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Question

我正在使用PostgreSQL和Node.js. 我有2个表（cases和countries）：

db=# SELECT * FROM cases;

  id  |  disease   |    country     | year |   value    |   rate    
------+------------+----------------+------+------------+----------
    1 | Polio      | Albania        | 2016 | 15.00      |
    2 | Polio      | Austria        | 2016 | 10.00      |
    3 | Polio      | Belgium        | 2016 | 55.00      |
    4 | Polio      | Albania        | 2015 | 120.00     |
    5 | Polio      | Austria        | 2015 | 48.00      |
    6 | Polio      | Belgium        | 2015 | 85.00      |
    7 | Polio      | Albania        | 2014 | 0.00       |
    8 | Polio      | Austria        | 2014 | 1.00       |
    9 | Polio      | Belgium        | 2014 | 3.00       |
   10 | Tet        | Albania        | 2016 | 6.00       |
   11 | Tet        | Austria        | 2016 | 7.00       |
   12 | Tet        | Belgium        | 2016 | 10.00      |
   13 | Tet        | Albania        | 2015 | 0.00       |
   14 | Tet        | Austria        | 2015 | 78.00      |
   15 | Tet        | Belgium        | 2015 | 900.00     |
   16 | Tet        | Albania        | 2014 | 10.00      |
   17 | Tet        | Austria        | 2014 | 12.00      |
   18 | Tet        | Belgium        | 2014 | 34.00      |

db=# SELECT * FROM countries;

  id  |    country     | year | population  | capital | area
------+----------------+------+-------------+---------+------
    1 | Albania        | 2018 | 2934363.00  |         |
    2 | Albania        | 2017 | 2930187.00  |         |
    3 | Albania        | 2016 | 2926348.00  |         |
    4 | Albania        | 2015 | 2923352.00  |         |
    5 | Albania        | 2014 | 2920775.00  |         |
    6 | Austria        | 2018 | 8751820.00  |         |
    7 | Austria        | 2017 | 8735453.00  |         |
    8 | Austria        | 2016 | 8712137.00  |         |
    9 | Austria        | 2015 | 8678657.00  |         |
   10 | Austria        | 2014 | 8633220.00  |         |
   11 | Belgium        | 2018 | 11498519.00 |         |
   12 | Belgium        | 2017 | 11429336.00 |         |
   13 | Belgium        | 2016 | 11358379.00 |         |
   14 | Belgium        | 2015 | 11287940.00 |         |
   15 | Belgium        | 2014 | 11219161.00 |         |

我想通过计算rate相对于cases的费率填写cases表的population列。

所以这是我应该做的计算：

Example of Albania/Polio/2016: (value/population)*100*1000 = (15.00/2926348.00)*100*1000 = 0.51
Example of Belgium/Tet/2015:   (value/population)*100*1000 = (900.00/11287940.00)*100*1000 = 7.97

请注意，cases中的年份从2014年到2016年，而countries表中的年份从2014年到2018年。

我该怎么做？

更新

如果我使用pgAdmin 4运行使用 Igor Romanchenko 建议的查询，则可以正常运行。但是，如果我使用此方法运行查询，则会出现错误。

功能：

methods.fillRateColumnCases = async function() {
    var queryFillRate = {
        text: 'UPDATE cases' + 
                    'SET rate = (cases.value / c.population) * 100 * 1000' + 
                    'FROM countries c' +
                    'WHERE c.country = cases.country AND c.year = cases.year;'
    };
    return await client.query(queryFillRate)
    .then(function(res) {
        console.log('Table \'cases\' filled with \'rate\' values');
    })
    .catch(function(err) { 
        console.log('Error filling \'rate\' column of table \'cases\'', err.stack);
    }); 
}

错误：

Error filling 'rate' column of table 'cases' error: errore di sintassi a o presso "="
    at Connection.parseE (C:\...\node_modules\pg\lib\con
nection.js:545:11)
    at Connection.parseMessage (C:\...\node_modules\pg\l
ib\connection.js:370:19)
    at Socket.<anonymous> (C:\...\node_modules\pg\lib\co
nnection.js:113:22)
    at emitOne (events.js:116:13)
    at Socket.emit (events.js:211:7)
    at addChunk (_stream_readable.js:263:12)
    at readableAddChunk (_stream_readable.js:250:11)
    at Socket.Readable.push (_stream_readable.js:208:10)
    at TCP.onread (net.js:594:20)

Answer 1

在Postgres中，您可以将其标记为update：

update cases
    set rate = (cases.value / c.population) * 100 * 1000 
    from countries c
    where c.country = cases.country and c.year = cases.year;

计算表中度量相对于另一个表中的值的比率

更新

1 个答案: