v.rate) FROM venprices v GROUP BY v.conid) GROUP BY v.conid");
    ps.executeUpdate();
    ps.clearBatch();
    ps = con.prepareStatement("select * from tempcalcplan");

    ResultSet rs = ps.executeQuery();
    jTable1.setModel(DbUtils.resultSetToTableModel(rs));
} catch(Exception e){
    e.printStackTrace();
}

这段代码被设计为:

1. 清空表 tempcalcplan(假设存储了以前的结果。)
2. 借助 2 个不同的表(表如下所示)生成所需的数据并将其存储在 tempcalcplan 表中
3. 在 jTable 上显示 tempcalcplan 表的结果。

这是country 和tempcalcplan 表。

1. 国家(包含 30,000 条记录)

   +---------+-------------+------+-----+---------+-------+
   | Field   | Type        | Null | Key | Default | Extra |
   +---------+-------------+------+-----+---------+-------+
   | conid   | int(10)     | NO   | PRI | NULL    |       |
   | conname | varchar(50) | YES  |     | NULL    |       |
   +---------+-------------+------+-----+---------+-------+
   

2. tempcalcplan(包含 1,80,000 多条记录)

   +---------+-------------+------+-----+---------+-------+
   | Field   | Type        | Null | Key | Default | Extra |
   +---------+-------------+------+-----+---------+-------+
   | conid   | int(10)     | NO   | PRI | NULL    |       |
   | conname | varchar(50) | YES  |     | NULL    |       |
   | rate    | double      | YES  |     | NULL    |       |
   | venid   | varchar(50) | YES  |     | NULL    |       |
   +---------+-------------+------+-----+---------+-------+
   

3. venprices

   +-------+--------------+------+-----+---------+-------+
   | Field | Type         | Null | Key | Default | Extra |
   +-------+--------------+------+-----+---------+-------+
   | conid | int(10)      | NO   | PRI | NULL    |       |
   | rate  | double       | YES  |     | NULL    |       |
   | venid | varchar(50)  | NO   | PRI |         |       |
   +-------+--------------+------+-----+---------+-------+
   

结果最多需要 12-15 分钟才能显示在 jTable 中。 我想将它减少到 1-2 分钟。

Answer 1

这是可能花费最多时间的查询:

INSERT INTO tempcalcplan
    SELECT v.conid, c.conname, v.rate, v.venid
    FROM venprices v LEFT JOIN
         country c
         ON c.conid = v.conid
    WHERE (v.conid, v.rate) IN ( SELECT v.conid, MIN(v.rate) FROM venprices v GROUP BY v.conid) GROUP BY v.conid");

我的猜测是 WHERE 子句导致了问题。尝试将其移至 FROM 子句:

    SELECT v.conid, c.conname, v.rate, v.venid
    FROM venprices v LEFT JOIN
         country c
         ON c.conid = v.conid JOIN
         (SELECT v.conid, MIN(v.rate) as rate
          FROM venprices v
          GROUP BY v.conid
         ) vr
         ON v.conid = vr.conid and v.rate = vr.rate;

我认为您的索引已针对此查询设置得很好。