T sql query help to calculate trend.

Hello Forum Members,

I need to calculate the trend.

Trend=Supply +Next Supply-Next Demand.

TABLE[dbo].[#Test_Trend](

[RecordNUmber][int]IDENTITY(1,1)NOTNULL,

[City][nvarchar](255)NULL,

[Date][datetime]NULL,

[Supply][float]NULL,

[Demand][float]NULL,

[Trend][float]NULL,

ON[PRIMARY]

insertinto#test_trendvalues('Seattle','05-01-2014',149,0,'')

insertinto#test_trendvalues('Seattle','06-01-2014',0,79,'')

insertinto#test_trendvalues('Seattle','07-01-2014',0,402,'')

insertinto#test_trendvalues('Seattle','08-01-2014',0,668,'')

insertinto#test_trendvalues('Austin','05-01-2014',427,0,'')

insertinto#test_trendvalues('Austin','06-01-2014',0,81,'')

insertinto#test_trendvalues('Austin','07-01-2014',0,56,'')

insertinto#test_trendvalues('Austin','08-01-2014',0,67,'')