How to get primary key name on laravel query builder - database

Question

Is there a way to get a table's primary key name using the Laravel query builder? Can i do something like
$key = DB::table($someTable)->getPrimaryKey();
I've looked through the documentation and API but couldn't find any reference to it.
Thanks in advance.

Answer 1

You can get an array of indexes for a table directly using the Schema manager:
$indexes = DB::connection()->getDoctrineSchemaManager()->listTableIndexes($table);
OR
$indexes = Schema::getConnection()->getDoctrineSchemaManager()->listTableIndexes($table);
And then you can get an array of the columns associated with that index key:
$columns = $indexes[ 'primary' ]->getColumns();
This function can be used to find the primary key(s) or unique key(s) for a table you know nothing about:
public function getTablePrimaryOrUniqueKey($table, $key='') {
//get the array of table indexes
$indexes = DB::connection()->getDoctrineSchemaManager()->listTableIndexes($table);
//abort if there are no indexes
if(!is_array($indexes)) return false;
//set up the default array of index keys
$keys = ['primary', 'unique'];
//if a key was passed and it is valid, use it...but cast as an array
if($key!='' && in_array($key, $keys)) $keys = (array) $key;
//loop through the keys array
foreach ( $keys as $key ) {
//keep it honest
if ( array_key_exists( $key, $indexes ) ) {
//get the columns for this key
$columns = $indexes[ $key ]->getColumns();
//if we have an array of columns, we have what we need
if ( is_array( $columns ) ) {
return $columns;
}
}
}
//if you got here, you did not get find what you were looking for
return false;
}

Answer 2

The Illuminate/Database/Eloquent/Model class has a getKeyName function which is public.
Inside your model class, you can access the primary key using $this->getKeyName().

Answer 3

my approach is :
$result = DB::select(DB::raw("SHOW KEYS FROM {$table} WHERE Key_name = 'PRIMARY'"));
$primaryKey = $result[0]->Column_name;
and i use mysql

Answer 4

You can use ->getKey() on a model:
$someModel->getKey();
Or if you're just trying to get the name of the column, without having an instance of the model:
app(App\Model::class)->getKeyName()

Answer 5

$primary_key = app($builder->getModel())->getKeyName();
if you referenced the model when you initialized that Query Builder instance you can retrieve the model reference then use it to get the keyName. but if your just directly called a new Query Builder there isn't a way to see the primary key without doing a select against the table keys, maybe in a subselect?
SHOW KEYS FROM table WHERE Key_name = 'PRIMARY'