php - Dynamically change table data based on the order of another table mysql -

php - Dynamically change table data based on the order of another table mysql -

new mysql , need help big time! have 2 tables - table , table b set this:

table - event.

event | date | time ===== 1 | 2014-07-06 | 9am 2 | 2014-08-08 | 10am 3 | 2014-10-10 | 10am

table b - location

event | date | description | directions* ===== 1 | 2014-08-08 | grand canyon | bar 2 | 2014-10-06 | devils tower | foo 3 | 2014-07-06 | pacific park | foo 3 | 2014-07-06 | universal studios | foo

now problem i'm having how re-order or swap values in table b - locations. according table -event. how update locations table alter well?

basically need find previous event values , update them new event values.

this outcome of table b - location see when table a-event changed.

table b - location

event | date | description | directions ===== 1 | 2014-07-06 | pacific park | foo 1 | 2014-07-06 | universal studios | foo 2 | 2014-08-08 | grand canyon | bar 3 | 2014-10-06 | devils tower | foo

i forgot mention need able loop through , find instances. well

if using innodb storage engine, can specify on update cascade rule on foreign key constraint definition:

alter table `location` add together constraint fk_location_event (event) references event (event) on update cascade;

then (as long foreign_key_checks not disabled in session), when issue update statement alter value of the event column in event table, related rows in location table modified.

for example, if issue statement:

update `event` set `event` = 4 `event` = 1;

it equivalent performing these 2 statements:

update `event` set `event` = 4 `event` = 1; update `location` set `event` = 4 `event` = 1;

php mysql