Joins without foreign key

Joins without foreign key

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Joins without foreign key
Tag : mysql , By : kbrust
Date : January 12 2021, 08:33 AM

Hope this helps Yes and no depending on how data gets in to those tables.
Yes, if records in the second table will always be created after the first (ie the second tables data is some information that will come later)

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Foreign Keys vs Joins

Tag : sql , By : jaime
Date : March 29 2020, 07:55 AM
this one helps. Foreign keys are just constraints to enforce referential integrity. You will still need to use JOINs to build your queries.
Foreign keys guarantee that a row in a table order_details with a field order_id referencing an orders table will never have an order_id value that doesn't exist in the orders table. Foreign keys aren't required to have a working relational database (in fact MySQL's default storage engine doesn't support FKs), but they are definitely essential to avoid broken relationships and orphan rows (ie. referential integrity).

Rails where joins for different foreign key

Tag : ruby-on-rails , By : Stephen Judge
Date : March 29 2020, 07:55 AM
help you fix your problem The employees table isn't being aliased as super, and doesn't need to be aliased at all in this case since it's only joined one time:
workorders = workorders.joins(:client,:super).
               where("wonum like :search or description like :search or clients.client_name like :search or employees.employee_full_name like :search ", 
               search: "%#{params[:sSearch]}%")
scope :search, lambda{ |term|
  %w(wonum description clients.client_name employees.employee_full_name).
    map{|field| "#{field} like :search" }.
    join(" or "), search: term

workorders = workorders.joins(:client, :super).search("%#{params[:sSearch]}%")

SQL. Re: inner joins & foreign keys

Tag : asp.net , By : jch
Date : March 29 2020, 07:55 AM
hop of those help? First, inner join is how you get your tables "back together", and @SpectralGhost's example is how you do it. But you might want to consider doing it in the database rather than in your ASP code. The way you do that is with views. If you create a view (the syntax is CREATE VIEW and there are plenty of examples out there) then you can make the database schema as complex as you need to without making it hard to use in your ASP application. You can even make views updatable (you define an "INSTEAD OF" trigger, again, many examples if you search).
But you probably don't want to update a view, or a table, directly from your ASP code. You probably want to define STORED PROCEDUREs that update your data, and call those from your ASP code. This allows you to restrict access to your tables and views to read only and force any writes to come through a stored procedure you can control better. This prevents SQL INJECTION, making your ASP application much more secure. If the service account the application pool you ASP page runs under can pass raw queries to the database then any compromise can do tremendous damage to your database. If all it can do is execute a stored procedure where the parameters can be changed but not the functionality, they can only put some junk values in, or maybe not even that if you range check well.

Foreign Key Types on Joins

Tag : sql-server , By : Adam May
Date : March 29 2020, 07:55 AM
I wish did fix the issue. The main factor in the performance of an equality comparison (that does not involve type casting or converting) is the size of the datatype. The integer types in SQL Server have fixed sizes (4 bytes for an int, 8 bytes for a bigint, etc. - refer to the documentation for the full details), so the actual data is inconsequential. Varchars, on the other hand (and as opposed to chars), vary in their size depending on the size of the data (see the docs for details), so having shorter data may indeed affect a query's performance, but you'll have to have a pretty large number of rows to notice any difference.

Joins using foreign key codeigniter

Tag : codeigniter , By : user185751
Date : March 29 2020, 07:55 AM
like below fixes the issue The simplest query to get the data you want it using a join. Instead of using Query Builder I will use db->query()
public function absence(){
    $id2= $this->session->CNE;
    $query = $this->db->query("Select * From absence_etudiant Inner Join absence On absence.id_absence = absence_etudiant.CNE Where absence_etudiant.CNE = $id2");

    $data['absences'] = $query->result();
    $this->load->view('Etudiants/affi', $data);
    <?php foreach($absences as $absence) : ?>
        <td><strong><?php echo $absence->id_absence; ?></strong></td>
        <td><?php echo $absence->id_seance; ?></td>
        <td><?php echo $absence->justification; ?></td>
        <td><?php echo $absence->course; ?></td>
    <?php endforeach; ?>
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