The following Microsoft SQL Server T-SQL code sample demonstrate how to read a Windows environment variable.

-- Display all environment variables

EXEC master..xp_cmdshell 'set'

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-- Retrieve a single environment variable - Read environment variable

DECLARE @EnvVar nvarchar(256)

CREATE TABLE #Upload(EnvVar nvarchar(256))

INSERT INTO #Upload

EXEC xp_cmdshell 'echo %USERDOMAIN%'

DELETE #Upload WHERE EnvVar is NULL OR EnvVar = ''

SET @EnvVar = (SELECT EnvVar from #Upload)

SELECT @EnvVar as [User Domain]

/* User Domain

ENTERPRISE */

DROP TABLE #Upload

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Related link: Setting Environment variables