Question

以下查询返回0行，即使这两个表包含多个匹配值。

SELECT i.isrc, m.isrc FROM table1 i INNER JOIN table2 m ON i.isrc = m.isrc;

因为isrc列是varchar类型，所以我怀疑它可能是表排序规则的问题。但是，将两个排序规则更改为utf-8并没有解决问题。

这可能是什么问题？

Answer 1

尝试下面的内容，

SELECT i.isrc, m.isrc 
FROM table1 i 
INNER JOIN table2 m
ON UPPER(TRIM(i.isrc)) = UPPER(TRIM(m.isrc))

注意：

修剪双方的值

规范化案例

Answer 2

看一下你想法在每个表中匹配的值：

select src, sum(in1) as in1, sum(in2) as in2
from ((select distinct i.isrc as src, 1 as in1, 0 as in2 from table1 i) union all
      (select distinct m.isrc as src, 0 as in1, 1 as in2 from table1 m)
     ) t
group by src;

在执行上述操作之前，您可能会发现有用的摘要：

select in1, in2, count(*), min(src), max(src)
from (select src, sum(in1) as in1, sum(in2) as in2
      from ((select distinct i.isrc as src, 1 as in1, 0 as in2 from table1 i) union all
            (select distinct m.isrc as src, 0 as in1, 1 as in2 from table1 m)
           ) t
      group by src
     ) s
group by in1, in2;

对于group by而言相同且对于比较来说相同的语义可能不一样（最后的空格会影响group by的相似性但不应影响相似性的相等性，例如）。但是，这将让您知道两个表中可以匹配的内容。

INNER JOIN在VARCHAR上

2 个答案: