asp.net - 搜索表格中的空字段

Question

我尝试了下面的命令。这是一个DataSource的 GridView它写在我的 .aspx 上页面，所以我不能使用像 "" 这样的字符或 '' .此代码不返回任何内容。我还尝试将 (string.empty, ""and null) 作为参数传递给 codebehind .什么都没用，我不知道还能做什么...

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"

Obs:我要过滤的字段 null他们是int32领域。(我知道 int32 不可能是 null )但我只是不知道该怎么做，所以我尝试了所有想到的方法。

Answer 1

此查询将始终不返回任何结果，因为您在此语句中使用了 INNER JOIN:

INNER JOIN responsaveis as resp ON ch.responsavel = resp.id

并使用 WHERE 语句将其中一个 INNER JOIN 文件与 NULL

进行比较

WHERE ch.responsavel IS NULL

INNER JOIN 连接 ONLY 非 NULL 的字段。所以这两个语句互不相干。