PDO insert into table with foreign keys - php

Question

I am having a few difficulties with mysql and PDO.
I wish to insert a product into the database, however the product table contains foreign keys. Naturally, I will not know the Foreign key ID when inserting. Am I doing this right??? Is there a better way of tackling this problem?
TABLE Products
Id PK AI int
Name Varchar(20)
CategoryId Int FK
TypeId Int FK
TABLE Categories
Id Int PK
Cat varchar(20)
TABLE Types
Id Int PK
Type varchar(20)
$type = 'Gloves';
$category = 'Clothing';
$sql = 'INSERT INTO Products
SET Name = :name, CategoryId = :catId, TypeId = :typeId
WHERE
CategoryId IN (SELECT Id FROM Categories WHERE Cat = :category) AND
TypeId IN (SELECT Id FROM Types WHERE Type = :type)'
$stmt = $db->prepare($sql);
$stmt->execute(array(':name' => 'Pink childrens gloves', ':category' => $category, ':type' => $type));
As mentioned in a comment below: Normally, I would be getting the ID from a select box. I cannot do this because it will be a script executing the query, not a user.

Answer 1

are you sure that this is what you want?
$sql = 'INSERT INTO Products
SET Name = :name
WHERE
CategoryId IN (SELECT Id FROM Categories WHERE Cat = :category) AND
TypeId IN (SELECT Id FROM Types WHERE Type = :type)'
I think you are trying to use UPDATE
$sql = 'UPDATE Products
SET Name = :name
WHERE
CategoryId IN (SELECT Id FROM Categories WHERE Cat = :category) AND
TypeId IN (SELECT Id FROM Types WHERE Type = :type)'

Answer 2

MySQL allows a combination of SELECT + INSERT in a single query:
INSERT INTO tbl_temp2 (fld_id)
SELECT tbl_temp1.fld_order_id
FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;
... but I wouldn't care about it. You cannot do proper error checking if you do three different things in a single query.
My advice is that you first validate that there're a category and a type that match the given names. In that step, you can easily get the corresponding IDs, which will let you perform a simple INSERT. Additionally, if you need to insert many products, you can validate first and once.

Answer 3

In addition to #Álvaro G. Vicario's answer, you can also do something like (works in normal sql, I have not tried it with bound variables):
$sql = 'INSERT INTO Products
SET Name = :name,
CategoryId = (SELECT Id FROM Categories WHERE Cat = :category),
TypeId = (SELECT Id FROM Types WHERE Type = :type)';
But I would always check for existing categories and types first, insert where necessary and get the required id's as this will lead to unexpected results if there are no matches in the inner selects.

Answer 4

First of all you need to figure out which is the table that have foreign key data.
Then you need to get all possible values from foreign key table.
Finally you need to build and drop-down list or similar to give ability of select acceptable foreign key.
$q=$db->prepare('SELECT ke.referenced_table_name assoc_table,
ke.referenced_column_name assoc_col FROM
information_schema.KEY_COLUMN_USAGE ke WHERE ke.referenced_table_name IS NOT NULL
AND ke.table_schema=:database AND ke.table_name=:tablename AND ke.column_name=:col');
$q->bindValue(':database','mydatabasename'); //Set your database name here
$q->bindValue(':tablename','Departments'); //Set your table name here
$q->bindValue(':col','City'); //Set the column which foreign key values you want to have here
if($q->execute()) {
$foreingtable=$q->fetch(PDO::FETCH_ASSOC);
$q=$db->prepare('SELECT '.$foreingtable['assoc_col'].' FROM '.$foreingtable['assoc_table']);
if($q->execute())
echo json_encode($q->fetchAll(PDO::FETCH_COLUMN));
}
else {
header('http/1.1 500 Internal Server Error');
print_r($q->errorInfo());
exit;
}
More about this: Get list of possible foreign key values in MySql using PDO