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); }