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Simply put, how can I do this query using Sequel?
select a.id, count(t.id)
from albums a
right join tracks t on t.album_id = a.id
group by a.id
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SQL – count() with Group By clause The count() function is an aggregate function use to find the count of the rows that satisfy the fixed conditions. The count() function with the GROUP BY clause is used to count the data which were grouped on a particular attribute of the table.
The use of COUNT() function in conjunction with GROUP BY is useful for characterizing our data under various groupings. A combination of same values (on a column) will be treated as an individual group.
To count the number of rows, use the id column which stores unique values (in our example we use COUNT(id) ). Next, use the GROUP BY clause to group records according to columns (the GROUP BY category above). After using GROUP BY to filter records with aggregate functions like COUNT, use the HAVING clause.
In SQL, you can make a database query and use the COUNT function to get the number of rows for a particular group in the table. Here is the basic syntax: SELECT COUNT(column_name) FROM table_name; COUNT(column_name) will not include NULL values as part of the count.
DB[:albums___a].
right_join(:tracks___t, :album_id=>:id).
select_group(:a__id).
select_more{count(:t__id)}
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