Back To Basics: The UPDATE Statement

After you’ve inserted the data into the table, it’s time to update the data.  We do this by using the UPDATE statement.  The update statment can be used in two ways.  The first is to update a record or set of records in a single table, by simply filtering the data in the table by using values in the table.

UPDATE TableName
SET Column1 = 'Value'
WHERE AnotherColumn = 'AnotherValue'

A more complex update uses another table as the source of the data. This makes the UPDATE statement look like a combination of the UPDATE statement and the SELECT statement.

UPDATE TableName
SET Column2 = AnotherTable.Column3
FROM AnotherTable
WHERE TableName.Column1 = AnotherTable.Column1

We can add joins into this as well, so that we can update more than one column from different tables at the same time.

UPDATE TableName
SET Column2 = AnotherTable.Column3,
Column3 = ThirdTable.Column2
FROM AnotherTable
JOIN ThirdTable ON AnotherTable.Column5 = ThirdTable.Column4
WHERE TableName.Column1 = ThirdTable.Column1

I hope that you find this post useful. I encourage everyone to open up Books OnLine and read through the information on the UPDATE statement. It includes more examples, and some of the other options which are available to you.

Denny

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2 Responses

  1. I had an amazing experience a few months ago at work (I’m the SQL Server DBA). I blew the minds of my boss, who has taught SQL Server, and our GIS admin, when I told and showed them that you can update data from views. They both thought that views were read-only.

    A bit of a rude awakening for them, they did not know that permissions were equally important for views as for tables.

  2. I’m new to this forum. Aren’t two of the above SQL statements in error? Specifically:

    UPDATE TableName
    SET Column2 = AnotherTable.Column3
    FROM AnotherTable
    WHERE TableName.Column1 = TableName.Column1

    Shouldn’t the WHERE read:

    WHERE TableName.Column1 = AnotherTable.Column1

    ? Just curious…

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