What is the default join strategy in Teradata???
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Answer / dg
The Teradata Cost based optimizer will decide the join
strategy based on the optimum path. The common startegies
followed are from Merge, Hash & Nested Join
| Is This Answer Correct ? | 25 Yes | 3 No |
Answer / yuvaevergreen
Three strategies followed by optimizer are:
1.Duplication of rows of one table to every amp
--> This one is opted by optimizer when the non-PI column
is on a small table.
2.Redistribution of the non PI rows of the table to the amp
containing the matching PI row amp.
--> This one is opted when the tables are large. The non PI
column is in one table is redistributed to the amp
containing the matching PI.
3.Redistribute both the rows of the table by hash values.
--> This is chosen when the join is on a column that is not
the PI in either table. This will require the most spool
space.
| Is This Answer Correct ? | 13 Yes | 3 No |
Answer / tdguy
i think there is no "default" join strategy. Optimizer
decides the type of strategy based on the best retrieval
path and other parameters to execute the query. Merge join
strategy, nested join strategy, hash join strategy and
product join strategies are the common strategies followed
by TD.
| Is This Answer Correct ? | 7 Yes | 1 No |
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