Question

I built two tables with the following SQL:

CREATE TABLE state(
   IDstate INTEGER not null auto_increment,
   state_name VARCHAR(40) not null,
   UNIQUE(state_name),
   CONSTRAINT IDstate PRIMARY KEY(IDstate)
)auto_increment=100;

CREATE TABLE city(
   IDcity INTEGER not null auto_increment,
   city_name VARCHAR(60) not null,
   IDstate INTEGER not null,
   CONSTRAINT IDcity PRIMARY KEY(IDcity),
   CONSTRAINT IDstate FOREIGN KEY(IDstate) REFERENCES state(IDstate)
)auto_increment=100;

I want to create a function with PHP-PDO-MySQL, I am sure about the next:

1. My function receives two parameters: $state, $city.

2. I have to avoid the repetition of values.

   $dbcon=new PDO('mysql:host=localhost; dbname=hotel','root', '');
   $sql = "SELECT IDstate FROM state WHERE state_name=:state_name";
   $query = $dbcon->prepare($sql);
   $query->execute(array(':state_name'=>$state_name));
   $array = $query->fetchAll();
   if ($query->rowCount() == 0){
     $sql = "INSERT INTO state (state_name) VALUES (:state_name);";
     $query = $dbcon->prepare($sql);
     $query->execute(array(':state_name'=>$state_name));
     $sql = "INSERT INTO city (city_name, IDstate) VALUES (:city_name, :IDstate);";
     $query = $dbcon->prepare($sql);
     $query->execute(array(':city_name'=>$city_name, ':IDstate'=>$dbcon->lastInsertId()));
   } else {
     $IDstate = $array[0]['IDstate'];
     $sql = "INSERT INTO city (city_name, IDstate) VALUES (:city_name, :IDstate)";
     $query = $dbcon->prepare($sql);
     $query->execute(array(':city_name'=>$city_name, ':IDstate'=>$IDstate));
     print_r($query->rowCount());
   }
   

I need to cover the following options:

1. Insert new both state and city.
2. Insert new city for an existing state.
3. Avoid insert for both existing state and city.

The code above works fine, but I’d like improve it. I was reading about the best option is to write a transaction instead of the previous code.

On the other hand, I need to add a third table, maybe a fourth table, I think I am repeating a lot of code: boilerplate coding.

I would like your opinions and advice.

Answer 1

So, this may not fully answer your question, but here are my thoughts:

• if it works, don’t fix it.
• What engine are you using? If you are using MySQL’s MyISAM tables, it will not support transactions and will not return an error.
• Depending on how much volume you are expecting, what you have shouldn’t be too slow.
• Add a limit to your select, since you’re only getting 1 state name. Limits have a big performance increase.
• The longest US state name is 13 characters, not 40