NOT LIKE and LIKE not returning opposite result

Does this return the correct result ?

Select * from tbl1 WHERE COALESCE([TextCol],'-1') NOT LIKE '%TAX%'

I believe NULL values are the issue here, if the column contains them, then NULL NOT LIKE '%TAX%' will return UNKNOWN/NULL and therefore won’t be selected.

I advise you to read about handling with NULL values , or here.

As @ughai suggested, if performance is an issue you can also use:

  Select * from tbl1 
  WHERE [TextCol] NOT LIKE '%TAX%'
     OR [TextCol] IS NULL