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PO3 joins and where clause together
 

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    <p>I have 3 tables</p> <pre><code>bl_main (bl_id UNIQUE, bl_area) bl_details (bl_id UNIQUE, name) bl_data(bl_id, month, paper_tons, bottles_tons) </code></pre> <p><code>bl_id</code> is not unique in the last table. There will be multiple rows of same <code>bl_id</code>. </p> <p>I am trying to retrieve data in the following way</p> <pre><code>bl_id | name | bl_area | sum(paper_tons) | sum (bottles_tons) | paper_tons | bottles_tons </code></pre> <p><code>sum(paper_tons)</code> should return the sum of all the paper tons for the same <code>bl_id</code> like Jan to December.</p> <p>Using the below query i am able to retrieve all the data correctly except in the result, there are multiple occurances of <code>bl_ids(From bl_data table)</code>. </p> <pre><code>SELECT bl_main.bl_id,name,bl_area,sums.SummedPaper, sums.SummedBottles,paper_tons,bottles_tons FROM bl_main JOIN bl_details ON bl_main.bl_id= bl_details.bl_id left outer JOIN bl_data ON bl_data.bl_id= bl_main.bl_id left outer JOIN ( SELECT bl_id, SUM(Paper_tons) As SummedPaper, SUM(bottle_tons) As SummedBottles FROM bl_data </code></pre> <p>GROUP by bl_id) sums ON sums.bl_id = bl_main.bl_id</p> <p>I wanto retrieve only the unique values of bl_ids without repetition and it should contain the bl_id which has the max month and not all the months for the same bl_id. </p> <p>For ex: </p> <pre><code>INCORRECT **0601** University Hall 75.76 17051 1356 4040 1154 **11** **0601** University Hall 75.76 17051 1356 9190 101 **12** **0605** UIC Student 22.86 3331 14799 0 356 **8** CORRECT **0601** University Hall 75.76 17051 1356 9190 101 **12** **0605** UIC Student 22.86 3331 14799 0 356 **8** </code></pre> <p>I know I can get the max value using </p> <pre><code>WHERE Month = (SELECT MAX(Month) </code></pre> <p>but where exactlt should i add this in the query and should i change the join definition. Any help is highly appreciated as i am new to sql. Thanks in advance.</p>
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    1. COProofread your post and get your bl_id and bu_ids straight.
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    2. COWhich RDBMS are you using?
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    3. COBased on the fact that he's writing raw queries, I wouldn't think he's using RDBMS
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      1. USmarr75
 

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