DSXchange

Can Datastage 7.5.2 read views from Source tables?

Yes. But the cost of materializing the view may be one that you wish to avoid.

ray.wurlod wrote:Yes. But the cost of materializing the view may be one that you wish to avoid. ...

Please tell me why Cost will be high?

Imagine that the SELECT statement that defines the view selects 10 million rows, and when you select from the view you want only 10,000 of these.

Selecting from the view means that the first, large, SELECT has to occur to materialize the view, and only then can your second, small, SELECT proceed.

If you had selected the 10,000 rows from the base table, only the small SELECT would need to be executed.

ray.wurlod wrote:Imagine that the SELECT statement that defines the view selects 10 million rows, and when you select from the view you want only 10,000 of these.

Selecting from the view means that the first, large ...

Thanks Ray ......the info is really informative