Search for empty fields on a table

[coormub]

I tried the command below. It's a \[code\]DataSource\[/code\] of a \[code\]GridView\[/code\] and it's written on my \[code\].aspx\[/code\] page, so I can not use characters like \[code\]""\[/code\] or \[code\]''\[/code\]. This code does not return me anything. I also tried to pass (string.empty, "" and null) as parameters in the \[code\]codebehind\[/code\]. Nothing worked and I don't know what else to do...\[code\]SelectCommand="SELECT ch.id, sit.descricao as situacao, resp.responsavel, ch.dt_cadastro, ch.previsao_termino, func.descricao as funcionalidade, proj.descricao as projeto ,pr.id as prid, pr.prioridade, clb.clube FROM chamados AS ch INNER JOIN prioridades as pr ON ch.prioridade = pr.id INNER JOIN clubes as clb ON ch.clube = clb.id INNER JOIN responsaveis as resp ON ch.responsavel = resp.id INNER JOIN situacoes as sit ON ch.situacao = sit.id INNER JOIN projetos as proj ON ch.projeto = proj.id INNER JOIN funcionalidades as func ON ch.funcionalidade = func.id WHERE ch.responsavel IS NULL"\[/code\]\[code\]Obs:\[/code\]the field I want to filter as \[code\]null\[/code\] they are \[code\]int32\[/code\] fields.( I know that \[code\]int32\[/code\] can't be \[code\]null\[/code\]) But I just didn't know what to do, so I tried everything that came to mind.