Fix issue of missing comma between joins in subjoin

Author: tomershay

src/main/java/net/sf/jsqlparser/statement/select/Join.java

@@ -195,7 +195,7 @@ public String toString() {
         if (isSimple() && isOuter()) {
             return "OUTER " + rightItem;
         } else if (isSimple()) {
-            return ", " + rightItem;
+            return "" + rightItem;
         } else {
             String type = "";
 

src/main/java/net/sf/jsqlparser/statement/select/SubJoin.java

@@ -65,7 +65,11 @@ public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append("(").append(left);
         for (Join j : joinList) {
-            sb.append(j.isSimple() ? "" : " ").append(j);
+            if (j.isSimple()) {
+                sb.append(", ").append(j);
+            } else {
+                sb.append(" ").append(j);
+            }
         }
 
         sb.append(")").append((alias != null) ? (" " + alias.toString()) : "").append((pivot != null) ? " " + pivot : "");