Fix SQL output binding for native json data type columns

src/SqlAsyncCollector.cs

@@ -501,13 +501,17 @@ public static string GetColumnDefinitionsQuery(SqlObject table)
             {
                 return $@"
                     select
-	                    {ColumnName}, DATA_TYPE +
+	                    {ColumnName},
 		                    case
-			                    when CHARACTER_MAXIMUM_LENGTH = -1 then '(max)'
-			                    when CHARACTER_MAXIMUM_LENGTH <> -1 then '(' + cast(CHARACTER_MAXIMUM_LENGTH as varchar(4)) + ')'
-                                when DATETIME_PRECISION is not null and DATA_TYPE not in ('datetime', 'date', 'smalldatetime') then '(' + cast(DATETIME_PRECISION as varchar(1)) + ')'
-			                    when DATA_TYPE in ('decimal', 'numeric') then '(' + cast(NUMERIC_PRECISION as varchar(9)) + ',' + + cast(NUMERIC_SCALE as varchar(9)) + ')'
-			                    else ''
+			                    when DATA_TYPE = 'json' then 'nvarchar(max)'
+			                    else DATA_TYPE +
+				                    case
+					                    when CHARACTER_MAXIMUM_LENGTH = -1 then '(max)'
+					                    when CHARACTER_MAXIMUM_LENGTH <> -1 then '(' + cast(CHARACTER_MAXIMUM_LENGTH as varchar(4)) + ')'
+					                    when DATETIME_PRECISION is not null and DATA_TYPE not in ('datetime', 'date', 'smalldatetime') then '(' + cast(DATETIME_PRECISION as varchar(1)) + ')'
+					                    when DATA_TYPE in ('decimal', 'numeric') then '(' + cast(NUMERIC_PRECISION as varchar(9)) + ',' + + cast(NUMERIC_SCALE as varchar(9)) + ')'
+					                    else ''
+				                    end
 		                    end as {ColumnDefinition}
                     from
 	                    INFORMATION_SCHEMA.COLUMNS c

test/Unit/SqlOutputBindingTests.cs

@@ -70,5 +70,22 @@ public void TestAsBracketQuotedString(string s, string expectedResult)
             string result = s.AsBracketQuotedString();
             Assert.Equal(expectedResult, result);
         }
+
+        /// <summary>
+        /// Verifies that the column definitions query maps JSON columns to nvarchar(max) instead of
+        /// the invalid json(max) syntax. The native json data type does not accept a length specifier.
+        /// See: https://learn.microsoft.com/en-us/sql/t-sql/data-types/json-data-type
+        /// </summary>
+        [Fact]
+        public void TestGetColumnDefinitionsQueryMapsJsonToNvarcharMax()
+        {
+            var table = new SqlObject("dbo.TestTable");
+            string query = SqlAsyncCollector<string>.TableInformation.GetColumnDefinitionsQuery(table);
+
+            // The query should map json columns to nvarchar(max)
+            Assert.Contains("when DATA_TYPE = 'json' then 'nvarchar(max)'", query);
+            // The query should not produce 'json(max)' which is invalid SQL syntax
+            Assert.DoesNotContain("json(max)", query);
+        }
     }
 }