public override DbExpression Visit(DbEqualExpression exp)
{
DbExpression left = exp.Left;
DbExpression right = exp.Right;
left = DbExpressionHelper.OptimizeDbExpression(left);
right = DbExpressionHelper.OptimizeDbExpression(right);
//明确 left right 其中一边一定为 null
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(right))
{
left.Accept(this);
this._sqlBuilder.Append(" IS NULL");
return(exp);
}
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(left))
{
right.Accept(this);
this._sqlBuilder.Append(" IS NULL");
return(exp);
}
AmendDbInfo(left, right);
left.Accept(this);
this._sqlBuilder.Append(" = ");
right.Accept(this);
return(exp);
}
static void Method_Sql_Equals(DbMethodCallExpression exp, SqlGenerator generator)
{
DbExpression left = exp.Arguments[0];
DbExpression right = exp.Arguments[1];
left = DbExpressionHelper.OptimizeDbExpression(left);
right = DbExpressionHelper.OptimizeDbExpression(right);
//明确 left right 其中一边一定为 null
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(right))
{
left.Accept(generator);
generator._sqlBuilder.Append(" IS NULL");
return;
}
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(left))
{
right.Accept(generator);
generator._sqlBuilder.Append(" IS NULL");
return;
}
AmendDbInfo(left, right);
left.Accept(generator);
generator._sqlBuilder.Append(" = ");
right.Accept(generator);
return;
}
public void Process(DbMethodCallExpression exp, SqlGenerator generator)
{
DbExpression left = exp.Arguments[0];
DbExpression right = exp.Arguments[1];
left = DbExpressionExtension.StripInvalidConvert(left);
right = DbExpressionExtension.StripInvalidConvert(right);
//明确 left right 其中一边一定为 null
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(right))
{
left.Accept(generator);
generator.SqlBuilder.Append(" IS NOT NULL");
return;
}
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(left))
{
right.Accept(generator);
generator.SqlBuilder.Append(" IS NOT NULL");
return;
}
SqlGenerator.AmendDbInfo(left, right);
left.Accept(generator);
generator.SqlBuilder.Append(" <> ");
right.Accept(generator);
}
static void Method_NotEquals(DbMethodCallExpression exp, SqlGenerator generator)
{
MethodInfo method = exp.Method;
if (method.DeclaringType != UtilConstants.TypeOfSql)
{
throw UtilExceptions.NotSupportedMethod(method);
}
DbExpression left = exp.Arguments[0];
DbExpression right = exp.Arguments[1];
left = DbExpressionHelper.OptimizeDbExpression(left);
right = DbExpressionHelper.OptimizeDbExpression(right);
//明确 left right 其中一边一定为 null
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(right))
{
left.Accept(generator);
generator._sqlBuilder.Append(" IS NOT NULL");
return;
}
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(left))
{
right.Accept(generator);
generator._sqlBuilder.Append(" IS NOT NULL");
return;
}
AmendDbInfo(left, right);
left.Accept(generator);
generator._sqlBuilder.Append(" <> ");
right.Accept(generator);
return;
}
public override DbExpression Visit(DbNotEqualExpression exp)
{
DbExpression left = exp.Left;
DbExpression right = exp.Right;
left = DbExpressionExtension.StripInvalidConvert(left);
right = DbExpressionExtension.StripInvalidConvert(right);
MethodInfo method_Sql_NotEquals = UtilConstants.MethodInfo_Sql_NotEquals.MakeGenericMethod(left.Type);
/* Sql.NotEquals(left, right) */
DbMethodCallExpression left_not_equals_right = DbExpression.MethodCall(null, method_Sql_NotEquals, new List <DbExpression>(2)
{
left, right
});
//明确 left right 其中一边一定为 null
if (DbExpressionExtension.AffirmExpressionRetValueIsNull(right) || DbExpressionExtension.AffirmExpressionRetValueIsNull(left))
{
/*
* a.Name != null --> a.Name != null
*/
left_not_equals_right.Accept(this);
return(exp);
}
if (right.NodeType == DbExpressionType.SubQuery || left.NodeType == DbExpressionType.SubQuery)
{
/*
* a.Id != (select top 1 T.Id from T) --> a.Id <> (select top 1 T.Id from T)，对于这种查询，我们不考虑 null
*/
left_not_equals_right.Accept(this);
return(exp);
}
MethodInfo method_Sql_Equals = UtilConstants.MethodInfo_Sql_Equals.MakeGenericMethod(left.Type);
if (left.NodeType == DbExpressionType.Parameter || left.NodeType == DbExpressionType.Constant)
{
var t = right;
right = left;
left = t;
}
if (right.NodeType == DbExpressionType.Parameter || right.NodeType == DbExpressionType.Constant)
{
/*
* 走到这说明 name 不可能为 null
* a.Name != name --> a.Name <> name or a.Name is null
*/
if (left.NodeType != DbExpressionType.Parameter && left.NodeType != DbExpressionType.Constant)
{
/*
* a.Name != name --> a.Name <> name or a.Name is null
*/
/* Sql.Equals(left, null) */
var left_is_null1 = DbExpression.MethodCall(null, method_Sql_Equals, new List <DbExpression>(2)
{
left, DbExpression.Constant(null, left.Type)
});
/* Sql.NotEquals(left, right) || Sql.Equals(left, null) */
var left_not_equals_right_or_left_is_null = DbExpression.Or(left_not_equals_right, left_is_null1);
left_not_equals_right_or_left_is_null.Accept(this);
}
else
{
/*
* name != name1 --> name <> name，其中 name 和 name1 都为变量且都不可能为 null
*/
left_not_equals_right.Accept(this);
}
return(exp);
}
/*
* a.Name != a.XName --> a.Name <> a.XName or (a.Name is null and a.XName is not null) or (a.Name is not null and a.XName is null)
* ## a.Name != a.XName 不能翻译成：not (a.Name == a.XName or (a.Name is null and a.XName is null))，因为数据库里的 not 有时候并非真正意义上的“取反”！
* 当 a.Name 或者 a.XName 其中一个字段有为 NULL，另一个字段有值时，会查不出此条数据 ##
*/
DbConstantExpression null_Constant = DbExpression.Constant(null, left.Type);
/* Sql.Equals(left, null) */
var left_is_null = DbExpression.MethodCall(null, method_Sql_Equals, new List <DbExpression>(2)
{
left, null_Constant
});
/* Sql.NotEquals(left, null) */
var left_is_not_null = DbExpression.MethodCall(null, method_Sql_NotEquals, new List <DbExpression>(2)
{
left, null_Constant
});
/* Sql.Equals(right, null) */
var right_is_null = DbExpression.MethodCall(null, method_Sql_Equals, new List <DbExpression>(2)
{
right, null_Constant
});
/* Sql.NotEquals(right, null) */
var right_is_not_null = DbExpression.MethodCall(null, method_Sql_NotEquals, new List <DbExpression>(2)
{
right, null_Constant
});
/* Sql.Equals(left, null) && Sql.NotEquals(right, null) */
var left_is_null_and_right_is_not_null = DbExpression.And(left_is_null, right_is_not_null);
/* Sql.NotEquals(left, null) && Sql.Equals(right, null) */
var left_is_not_null_and_right_is_null = DbExpression.And(left_is_not_null, right_is_null);
/* (Sql.Equals(left, null) && Sql.NotEquals(right, null)) || (Sql.NotEquals(left, null) && Sql.Equals(right, null)) */
var left_is_null_and_right_is_not_null_or_left_is_not_null_and_right_is_null = DbExpression.Or(left_is_null_and_right_is_not_null, left_is_not_null_and_right_is_null);
/* Sql.NotEquals(left, right) || (Sql.Equals(left, null) && Sql.NotEquals(right, null)) || (Sql.NotEquals(left, null) && Sql.Equals(right, null)) */
var e = DbExpression.Or(left_not_equals_right, left_is_null_and_right_is_not_null_or_left_is_not_null_and_right_is_null);
e.Accept(this);
return(exp);
}