SQL 服务器：select 并添加到相同 table 的新列

Question

给定那种语法

SELECT 'all the left part of 'email' column before @'
FROM [dbname].[tablename]

如何将 SELECT 查询插入到名为 'email_left' 的新列中？

PS。为简单起见，我在 select 查询后不显示长查询。

Answer 1

这是一个更新：

UPDATE x
SET    [new column created outside this statement] = 'all the left part of "email" column before @'
FROM [dbname].[tablename] AS x

Answer 2

另一个解决方案——计算列

ALTER TABLE dbo.table_name
    ADD column_name AS 'all the left part of ' + email + ' column before @'
GO

更新-

IF OBJECT_ID('dbo.email', 'U') IS NOT NULL
    DROP TABLE dbo.email
GO

SELECT email
INTO dbo.email
FROM [dbname].[tablename]
GO

--CREATE CLUSTERED INDEX index_name ON dbo.email (email)

SQL 服务器：select 并添加到相同 table 的新列

SQL Server : select and add to new column of same table

sql-server

select

insert-into