Tagged Questions
0
votes
1answer
17 views
HOW to “SUM” and “JOIN” for single query of a poll results?
I have a poll database as
CREATE TABLE poll_answer
answer_id,
answer varchar(255),
poll_id int(11),
FOREIGN KEY(poll_id) REFERENCES polls(poll_id) ON DELETE CASCADE,
PRIMARY KEY(answer_id)
) ...
2
votes
1answer
379 views
MySQL 5.5.8 InnoDB Foreign Key, JOIN performance
We are using aws/rds, MySQL 5.5.8. all InnoDB.
For performance purposes, we have merged some data-elements into varchar fields; mini-sized int and date type fields; added covering indexes; ...
1
vote
1answer
228 views
Usefulness of Foreign Key WITHOUT reference option
Sorry, if this is naive question, but I searched a lot and did not get a vivid answers. Consider a simple InnoDB FOREIGN KEY without ON DELETE or ON UPDATE
I think this will avoid INSERT of a value ...
9
votes
3answers
178 views
Are there any database engines which will intuit the join condition based on the existing foreign keys?
It seems strange to me that, when I've defined a foreign key, the engine cannot use this information to automatically figure out the correct JOIN expressions, but instead requires me to re-type the ...
5
votes
3answers
229 views
What does the output of a JOIN statement look like?
I've been wanting to use joins for a while, but I'm having trouble visualizing the output so I know how to put it to use.
Let's say I have 2 tables:
CREATE TABLE Cities (
id INT UNSIGNED PRIMARY ...
