How can I do a BEFORE UPDATED trigger with sql server?

MSSQL does not support BEFORE triggers. The closest you have is INSTEAD OF triggers but their behavior is different to that of BEFORE triggers in MySQL.

You can learn more about them here, and note that INSTEAD OF triggers "Specifies that the trigger is executed instead of the triggering SQL statement, thus overriding the actions of the triggering statements." Thus, actions on the update may not take place if the trigger is not properly written/handled. Cascading actions are also affected.

You may instead want to use a different approach to what you are trying to achieve.

It is true that there aren't "before triggers" in MSSQL. However, you could still track the changes that were made on the table, by using the "inserted" and "deleted" tables together. When an update causes the trigger to fire, the "inserted" table stores the new values and the "deleted" table stores the old values. Once having this info, you could relatively easy simulate the "before trigger" behaviour.

Can't be sure if this applied to SQL Server Express, but you can still access the "before" data even if your trigger is happening AFTER the update. You need to read the data from either the deleted or inserted table that is created on the fly when the table is changed. This is essentially what @Stamen says, but I still needed to explore further to understand that (helpful!) answer.

The deleted table stores copies of the affected rows during DELETE and UPDATE statements. During the execution of a DELETE or UPDATE statement, rows are deleted from the trigger table and transferred to the deleted table...

The inserted table stores copies of the affected rows during INSERT and UPDATE statements. During an insert or update transaction, new rows are added to both the inserted table and the trigger table...

https://msdn.microsoft.com/en-us/library/ms191300.aspx

So you can create your trigger to read data from one of those tables, e.g.

CREATE TRIGGER <TriggerName> ON <TableName>AFTER UPDATEAS  BEGIN    INSERT INTO <HistoryTable> ( <columns...>, DateChanged )    SELECT <columns...>, getdate()    FROM deleted;  END;

My example is based on the one here:

http://www.seemoredata.com/en/showthread.php?134-Example-of-BEFORE-UPDATE-trigger-in-Sql-Server-good-for-Type-2-dimension-table-updates

sql-server triggers