MySQL update with select from another table
<p>I've got 3 tables.
Companies, Kommuner and Fylker.</p>

<p>The companies table have an empty field <code>forretningsadresse_fylke</code> but an other field <code>forretningsadresse_kommune</code> with a value. </p>

<p>So basically, I need to fill in <code>forretningsadresse_fylke</code>, based on the value of <code>forretningsadresse_kommune</code>.</p>

<p>Now, the value of <code>forretningsadresse_kommune</code> and the value I want for <code>forretningsadresse_fylke</code> is stored in the Kommuner and Fylker tables.</p>

<p>So I wrote this query, but that doesn't seem to work because after 600 seconds the "MySQL server goes away".</p>

<pre><code>UPDATE companies, fylker, kommuner
SET companies.forretningsadresse_fylke = (
    SELECT fylkeNavn 
    FROM fylker 
    WHERE fylker.fylkeID = kommuner.fylkeID
)
WHERE companies.forretningsadresse_kommune = kommuner.kommuneNavn
</code></pre>

<p>Here is what the Kommuner and Fylker tables look like.</p>

<p>Kommuner Table</p>

<p><a href="https://i.stack.imgur.com/r5ckf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/r5ckf.png" alt="enter image description here"></a></p>

<p>Fylker Table</p>

<p><a href="https://i.stack.imgur.com/9f8IV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9f8IV.png" alt="enter image description here"></a></p>

<p>Companies table
<a href="https://i.stack.imgur.com/3CDLI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3CDLI.png" alt="enter image description here"></a></p>

<p>companies Table</p>

<pre><code>            | forretningsadresse_fylke  | forretningsadresse_kommune |
            |===========================|============================|
            |                           |                            |
            |                           |                            |
            |                           |                            |
            |                           |                            |
            |                           |                            |
            |                           |                            |
</code></pre>

<p>So I was wondering if there was something wrong with the query?
Also, it might be good to mention, the table I try to update (Companies) has over 1 million rows.</p>

<p>Thanks in advance!</p>