Question

目前我有三个这样的查询：

var query1 = (from a in dbContext.Table1 
              where a.email == someEmail 
              select a.Table1K).ToList();
var query2 = (from a in dbContext.Table2 
              where a.emailAddrerss == someEmail 
              select a.Table2K).ToList();
var query3 = (from a in dbContext.Table3 
              where a.email == someEmail 
              select a.Table3K).ToList();

if ( query2.Any() || query3.Any() )
{
   return false;
}

if(query1.Count == 1 )
{
   var x = query1[0];
   // do some stuff with that x value ... 
}

有没有办法用外连接（我对外连接不是很好）我们可以在一个查询而不是三个查询中实现这个？

Answer 1

我不认为实际的加入是合适的，但你确实有一些改进的机会：

如果您只是想检查任何结果，请不要在查询2或3上调用ToList：

如果您只想从查询1中获取一个结果，请改为呼叫SingleOrDefault

var query1 = (from a in dbContext.Table1 
              where a.email == someEmail 
              select a.Table1K);
var query2 = (from a in dbContext.Table2 
              where a.emailAddrerss == someEmail 
              select a.Table2K);
var query3 = (from a in dbContext.Table3 
              where a.email == someEmail 
              select a.Table3K);


if ( query2.Any() || query3.Any() )
{
   return false;
}

var x = query1.SingleOrDefault();
if(x != null)
{
   // do some stuff with that x value ... 
}

将三个查询组合成一个外部联接

1 个答案: