/**
  * Creates INNER JOIN SQL for associations.
  *
  * @param Table $from_table the table used for the FROM SQL statement
  * @param bool $using_through is this a THROUGH relationship?
  * @param string $alias a table alias for when a table is being joined twice
  * @return string SQL INNER JOIN fragment
  */
 public function constructInnerJoinSql(Table $from_table, $using_through = false, $alias = null)
 {
     if ($using_through) {
         $join_table = $from_table;
         $join_table_name = $from_table->getFullyQualifiedTableName();
         $from_table_name = Table::load($this->class_name)->getFullyQualifiedTableName();
     } else {
         $join_table = Table::load($this->class_name);
         $join_table_name = $join_table->getFullyQualifiedTableName();
         $from_table_name = $from_table->getFullyQualifiedTableName();
     }
     // need to flip the logic when the key is on the other table
     if ($this instanceof HasMany || $this instanceof HasOne) {
         $this->setKeys($from_table->class->getName());
         if ($using_through) {
             $foreign_key = $this->primary_key[0];
             $join_primary_key = $this->foreign_key[0];
         } else {
             $join_primary_key = $this->foreign_key[0];
             $foreign_key = $this->primary_key[0];
         }
     } else {
         $foreign_key = $this->foreign_key[0];
         $join_primary_key = $this->primary_key[0];
     }
     if (!\is_null($alias)) {
         $aliased_join_table_name = $alias = $this->getTable()->conn->quoteName($alias);
         $alias .= ' ';
     } else {
         $aliased_join_table_name = $join_table_name;
     }
     return "INNER JOIN {$join_table_name} {$alias}ON({$from_table_name}.{$foreign_key} = {$aliased_join_table_name}.{$join_primary_key})";
 }