• Quick preface: this answer was based on the originally incorrect tag that this question was relating to SQL Server. I'm no longer aware of its validity on Oracle SQL Developer.*

ALTER TABLE Employees ADD FullName AS (FirstName + ' ' + LastName)

Although in practice I'd advise that you do that operation in your SELECT . That's somewhat personal preference, but I tend to think doing things in your end queries is a bit cleaner, more readable, and easier to maintain than storing extra, calculated columns.

Edit:

This was eventually found as the answer, and listed by the OP as a comment on this post. The following is appropriate syntax for Oracle Sql Database.

ALTER TABLE emps MODIFY (FULL_NAME VARCHAR2(50) GENERATED ALWAYS AS (first_name || ' ' || last_name) VIRTUAL);

如果在从数据库中选择时始终需要fullname列，则可以在创建employee表时创建计算列。
例如：

CREATE TABLE Employee
(
  FirstName VARCHAR(20),
  LastName VARCHAR(20),
  FullName AS CONCAT(FirstName,' ',LastName)
)

INSERT INTO Employee VALUES ('Rocky','Jeo')

SELECT * FROM Employee 

  Output:

  FirstName  LastName  FullName
  Rocky      Jeo       Rocky Jeo

这取决于您的目的，您是真的需要向数据库中添加新列，还是只需要根据需要查询出“全名”。
要动态查看，只需运行查询即可
SELECT firstname + ' ' + lastname AS FullName FROM employees
除此之外，您还可以创建一个简单的存储过程来存储它。

(For单一结果在where条件中使用等于）

select * 
from TABLE_name 
where (Column1+Column2) in (11361+280,11365+250)

In addition to @Jacky 's answer, if you are trying to add this to a query and not the table, there is also the CONCAT() function that you can use in the select statement

SELECT CONCAT(FirstName, ' ', LastName) as FullName
FROM table_name