SQL SQL简单减法查询
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SQL Simple Subtraction Query
提问by Brecht De Baere
I have a Database. It contains 2 Tables. Let me call them Table A and Table B.
我有一个数据库。它包含2个表。让我称它们为表 A 和表 B。
Table A Content:
表A内容：
- Date
- Name of Supplier
- Name of Good Delivered
- Amount of Good Delivered, simply put Ingredi?nt A (Numeric Value)
- 日期
- 供应商名称
- 货物名称
- 已交付货物的数量，只需输入成分 A（数值）
Table B Content:
表B内容：
- Production Date
- Name of Product
- Ingredi?nt A
- 生产日期
- 产品名称
- 成分 A
What I exactly want is:
我真正想要的是：
Query with Table A, Column 4 minus (Subtraction) Table B, Column 3.
查询表 A，第 4 列减去（减法）表 B，第 3 列。
Extra Notes:
额外说明：
I have been asking this question to a friendly programmer. He adviced me to go through the onlince course of w3schools.com which I did. He also assumed the subtraction should belong under a certain 'Join' function.
我一直在向一位友好的程序员提出这个问题。他建议我完成 w3schools.com 的在线课程，我也是这样做的。他还假设减法应该属于某个“加入”函数。
I have also been googling and searching Stackoverflow. With no results. Even tho, I need to mention that I maybe lack finding the results because my English is quite poor.
我也一直在谷歌搜索和搜索 Stackoverflow。没有结果。即便如此，我还是要提一下，我可能找不到结果，因为我的英语很差。
I want to sincerely apologise, if my English is poor and if my question was / is poorly phrased. English is not my native language.
我想真诚地道歉，如果我的英语很差，如果我的问题是 / 措辞不当。英语不是我的母语。
If direct help is not possible, I am willing and eager to learn. If you have any sources where I can learn about simple mathematics in Querys related to Databases (Such as MS Access or OOo Base) than feel free to refer me to good and informational websites and / or courses.
如果无法直接提供帮助，我愿意并渴望学习。如果您有任何资源可以让我在与数据库相关的查询（例如 MS Access 或 OOo Base）中学习简单的数学知识，请随时向我推荐优秀的信息网站和/或课程。
Sincerely yours and with kind regards Dofty
真诚地向您致以亲切的问候 Dofty
System Information:
系统信息：
- Windows 7 - 64 Bit - Home Edition and all it's updates
- OpenOffice.org 3.3.0 - OOO330m20(Build: 9567)
- Windows 7 - 64 位 - 家庭版及其所有更新
- OpenOffice.org 3.3.0 - OOO330m20（内部版本：9567）
Reason for not upgrading OOo to latest version: Compatibility Issues with previous scripted software. And too 'less' time at the job to fix those issues for Version 4.0 and later.
未将 OOo 升级到最新版本的原因：与以前的脚本软件的兼容性问题。并且在工作中修复 4.0 及更高版本的这些问题的时间太“少”。
回答by Sinan Samet
You can just use math in SQL
你可以在 SQL 中使用数学
SELECT
(a.column_4 - b.column_3) as subtracted_value
FROM
TABLE_A as a
JOIN
TABLE_B as b ON a.id = b.table_a_id
"subtracted_value" should be the value of column 4 of table a minus column 3 of table b here. You need to join the tables using an id so you can see which row of TABLE A belongs to which row of TABLE B.
“subtracted_value”应该是表 a 第 4 列的值减去表 b 的第 3 列。您需要使用 id 连接表，以便您可以查看 TABLE A 的哪一行属于 TABLE B 的哪一行。
In this example I called the id in TABLE A "id" and the pointer in TABLE B to the id of TABLE A "table_a_id". So "id" in TABLE A and "table_a_id" in TABLE B need to be equal when they belong to the same row.
在这个例子中，我将 TABLE A 中的 id 称为“id”，将 TABLE B 中的指针称为指向 TABLE A 的 id 的指针“table_a_id”。因此，表 A 中的“id”和表 B 中的“table_a_id”在属于同一行时需要相等。
Worth taking a look at: http://www.w3schools.com/sql/sql_join.asp
回答by RobP
are you trying to do this with a SQL query? How about something based on: SELECT (SELECT COLUMN4 FROM tableA) - (SELECT COLUMN3 FROM tableB)
你想用 SQL 查询来做到这一点吗？怎么样基于： SELECT (SELECT COLUMN4 FROM tableA) - (SELECT COLUMN3 FROM tableB)
