Can I do this in one query or do I have to do the checking in another language?

Well this seems to work… Correct me if im wrong

What do you want to join if you are selecting count?

Genreid

To count of tracks?

Yes, tracks with a given genre

You dont need join, you have genreid

There is genreid and music name in one table

There is genreid and genre name in other table

Try to make a reversed selection

I want to count the number of songs with genre name …

From genre to track

I have no idea about this 😐

And also read about joins. You have incorrect one

Is there a need to joinM

I told what do you need to do

Read about joins and check out some examples

It’s very simple query.
Read Martin Gruber’s book for this.

Here even a join is not strictly necessary, though, you can do this with a join

no this is incorrect.

Yeah, i forgot the join condition

He must select the genre by its name, first.

Now it is working fine

+

The schema is this

How to connect these tables

read books, don’t study by ‘try and fail’ method.

I will santa

I’m not Santa

It’s umpaloomp

You need an Order Dimension between these two dimensions to do anything meaningful with these two many to many relationship dimensions.

Employee – > Order <- Customer

Yes. Partitioning is useful in dealing with rotating data. If MySQL can easily identify rows to delete and map them to single partition, instead of running DELETE FROM table WHERE. One can truncate the partition if Range partitioned.

Decide what the model would be used for then Design on paper, redo if required, then touch mysql

Hi. I have a MySQL question. I have two tables, A and B. A’s primary key is a foreign key in B. How would I go about setting the value of A.description as the default for B.description?

Table field’s defaults must be only simple constant values or simple expressions based on constants and functions, you cannot reference other tables in a DEFAULT constraint .

For this, you have to use triggers.

But I would not do this at all, you can just substitute value of B.description with value of A.description if B.description is empty, in all selecting queries.

Thank you, I did not think of this. I did not want to populate the field with triggers because I would also have to handle updates to A.description.

This implies that, in my queries, I should check if B.description is empty, and if so, fetch A.description in its place. Correct?

Follow up question, if so. Can I do this in one query or do I have to do the checking in another language?

Yes. this can be done with simple CASE expression or COALESCE() function.

This can and (I think) must be done in a simple query

Pardon my ignorance, but how would such a query look?

Something like this?

SELECT …
COALESCE( B.description, A.description ) as description
from A join B on …

this is not correct, must be B left join A, but B seems to be dependent , child entity, can’t exist without A, so this is INNER JOIN

Hi All
We are getting access denied for user on log(mysql-critter.err) in mysql database.

What could be the issue?
Where to check the issue and how to resolve the issue?

users in MySQL depend also on the host, from which you connect to the DB. So if you use a login Mrfoo and you connect from one host , this is one user, and if you use same login, but connect from another host — this is another user.

So check this first of all

Can someone recommend me books which will cover from basics to advanced in SQL?

Martin Gruber

Free understanding MySQL?