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MMMY
Starting Member
14 Posts |
 Posted - 2012-08-15 : 19:03:09
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| Updating a table... Which would be faster? Or is there an even better option? Thanks!QUERY 1Update ASet A.1 = B.1,A.2 = B.2From AJoin B on A.3 = B.3QUERY 2Update ASet A.1 = (Select B.1 From B Where A.3 = B.3),A.2 = (Select B.2 From B Where A.3 = B.3) |
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chadmat
The Chadinator
1974 Posts |
Posted - 2012-08-15 : 19:06:06
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| I suspect Query 1 would be faster (Query 2 isn't a valid query, but I get what you mean)-Chad |
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SwePeso
Patron Saint of Lost Yaks
30421 Posts |
Posted - 2012-08-16 : 03:25:31
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There is a logical difference between the two queries.If there is no match between A table and B table; with query 2 the old values for colunms 1 and 2 remains the same as before.With Query 2 (if there is no match) the values are replaced with a NULL values.Query 2 also have the risk for failure if there are more than 1 match between table A and B.
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JOIN vs NESTED SQL: Which is faster?