Question

I have a table with 3 columns (containing Integer values that assume only values from 0 to 10). I want extract, with a single query, a table with 1 column. This column must assume a value based on the following logic:

1. If one of these three columns has value 0 —-> the value of column of table generated by query must be 0 too.

2. If none of the last three columns has value 0 —-> the value of column must assume the value 1.

Answer 1

You are looking for CASE construct or IF function:

SELECT CASE WHEN (t.field1 = 0 OR t.field2 = 0 OR t.field3 = 0) THEN 0
       ELSE 1 END AS value
FROM t;

In this specific case you might also use the fact that any member being zero will zero the product:

SELECT CASE WHEN (t.field1*t.field2*t.field3 = 0) THEN 0 ELSE 1 END AS value
FROM t;

Or

SELECT IF((t.field1*t.field2*t.field3)=0, 0, 1) AS value FROM t;