Sunday, October 3, 2010

which is faster ? select * from table or select 'all Columns' from table ??

Many of us would have come across a scenario where  listing column names in select SQL  was found to be faster then using select * from table  command . This indeed is interesting .

The reason being ,

In case of using "select * from table" , A extra stage is added  where * is replaced by column names by teradata  and then it would fetch the data .

But using "select <all Columns > from table "  eliminates this extra stage of verifying and fetching on columns from the table.

Hence it is always recommended to use "select <all Columns > from table "

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