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How to name SQL FOREIGN KEY Constraint on CREATE two tables columns into a relationship TABLE


By : user2174892
Date : October 16 2020, 08:10 PM
hop of those help? i was just wondering if there is a way to name a foreign key on create table , You can write:
code :
ADD CONSTRAINT `customized_foreign_key_name` FOREIGN KEY (`uuid`) REFERENCES `employee` (`uuid`)


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How to create foreign key constraint without relationship in Doctrine


By : Tejaram Godara
Date : March 29 2020, 07:55 AM
I wish this helpful for you You can set the foreign key on the blocked_users table when you define the relationship from blocked_user_id to user:
code :
@JoinColumn(name="blocked_user_id", referencedColumnName="id", onDelete="cascade")

Is it possible to create a foreign key relationship between two tables on String/varchar type columns in Laravel?


By : Luxferrew
Date : March 29 2020, 07:55 AM
hop of those help? Yes Surely You can do that See the Example Below:
Suppose you have your category table as below:
code :
  Schema::create('categories', function (Blueprint $table) {
        $table->increments('id');
        $table->string('slug')->unique();
        $table->timestamps();
  });
 Schema::create('subcategories', function (Blueprint $table) {
        $table->increments('id');
        $table->string('category_slug')->unique();
        $table->foreign('category_slug')
       ->references('slug')->on('categories')->onUpdate('cascade')
        ->onDelete('cascade');
        $table->timestamps();
  });

Drop a foreign key constraint between columns of two tables without knowing the foreign key name in Informix?


By : antihank
Date : March 29 2020, 07:55 AM
help you fix your problem I'm using an Informix database. I have added some foreign keys to a table without giving them a name e.g. , I tried following it worked:
code :
CREATE PROCEDURE INFORMIX.REMOVE_FK()
    DEFINE tmpvr varchar(250);
    FOREACH cur1 FOR select  b.constrname into tmpvr
            from systables a, sysconstraints b, sysindexes c, syscolumns d
            WHERE a.tabname = 'myreport' AND (d.colname='uid' or d.colname='rid')
            AND b.tabid = a.tabid AND c.idxname = b.idxname AND d.tabid = a.tabid AND (
                d.colno = c.part1 or d.colno = c.part2 or d.colno = c.part3 or d.colno = c.part4 or
                d.colno = c.part5 or d.colno = c.part6 or d.colno = c.part7 or d.colno = c.part8 or
                d.colno = c.part9 or d.colno = c.part10 or d.colno = c.part11 or d.colno = c.part12 or
                d.colno = c.part13 or d.colno = c.part14 or d.colno = c.part15 or d.colno = c.part16
            )
    EXECUTE IMMEDIATE 'ALTER TABLE myreport DROP CONSTRAINT (' || tmpvr || ')';
    END FOREACH
END PROCEDURE;
EXECUTE PROCEDURE INFORMIX.REMOVE_FK();
DROP PROCEDURE INFORMIX.REMOVE_FK();

How to add a foreign key constraint references to the IS-A-to-Two-Tables relationship?


By : srikanth elect
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further I suggest you have an extra table called account. Then saving-account and checking-account should be separate tables pointing to that.
Also, you should have an account_id field as a PK instead of account_number. As a best practice rule, PK should not have any business meaning, it should be an abstract concept.
code :
account(aid, account-number, balance, plus any other common field for account)
saving-account([optional pk], aid_ref, interest-rate, plus fields specific to saving-account)
checking-account([optional pk], aid_ref, overdraft-amount, plus fields specific to saving-account)
customer(cid, cname)
depositor(cid, aid)

Cannot create foreign key constraint on self-joining Many-to-Many relationship


By : redrouteone
Date : March 29 2020, 07:55 AM
Hope this helps The error is telling you that you cannot use DeleteBehavior.ClientSetNull (or DeleteBehavior.SetNull) because the corresponding FK property is not nullable - both ToID and FromID are of type int, hence does not allow setting to null (neither client nor server).
To turn off the cascade delete (in order to break the multiple cascade paths I guess) for required FK relationships, use DeleteBehavior.Restrict instead.
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