我将如何在 php 中编写 sql 查询以获得此结果？

Question

First of all I am currently trying to learn php and I thought I would build a basic maintenance management app to better grasp everything I see in tutorials, and I hit a roadblock. I've been trying to get this to work following various tutorials online but I had no success so far, so I thought I would ask for help here. I really hope you can help me.

What I would like to know is how can I write the php & mysql to write the data from the first 3 table to the desired_table from below ?

Clients
------------------------------
client_id    | client_name
------------------------------  
    1        | client_1 
------------------------------  
    2        | client_2
------------------------------  
    3        | client_3 


Equipments
------------------------------
eq_id        | eq_name
------------------------------  
    1        | pc 
------------------------------  
    2        | laptop
------------------------------  
    3        | printer


Operations
------------------------------------------------
op_id        | op_desc
------------------------------------------------    
    1        | dust cleaning
------------------------------------------------    
    2        | changing processor cooling paste
------------------------------------------------    
    3        | cpu replacement
------------------------------------------------    
    4        | display replacement
------------------------------------------------    
    5        | dvd-rom replacement
------------------------------------------------    
    6        | ram replacement
------------------------------------------------    
    7        | cartrige replacement



Desired_table
-------------------------------------
id  | client_id  | eq_id  | op_id  |
-------------------------------------   
  1 |    1       |    1   |   1    |
-------------------------------------
  2 |    1       |    1   |   2    |
-------------------------------------   
  3 |    1       |    1   |   3    |
-------------------------------------   
  4 |    1       |    1   |   5    |
-------------------------------------   
  5 |    1       |    2   |   1    |
-------------------------------------   
  6 |    1       |    2   |   2    |
-------------------------------------   
  7 |    1       |    2   |   4    |
-------------------------------------   
  8 |    2       |    1   |   1    |
-------------------------------------   
  9 |    2       |    1   |   2    |
-------------------------------------   
  10|    2       |    1   |   3    |
-------------------------------------   
  11|    2       |    1   |   5    |
-------------------------------------   
  12|    2       |    3   |   1    |
-------------------------------------   
  13|    2       |    3   |   7    |

I thought I would have a form with input fields for the client data and the equipment data and operations data I would have in dropdowns. When I would select an equipment a new dropdown would appear with the operations, and then submit it.

Hope this doesn't get marked as too broad subject :)

Answer 1

Using the code from your bitbucket this should do it:

$page = $db->prepare("
    INSERT INTO new_table_name (column_name1, column_name2, column_name3) 
    VALUES (:col1, :col2, :col3)
");

$page->bindparam(':col1', $value1);
$page->bindparam(':col2', $value2);
$page->bindparam(':col3', $value3);
$page->execute();
if($page->rowcount() > 0){
    echo "Inserted a new row";
}

Here is a example, replace 'new_table_name' to the name off the new table and change the column names.

After that simiply change $value1, 2 and 3 to the variables that contain the value you want to insert and you're good to go.

If you want to know if the insert was succesful just check with $page->rowcount(). If the rowcount is more than 0 it was succesful.

And just to clarify, this is called a prepared statement if you don't know this yet. What the code does is this:

• Prepare tells the server what you're planning to do. This adds a really strong layer off protection since basic sql injection are close to impossible to do.

• After that you bind the variables to the given parameters (Other syntax is possible, I just prefer this one). The code takes care off quotations so just put the parameter in there.

• Execute the actual query

And just for good measure, you can add 2 extra parameters to bindparam. In the third you can define a variable type, PDO::PARAM_STR and PDO::PARAM_INT block any other type off variable. The 4th lets you set a max length, if the variable is longer it will get blocked.

This will look like this:

$page->bindparam(':col1', $value1, PDO::PARAM_STR, 100);
//block anything which isn't a string or longer than 100 characters