Question

I am having trouble with some sql. When I run the following query:

Select * from teleapp;

I get TONS of results. Resulst which include a column (called cashwithappyn) that has TONS of empty or null data cells. (They look empty and don’t say null)

The column info is:

ColumnName      ID          Null? Data Type             Histogram   Num Distinct  Num Nulls    Density
CASHWITHAPPYN   54          Y     VARCHAR2(1 Byte)      Frequency   2             56895         0               

When I try to run the following query:

Select * from teleapp where cashwithappyn = null;

or

Select * from teleapp where cashwithappyn = '';

or

Select * from teleapp where cashwithappyn not like '';

or

Select * from teleapp where cashwithappyn not in ('Y','N');

or ANY type of combination, I cannot seem to get all of the rows with nothing in cashwithappyn.

Any ideas? Please help, this is the last part of a project that I was assigned to do and I just need to figure this out.

Thanks.

Answer 1

Maybe the column contains blanks. In that case you can do

WHERE TRIM(CASHWITHAPYYN) IS NULL

TRIM removes all blanks before and after and if nothing is left anymore the value becomes NULL

e.g.

TRIM(' ') IS NULL -- one blank removed = true
TRIM(NULL)  IS NULL -- true

Also NULL cannot be compared with = NULL but must be phrased IS NULL. NULL is not a value as such and that is why the comparison never works.