[Koha-bugs] [Bug 27534] koha upgrade throws SQL error while applying Bug 25333 - Change message transport type for Talking Tech from "phone" to "itiva"

[bugzilla-daemon at bugs.koha-community.org]

https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=27534

--- Comment #13 from Manos PETRIDIS <egpetridis at yahoo.com> ---
I believe they may:

 ALTER TABLE letter DROP CONSTRAINT message_transport_type_fk 
 ALTER TABLE letter ADD CONSTRAINT message_transport_type_fk 
   FOREIGN KEY (message_transport_type) 
   REFERENCES message_transport_types(message_transport_type)    
   ON DELETE CASCADE ON UPDATE CASCADE

Generally speaking, a foreign key can be used for improved preformance (hint
for implicit joins) even if no rules (constraints) are defined for data
referential integrity. Foreign keys may well be defined without corresponding
constraints, as it was apparently the case in older koha DBs. Constraints
howerver need to be supported by indexes and foreign key definitions in order
to enforce data integrity rules in time. 

In any case, all's well that ends well :-)

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