Add a Column that Represents a Concatenation of Two Other Varchar Columns

问题

I have an employees table and I want to add a third column valued as the concatenation of the first and last name called "FullName". How can I accomplish that without losing any data from either of the first two columns?

回答1:

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);

回答2:

If you need fullname column all time when you select from database then you can create computed column at the time of creation of your table employee.

for example:

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

回答3:

It depends on your purpose, whether you really need to add a new column to your database, or you just need to query out the "full name" on an as-needed basis.

To view it on the fly, just run the query

SELECT firstname + ' ' + lastname AS FullName FROM employees

Beyond that, you also can create a simple Stored Procedure to store it.

回答4:

(For single result use equal to in the where condition)

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

来源：https://stackoverflow.com/questions/24729372/add-a-column-that-represents-a-concatenation-of-two-other-varchar-columns

标签

sql

Oracle

concatenation

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