mysql - 使用 MySQL 将包含相同索引的其他表中的值相乘

Question

sourceindex | source | target | prob
    1       | apple  |   dog  | 2/(2+2+1)
    2       | dog    |   cat  | 2/(2+2+1)
    3       | door   |   cat  | 1/(2+2+1)
    2       | dog    |   apple| 2/(2+2+1)  
    4       | cat    |   dog  | 2/(2+2+1)  -----step 1  table1

sourceindex | source | target | prob
    1       | apple  |   dog  | 2/(2+2+1)
    2       | dog    |   cat  | 4/(2+2+1)
    3       | door   |   cat  | 1/(2+2+1)  
    4       | cat    |   dog  | 2/(2+2+1)  -----step 2  sum the prob group by sourceindex
                                                        and output to new table 



---------------------------------------------

 sourceindex    | source | target | prob      | result  
        1       | apple  |   dog  | 2/(2+2+1) | (2/(2+2+1))*(2/(2+2+1))
        2       | dog    |   cat  | 2/(2+2+1) | (2/(2+2+1))*(4/(2+2+1))
        3       | door   |   cat  | 1/(2+2+1) | (1/(2+2+1))*(1/(2+2+1))
        2       | dog    |   apple| 2/(2+2+1) | (2/(2+2+1))*(4/(2+2+1))
        4       | cat    |   dog  | 2/(2+2+1) | (2/(2+2+1))*(2/(2+2+1))

步骤3返回与table2 prob列相乘的结果值，依赖于相同的源索引并插入到table1

Answer 1

这是预期的结果吗？

| SOURCEINDEX | SOURCE | TARGET | T1_PROB | STEP3 |
|-------------|--------|--------|---------|-------|
|           1 |  apple |    dog |   0.400 | 0.160 |
|           2 |    dog |    cat |   0.400 | 0.160 |
|           3 |   door |    cat |   0.200 | 0.040 |
|           2 |    dog |  apple |   0.400 | 0.160 |
|           4 |    cat |    dog |   0.400 | 0.160 |

这是基于此查询:

select
        t1.sourceindex
      , t1.source
      , t1.target
      , format(t1.prob,3)          as t1_prob
      , format(t1.prob*t1.prob,3)  as step3
from table1 t1
inner join table2 t2 on t1.sourceindex = t2.sourceindex
;

这个假设的数据，而不是我已经将概率从字符串减少到指示计算的数字结果。

CREATE TABLE Table1
    (`sourceindex` int, `source` varchar(5), `target` varchar(5), `prob` decimal(12,3))
;

INSERT INTO Table1
    (`sourceindex`, `source`, `target`, `prob`)
VALUES
    (1, 'apple', 'dog', 0.400),
    (2, 'dog', 'cat', 0.400),
    (3, 'door', 'cat', 0.200),
    (2, 'dog', 'apple', 0.400),
    (4, 'cat', 'dog', 0.400)
;

CREATE TABLE Table2
    (`sourceindex` int, `source` varchar(5), `target` varchar(3), `prob` decimal(12,3))
;

INSERT INTO Table2
    (`sourceindex`, `source`, `target`, `prob`)
VALUES
    (1, 'apple', 'dog', 0.400),
    (2, 'dog', 'cat', 0.800),
    (3, 'door', 'cat', 0.200),
    (4, 'cat', 'dog', 0.400)
;

参见:http://sqlfiddle.com/#!9/80d14/1您可以在其中尝试或修改它。