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Accepted
Hab G.
Asked: 2019-10-24 06:25:09 +0800 CST

SQL 数据库查询：如何添加新字段并分配值

  • 772

我有 3 个表，如下面的屏幕截图所示。我使用 UNION 创建了一个查询，如下所示。

在此处输入图像描述

SELECT T1_ID AS ID, T1_NAME AS NAME, T1_ADD AS ADDRESS
FROM Table1
UNION
SELECT T2_ID AS ID, T2_NAME AS NAME, T2_ADD AS ADDRESS
FROM Table2
UNION
SELECT T3_ID AS ID, T3_NAME AS NAME, T3_ADD AS ADDRESS
FROM Table3

我得到了下面的结果。

在此处输入图像描述

我的问题是，如何添加一个名为 TYPE 的列（字段）并为查询结果赋值，但不更新现有的三个表以使其像下面的屏幕截图一样？

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query

1 个回答

  1. Best Answer

    不是最优雅的解决方案，但要回答您的问题，您可以这样做：

    SELECT T1_ID AS ID, T1_NAME AS NAME, T1_ADD AS ADDRESS, 'ANIMAL' AS TYPE
FROM Table1
UNION
SELECT T2_ID AS ID, T2_NAME AS NAME, T2_ADD AS ADDRESS, 'HUMAN' AS TYPE
FROM Table2
UNION
SELECT T3_ID AS ID, T3_NAME AS NAME, T3_ADD AS ADDRESS, 'OBJECT' AS TYPE
FROM Table3
    • 0

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