Trigger help Column value before and after update

i need to code a trigger that detects when the column of a table has changed and the records the before and after values for the column in a table.. How do I go about constructing the trigger (sql server 2008R2)
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Scott PletcherSenior DBACommented:
Is this for a single, specific column or for multiple/all columns?

The general approach is the same, but I'd strongly urge you to dynamically generate code if it's for more than one column.

Here's the general structure for a single column:

ON dbo.table_name
INSERT INTO dbo.log_table ( table_name, column_name, old_value, new_value )
SELECT 'table_name', 'column1', d.column1, i.column1
FROM inserted i
INNER JOIN deleted d ON
    d.key_value = i.key_value AND
    ISNULL(d.column1, '~~') <> ISNULL(i.column1, '~~')
bensonwalkerAuthor Commented:
No this is one column... sorry not sure what you mean by dynamically generate code?
Scott PletcherSenior DBACommented:
For one column you don't need to worry about.  Something like above will do what you need.

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Microsoft SQL Server 2008

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