SQL查询在两个表中查找不同的值？

Question

Table 1              Table 2
Number | Code        Code | Description
1234     A           A      Something
1235     B           C      Something else
1246     C           D      Something other
1247     A
1248     B
1249     A

我想找到不同的Code值并得到这样的回报:

1  |  2
-------
A     A
B
C     C
      D

我无法弄清楚如何编写一个可以返回上述结果的SQL查询.任何人都有这样或类似的查询经验？

Answer 1

在适当的RDBMS中:

SELECT
   T1.Code, T2.Code
FROM
   (SELECT DISTINCT Code FROM Table1) T1
   FULL OUTER JOIN
   (SELECT DISTINCT Code FROM Table2) T2
              ON T1.Code = T2.Code

在MySQL ... UNION删除重复项

SELECT
   T1.Code, T2.Code
FROM
   Table1 T1
   LEFT OUTER JOIN
   Table2 T2 ON T1.Code = T2.Code
UNION
SELECT
   T1.Code, T2.Code
FROM
   Table1 T1
   RIGHT OUTER JOIN
   Table2 T2 ON T1.Code = T2.Code