postgresql 添加查询中不存在的列
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Adding A Column that doesn't exist in a query
提问by Devin Dixon
I want to add a column in a query that does not exist in a table and return it as a result. So lets say TABLE_TEST has column A, B and I want to return values for A, B and C. I am trying to do
我想在表中不存在的查询中添加一列并将其作为结果返回。所以让我们说 TABLE_TEST 有 A、B 列，我想返回 A、B 和 C 的值。我正在尝试做
SELECT A, B, C=3 FROM TABLE_TEST
or
或者
SELECT *, C=3 FROM TABLE_TEST
Can this be done in MySQL, Postgresel or MSSQL?
这可以在 MySQL、Postgresel 或 MSSQL 中完成吗？
回答by Pablo Santa Cruz
Yes, sure:
是的，当然：
select a, b, 3 as c from table_test
That's it. It works on three db engines you've mentioned.
而已。它适用于您提到的三个数据库引擎。
回答by Marco
You should use:
你应该使用：
SELECT A,B, 3 AS C FROM TABLE_TEST
回答by anishMarokey
you can use as
你可以用作
Select a,b, 3 as c from table
This is known as alias
这被称为 alias
