Using QGIS query builder

Question

I have only basic knowledge of using SQL code in QGIS. I am trying to use Query Builder to hide some specific line features. I have tried using =! and the id field reference for the particular features I want to hide but this results in zero features being selected. The column is text. I have tried creating a new column as text and identifying the fields I want as 'yes'and then writing a query identifying those fields not yes. I then did the same but this time as a integer but this doesn't work. Can anyone help. I'm sure its a simple task to do. Interestingly the text fields are all blank rather than null. How do you select a field that is empty

• Dirk: Do you use "Filter" to query your expression? Or did you try your expression from properties--> symbology...?
• Sean Jarrett: Hi Dirk I used query builder on the general tab in properties

Answer 1

The 'not equal to' operator in SQL is '<>' so you need to use:

OBJECTID <> 1

To select null fields you use:

IS NULL

To select text fields that are empty but not null try selecting an empty string '' or a string with a space ' ':

TextField = ''
TextField = ' '

• Sean Jarrett: Thanks for your suggestions. Is NULL works. What threw me was there is no operator option to use IS so my lack of programming knowledge didn't allow me to 'get creative'. Thanks again