Question

我有以下查询：

SELECT t1.Material, t1.Amount, t2.amtLast, t3.amtLast
FROM FAUF t1
LEFT JOIN
     (SELECT FAUF.Material AS mat, FAUF.Amount AS amtLast
     FROM FAUF
     WHERE (year=2014)) t2
     ON (t1.Material = t2.mat)
LEFT JOIN
     (SELECT FAUF.Material AS mat, FAUF.Amount AS amtLast
     FROM FAUF
     WHERE (year=2013)) t3
     ON (t1.Material = t3.mat)
WHERE (t1.year=2015);

MS Access给我一个错误，即（t1.Material = t2.mat）中缺少表达式。如果我排除了最后一次JOIN查询的工作原理，我缺少什么？

Answer 1

MS Access需要额外的括号才能进行连接。试试这个：

SELECT t1.Material, t1.Amount, t2.amtLast, t3.amtLast
FROM (FAUF t1 LEFT JOIN
      (SELECT FAUF.Material AS mat, FAUF.Amount AS amtLast
       FROM FAUF
       WHERE (year=2014)
      ) t2
     )
     ON (t1.Material = t2.mat) LEFT JOIN
     (SELECT FAUF.Material AS mat, FAUF.Amount AS amtLast
      FROM FAUF
      WHERE (year=2013)
    ) t3
    ON (t1.Material = t3.mat)
WHERE (t1.year = 2015);

但是，您可以使用条件聚合执行此操作，这比join方法更简单：

select f.Material,
       sum(iif(f.year = 2015, amount, 0)) as amt_2015,
       sum(iif(f.year = 2014, amount, 0)) as amt_2014,
       sum(iif(f.year = 2013, amount, 0)) as amt_2013
from fauf f
group by f.Material;

Access / SQL Query JOIN创建的表

1 个答案: