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PODetecting negative change and acting upon this
 

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    <p>I have this table where I only want to look at AB</p> <pre><code>ID CODE COUNT 102 AB 9 101 AB 8 100 AC 23 //not important!!!! 99 AB 7 98 AB 6 97 AB 5 96 AB 0 </code></pre> <p>And I then want to count the differences between the specific ID's which have CODE 'AB'</p> <p>So</p> <pre><code>Step 1: 9 - 8 = 1 // (corrected sample data. this line was wrong) Step 2: 8 - 7 = 1 Step 3: 7 - 6 = 1 Step 4: 6 - 5 = 1 Step 5: 5 - 0 = 5 </code></pre> <p>This I do by this query made by @bonCodigo</p> <pre><code>select ID, DIFFERENCE, COUNT from ( SELECT t.ID, t.CODE, t.COUNT, @PREVCOUNT, @PREVCOUNT - t.COUNT DIFFERENCE, @PREVCOUNT := t.COUNT -- Updates for the next iteration, so it -- must come last! FROM (SELECT ID, CODE, COUNT FROM some_table WHERE CODE = 'AB' ORDER BY ID DESC) t, (SELECT @PREVCOUNT := NULL) _uv group by t.id, t.code )x where x.difference &gt;= 0 order by ID DESC; </code></pre> <p>As my new incoming data sometimes RESETS the count, it starts counting from 0 till whatever.</p> <p>So sometimes I get data in this order:</p> <pre><code>ID COUNT 1. 0 2. 1 3. 2 4. 7 5. 4 // which means the counter has reset to 0 and counted up to 4 again. 6. 5 </code></pre> <p>Now what my query is doing, it counts only the positive changes and takes this as a difference. </p> <p>So what it does:</p> <pre><code>Step 1: 1 - 0 = 1 Step 2: 2 - 1 = 1 Step 3: 7 - 2 = 5 Step 4: 4 - 7 = -3 //discarded as this difference is smaller than 0 Step 5: 5 - 4 = 1 </code></pre> <p>So if I SUM() this I get <strong>8</strong> <a href="http://sqlfiddle.com/#!2/6924a/2" rel="nofollow">http://sqlfiddle.com/#!2/6924a/2</a></p> <p>While I want this code to count from 0 as soon as there is a negative difference</p> <p>So what I want:</p> <pre><code>Step 1: 1 - 0 = 1 Step 2: 2 - 1 = 1 Step 3: 7 - 2 = 5 Step 4: 4 - 7 = -3 BUT MAKE IT 4 because the counter started from 0 again. Step 5: 5 - 4 = 1 </code></pre> <p>So if I SUM() this I get <strong>12</strong></p>
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    1. USLazykiddy
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    1. COComplicated & unclear. I suggest breaking it into easier bites, sections, or multiple questions.
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    2. COI'm sorry, I'll try to be more clear next time.
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