Added NULL flag for table columns

Author: santiescobares

src/main/java/net/escosoft/mysqlwrapper/table/TableColumn.java

@@ -12,7 +12,7 @@ public final class TableColumn {
     private final TableType type;
 
     private String[] typeData;
-    private boolean notNull;
+    private boolean Null, notNull;
     private String defaultValue;
 
     private TableColumn(String name, TableType type) {
@@ -38,6 +38,9 @@ public String create() {
                     .append(joiner)
                     .append(")");
         }
+        if (this.Null) {
+            builder.append(" NULL");
+        }
         if (this.notNull) {
             builder.append(" NOT NULL");
         }
@@ -65,6 +68,14 @@ public Builder typeData(String... typeData) {
             return this;
         }
 
+        /**
+         * Adds NULL string to current column building-up.
+         */
+        public Builder Null() {
+            this.column.Null = true;
+            return this;
+        }
+
         /**
          * Adds NOT NULL string to current column building-up.
          */