Debug: Add SQL generation logging directly in SQL generators

Added Console.WriteLine logging in:
- MySqlUpdateSqlGenerator.AppendUpdateOperation: Logs UPDATE SQL as it's generated
- MySqlQuerySqlGenerator.VisitSelect: Logs SELECT query info and partial SQL

This will capture the actual malformed SQL queries directly during generation,
showing the empty columns that cause the "near ', ,'" syntax errors.

Co-authored-by: renemadsen <76994+renemadsen@users.noreply.github.com>

Author: Copilot

src/EFCore.MySql/Query/ExpressionVisitors/Internal/MySqlQuerySqlGenerator.cs

@@ -1023,5 +1023,22 @@ protected override void CheckComposableSql(string sql)
             // MySQL supports CTE (WITH) expressions within subqueries, as well as others,
             // so we allow any raw SQL to be composed over.
         }
+
+        protected override Expression VisitSelect(SelectExpression selectExpression)
+        {
+            Console.WriteLine($"[DEBUG SQL] VisitSelect called - Tables: {selectExpression.Tables.Count}, Projection: {selectExpression.Projection.Count}");
+            var result = base.VisitSelect(selectExpression);
+            
+            // Log current SQL state after SELECT is generated
+            var currentSql = Sql.ToString();
+            var lastSelect = currentSql.LastIndexOf("SELECT");
+            if (lastSelect >= 0)
+            {
+                var sqlFragment = currentSql.Substring(lastSelect, Math.Min(200, currentSql.Length - lastSelect));
+                Console.WriteLine($"[DEBUG SQL] After VisitSelect: {sqlFragment}");
+            }
+            
+            return result;
+        }
     }
 }

src/EFCore.MySql/Update/Internal/MySqlUpdateSqlGenerator.cs

@@ -181,9 +181,20 @@ public override ResultSetMapping AppendUpdateOperation(
             IReadOnlyModificationCommand command,
             int commandPosition,
             out bool requiresTransaction)
-            => _options.ServerVersion.Supports.Returning
+        {
+            var startLength = commandStringBuilder.Length;
+            var result = _options.ServerVersion.Supports.Returning
                 ? AppendUpdateReturningOperation(commandStringBuilder, command, commandPosition, out requiresTransaction)
                 : base.AppendUpdateOperation(commandStringBuilder, command, commandPosition, out requiresTransaction);
+            
+            // Debug: Log the generated SQL
+            var generatedSql = commandStringBuilder.ToString(startLength, commandStringBuilder.Length - startLength);
+            Console.WriteLine($"[DEBUG SQL Generated] AppendUpdateOperation:");
+            Console.WriteLine(generatedSql);
+            Console.WriteLine($"[DEBUG SQL Generated] Table: {command.TableName}, Columns: {command.ColumnModifications.Count}");
+            
+            return result;
+        }
 
         /// <summary>
         /// Appends SQL for updating a row to the commands being built, via an UPDATE containing a RETURNING clause