Question

I’m building a file, using SSMS, that will be an input to a machine learning program. The output file will be the result of a query of several tables in a SQL Server 2008 R2 Express DB.

The query results in NULL values for some of the cells. Currently I’m using the ISNULL() function to insert '0.00' when there is a NULL value but this is just a temporary measure as some values are actually '0.00' and this skews the calculation.

What raw data would look like:

  id        surveyResponseRate      personResponseRate
 001            .068                      .15
 002            0.00                     NULL
 003            .014                      .03
 004            NULL                      .20
 005            .068                     0.00
 ...             ...                      ...

What current process creates:

 id        surveyResponseRate      personResponseRate
 001            .068                      .15
 002            0.00                     0.00
 003            .014                      .03
 004            0.00                      .20
 005            .068                     0.00
 ...             ...                      ...

I’m curious if there’s a way to create a binary column that is 0 if the value is actually 0.00 and 1 if it’s actually 0.00 due a NULL value.

What I’d like to see:

 id        surveyResponseRate      personResponseRate  survRRNA      perRRNA
 001            .068                      .15              0            0
 002            0.00                     0.00              0            1
 003            .014                      .03              0            0
 004            0.00                      .20              1            0
 005            .068                     0.00              0            0
 ...             ...                      ...             ...          ...

Any suggestions for how to do this?

Answer 1

Just add expressions for the new columns to the SELECT clause like this:

SELECT
  id,
  ISNULL(surveyResponseRate, 0) AS surveyResponseRate,
  ISNULL(personResponseRate, 0) AS personResponseRate,
  CASE WHEN surveyResponseRate IS NULL THEN 1 ELSE 0 END AS survRRNA,
  CASE WHEN personResponseRate IS NULL THEN 1 ELSE 0 END AS perRRNA
FROM ...