PostgreSQL: How to modify values in view

Question

I have a table I don't want to touch, but from this table I want to create many views that will serve different purposes/analyses.

In one case, I need to change a value based on a condition (-1 become some positive value).

Is it even possible to do that in PostgreSQL?

For example, -1 in the table will become 1 in the view if Col3='B':

+------+------+------+    +------+------+------+
| Col1 | Col2 | Col3 |    | Col1 | Col2 | Col3 |
+------+------+------+ >  +------+------+------+
|    1 |  3.5 | A    | >  |    1 |  3.5 | A    |
|    2 |   -1 | B    | >  |    2 |    1 | B    |
|    3 |   -1 | A    |    |    3 |   -1 | A    |
+------+------+------+    +------+------+------+

Gordon Linoff · Accepted Answer · 2021-09-22 12:50:13Z

1

You need to modify the view an put the logic in the query:

select col1,
       (case when col3 = 'B' and col2 = -1 then 1 else col2 end) as col2,
       col3
from . . .

answered Sep 22, 2021 at 12:50

Gordon Linoff

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