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chreez

Query Efficiency

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Sample Table


| id    |  date            | time      | ref  

|  0    |    10/10/10   | 9:51      |    2

|  1    |    10/10/10   | 9:52      |    2

|  2    |    10/10/10   | 9:53      |    4

|  3    |    10/10/11   | 9:54      |    3

|  4    |    10/10/11   | 9:55      |    4

|  5    |    10/10/11   | 9:56      |    2

 

I need to get each row where ref != id and then get the row where date, time is greatest.

 

Example output


| id    |  date            | time       | ref  

|  2    |    10/10/10   |  9:53      |    4

|  5    |    10/10/11   |  9:56      |    2

 

The results have ref != id and other rows where ref != id are eliminated because they have lesser values in date, time.

 

What is the best way to do this

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