How to efficiently use try catch blocks in PHP

Question

I was using try..catch blocks in my PHP code for some time now but I don't know if the way I was using it is correct. 
For example:

 try {
      $tableAresults = $dbHandler->doSomethingWithTableA();
      $tableBresults = $dbHandler->doSomethingElseWithTableB();
 } catch (Exception $e) {
      return $e;
 }

I think this above method is better than this:
 
 try {
       $tableAresults = $dbHandler->doSomethingWithTableA();
 } catch (Exception $e) {
       return $e;
 }
 try {
       $tableBresults = $dbHandler->doSomethingWithTableB();
 } catch (Exception $e) {
       return $e;
 }

I did the first code so as to group multiple database operations in the same try/catch block. Is this a good practice? Is there any advantage of using try/catch blocks per database transaction?