Tuesday, October 23, 2012

Teradata - Performace Tuning

Use group by instead of distinct because distinct occupies more spool space

Use EXISTS instead of IN because EXISTS stops the process once it finds the value

Join Columns of same datatype

Use UNION ALL instead of UNION

Remove secondary indexes when the data is being loaded,updated or deleted

Avoid correlated queries,cross join, product join

use Delete ALL - normal delete have rollback, for delete all there is no rollback(no transient journal overhead)

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