I am using CodeIgniter 4. First I write this to get records from the database, but this shows me an error ( Call to a member function table() on null)
$CI = & get_instance();
$CI -> db -> select('*');
$CI -> db -> from($table_name);
Then I read from documentation and write this
$db->table("tablename");
But this method also failed.
The Query Builder is loaded through the table() method on the database connection. This sets the FROM portion of the query for you and returns a new instance of the Query Builder class:
$db = \Config\Database::connect();
$builder = $db->table('users');
//loading query builder
$output = $builder->table('table_name')
->get();
// Produces: SELECT * FROM table_name
To get result as array you can add one more line of code.
$output = $output->getResultArray();
For selecting particular fileds.
$db = \Config\Database::connect();
$builder = $db->table('users');
//loading query builder
$output = $builder->table('table_name')
->select('filedname2, fieldname2, fieldname3,..')
->get();
$output = $output->getResultArray();
You can use where clause also for more details refer to codeigniter4 documentation page. https://codeigniter4.github.io/userguide/database/query_builder.html#looking-for-specific-data
//initialize database connection
$db = \Config\Database::connect();
//created builder to get queries results
$builder = $db->table('users');
//select particular columns
$builder->select('id','first_name','last_name');
//if you want to select all columns
$builder->select('*')
//if you want to put where
$builder->where('id',1);
//if you want to put order by desc or asc
$builder->orderBy('id desc');
//get records
$output = $builder->get();
//if you want to return your results in array format then,
return $output->getResultArray();
//if you want to return your results in std object then,
return $output->getResult();