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Performance LOAD; SQL SELECT

Hello everyone,

Is there a difference in terms of performance in doing :

LOAD

A,

B;

SQL SELECT *

FROM ..

or

LOAD

A,

B;

SQL SELECT A,B

FROM...

Let's say the table has a lot of fields.

Thank you.

Have a good day.

Laura

6 Replies
jerrysvensson
Valued Contributor II

Re: Performance LOAD; SQL SELECT

Yes there could be a huge difference if your table has like 100 fields.

datanibbler
Esteemed Contributor

Re: Performance LOAD; SQL SELECT

Hi Laura,

I'd say the performance should logically be bettter if, out of a lot of fields in the database_table, you SELECT only the fields that you need. The difference is probably not too much, though, as the preceding LOAD takes only those two fields ...

giakoum
Honored Contributor II

Re: Performance LOAD; SQL SELECT

especially if large text fields are included

jerrysvensson
Valued Contributor II

Re: Performance LOAD; SQL SELECT

I have seen data loads go from one hour (Select *) to five minutes (Select A,B). We had a table with 170 fields.

neetha_p
Honored Contributor

Re: Performance LOAD; SQL SELECT

Hi,

There will be huge difference between Getting  two fields and 100's of fields from database in terms of performance.

As SQL SELECT statement does Implicit LOAD.

Regards

Neetha

hrlinder
Honored Contributor

Re: Performance LOAD; SQL SELECT

additionally to existing answers there is another aspect

Select * requires a full table scan which takes time

select a,b might take use of an index which is much faster

in our case we dropped the load time from 1hour to 5 minutes (select * got 6 fields, later we used select with 2 fields)!

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