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POWhy have I got an increased row count after LEFT JOIN
 

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  1. POWhy have I got an increased row count after LEFT JOIN
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    <p>Im trying to JOIN together various datasets to get a master table, though I managed to preserve the row count after 3 left joins, but after the next step, it seems to increase it. Any ideas why?</p> <p>Query with 3 Joins</p> <pre><code>------------------------------------------------------------------- --- STEP 4: ---------------- ------------------------------------------------------------------- SELECT DISTINCT Table1.[Field1] , Table1.[Field2] , Table3.[Field3] , Table1.[Field4] , Table1.[Field5] , Table1.[Field6] , Table1.[Field7] , Table1.[Field8] , Table1.[Field9] , Table1.[Field10] FROM db1.dbo.raw_tbl_1 AS Table1 LEFT JOIN db2.dbo.tbl_2 Table2 ON Table1.Field7 = Table2.[Field13] LEFT JOIN db2.dbo.tbl_3 Table3 ON CONVERT(INT,Table1.[Field2]) = Table3.Field14 LEFT JOIN db2.dbo.tbl_4Table4 ON Table2.Field17= Table4. Field15 WHERE Table2. Field17 IS NOT NULL -- 2682270 rows (Desired row count) </code></pre> <p>Query with 4 Joins (The one that increases row count)</p> <pre><code>------------------------------------------------------------------- --- STEP 5: ---- ------------------------------------------------------------------- SELECT DISTINCT Table1.[Field1] , Table1.[Field2] , Table3.[Field3] , Table1.[Field4] , Table1.[Field5] , Table1.[Field6] , Table1.[Field7] , Table5.[Field11] , Table6.[Field12] , Table1.[Field8] , Table1.[Field9] , Table1.[Field10] FROM db1.dbo.raw_tbl_1 AS Table1 LEFT JOIN db2.dbo.tbl_2 Table2 ON Table1.Field7 = Table2.[Field13] LEFT JOIN db2.dbo.tbl_3 Table3 ON CONVERT(INT,Table1.[Field2]) = Table3. Field14 LEFT JOIN db2.dbo.tbl_4 Table4 ON Table2. Field17= Table4. Field15 LEFT JOIN db2.dbo.tbl_5 Table5 ON Table4. Field18= Table5. Field16 LEFT JOIN db2.dbo.tbl_6 Table6 ON Table5.[Field11] = CONVERT(INT,Table6.[Table6]) WHERE Table2.Field17 IS NOT NULL </code></pre>
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    1. USAndriy M
    1. USVishalJ
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    1. CObecause of a 1-many relationship.
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      1. POWhy have I got an increased row count after LEFT JOIN
      1. USJodrell
 

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