Why does my BigQuery UPDATE fail when replacing 0 values with NULL using CASE statements?

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Kapil

Updated 7 hours ago in

I’m cleaning a weather dataset in Google BigQuery where missing values in wind_speed and visibility were incorrectly stored as 0.

I tried updating the table like this:

UPDATE `my_project.weather_data.tracks_2023`

SET

wind_speed = CASE WHEN wind_speed = 0 THEN NULL END,

visibility = CASE WHEN visibility = 0 THEN NULL END

WHERE wind_speed = 0 OR visibility = 0;

The query returns an error.

My goal is simple:

Convert 0 values in wind_speed to NULL
Convert 0 values in visibility to NULL
Leave all other values unchanged

What’s the correct way to do this in BigQuery?

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<div class="markdown prose dark:prose-invert wrap-break-word w-full light markdown-new-styling">
<p class="PDq2pG_selectionAnchorContainer" data-start="109" data-end="244">I’m cleaning a weather dataset in Google BigQuery where missing values in <code data-start="183" data-end="195">wind_speed</code> and <code data-start="200" data-end="212">visibility</code> were incorrectly stored as <code data-start="240" data-end="243">0</code>.</p>
<p data-start="246" data-end="283">I tried updating the table like this:</p>
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<div class="cm-line"><span class="ͼg">UPDATE</span> `my_project.weather_data.tracks_2023`</div>
<div class="cm-line"><span class="ͼg">SET</span></div>
<div class="cm-line">wind_speed <span class="ͼg">=</span> <span class="ͼg">CASE</span> <span class="ͼg">WHEN</span> wind_speed <span class="ͼg">=</span> <span class="ͼj">0</span> <span class="ͼg">THEN</span> <span class="ͼj">NULL</span> <span class="ͼg">END</span>,</div>
<div class="cm-line">visibility <span class="ͼg">=</span> <span class="ͼg">CASE</span> <span class="ͼg">WHEN</span> visibility <span class="ͼg">=</span> <span class="ͼj">0</span> <span class="ͼg">THEN</span> <span class="ͼj">NULL</span> <span class="ͼg">END</span></div>
<div class="cm-line"><span class="ͼg">WHERE</span> wind_speed <span class="ͼg">=</span> <span class="ͼj">0</span> <span class="ͼg">OR</span> visibility <span class="ͼg">=</span> <span class="ͼj">0</span>;</div>
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<p data-start="495" data-end="522">The query returns an error.</p>
<p data-start="524" data-end="542">My goal is simple:</p>
<ul data-start="543" data-end="671">
<li data-section-id="1y0x0sc" data-start="543" data-end="589">Convert <code data-start="553" data-end="556">0</code> values in <code data-start="567" data-end="579">wind_speed</code> to <code data-start="583" data-end="589">NULL</code></li>
<li data-section-id="w9gniu" data-start="590" data-end="636">Convert <code data-start="600" data-end="603">0</code> values in <code data-start="614" data-end="626">visibility</code> to <code data-start="630" data-end="636">NULL</code></li>
<li data-section-id="pf4yvr" data-start="637" data-end="671">Leave all other values unchanged</li>
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<p data-start="673" data-end="719">What’s the correct way to do this in BigQuery?</p>
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