结合2个不同但非常相似的表格

Question

我有2个相似但不相同的表,因此不可能使用联合.我需要结合表格,记住大约有40列,其中只有20列是共同的.关于最佳方法的任何想法？

Table1

ActivityCategory    ActivityType   Nationality   Language
---------------------------------------------------------
Communication       Telephone      French        French
Meeting             Session        British       English


Table2

ActivityCategory    ActivityType   Nationality   Employment
-----------------------------------------------------------
Communication       Fax            American      Employed


Combined Table

ActivityCategory    ActivityType   Nationality   Language   Employment
----------------------------------------------------------------------
Communication       Telephone      French        French
Meeting             Session        British       English
Communication       Fax            American                 Employed

Answer 1

做一个UNION,但首先你必须使表格结构相同.

在SELECT for Table1中,将Employment添加为NULL值列

在SELECT for Table2中,将Language添加为NULL值列

SELECT ActivityCategory, ActivityType, Nationality, Language, NULL AS Employment
FROM Table1
UNION
SELECT ActivityCategory, ActivityType, Nationality, NULL AS Language, Employment
FROM Table1