I have a mySQL statement with two joins like this:
SELECT a.userID, sum(b.score) as totalScore, c.userName FROM b
Inner Join a on b.noteID = a.noteID
Inner Join user on c.userID = a.userID
Where totalScore != 0
group by a.userID order by totalScore desc
But when I run the query it can not decipher the sum that I labeled with the as
LIMIT 0, 1000 Error Code: 1054. Unknown column 'totalScore' in 'where clause' 0.18
Use a having clause instead
select a.userID, c.userName,
sum(b.score) as totalScore
FROM b
Inner Join a on b.noteID = a.noteID
Inner Join user on c.userID = a.userID
group by a.userID, c.userName
having totalScore != 0
order by totalScore desc
You can't use alias names from the select in the where clause
totalScore is a value that refers to the whole group and not just a single record, so you have to put it in the having
You should not select c.userName since it is neither aggregated nor in the group by clause. In strict mode MySQL throws an error and other DB engines will always throw an error
Related
I have this query that will LEFT JOIN and GROUP BY to get SUM of column.
SELECT
c.id,
SUM(
r.score
) AS score_sum,
SUM(
CASE WHEN r.is_active = '0' THEN r.negative ELSE 0 END
) AS negative_sum
FROM comments AS c
LEFT JOIN rates AS r ON (r.comment_id = c.id)
WHERE r.comment_id = c.id
GROUP BY c.id
DB Fiddle link:
https://dbfiddle.uk/?rdbms=mysql_5.7&fiddle=fadba795d8426f91471fa4db83845b6f
The query works, but if the comments records is large (10K for example), I need to implement pagination, how do I modify this query to limit the comments records first before GROUP BY?
In short:
Get the first 5 comments by limit to 5
Left join the table rates
Get the SUM by group by
Example, show the first 4 comments SUM
Thanks
You can use subquery to "select c.id from comments limit N" in the FROM clause.
select c.id,
sum(r.score) as score_sum,
SUM(
CASE WHEN r.is_active = '0' THEN r.negative ELSE 0 END
) AS negative_sum
from ( select c.id from comments c limit 2) c
LEFT JOIN rates AS r ON (r.comment_id = c.id)
GROUP BY c.id;
You may apply order by in the subquery to determine order in which you want to select the comments (Top N).
DB Fiddle link
Try the following:
SELECT
c.id,
SUM(
r.score
) AS score_sum,
SUM(
CASE WHEN r.is_active = '0' THEN r.negative ELSE 0 END
) AS negative_sum
FROM comments AS c
LEFT JOIN rates AS r ON (r.comment_id = c.id)
WHERE r.comment_id = c.id
GROUP BY c.id
ORDER BY c.id ASC
LIMIT 5
The rationale behind the above query is that id is the Primary key (hence indexed) in your comments table. Also, your GROUP BY and ORDER BY is on the same column, that is, id; so MySQL will first utilize the index on id and get first 5 rows (due to LIMIT), and then proceed forward to JOIN with other tables and do aggregation etc.
Give it a Try!! More details here: https://dev.mysql.com/doc/refman/5.7/en/order-by-optimization.html
We can confirm the same using EXPLAIN .. on this query.
I'm facing a little problem with mysql where clause.
This is the query:
SELECT u.id user
, p.id product_purchased
, p.name product_name
, pl.store_id store
, COUNT(*) occurrences
, total_spent
, total_product_purchased
, pl.registration
FROM purchases_log pl
JOIN user u
ON pl.user_id = u.id
JOIN product p
ON pl.product_id = p.id
JOIN
( SELECT user_id
, SUM(price) total_spent
, COUNT(product_id) total_product_purchased
FROM purchases_log pl
GROUP
BY user_id
) t1
ON u.id = t1.user_id
WHERE pl.store_id IN (1,2,3)
AND occurrences > 1
GROUP
BY user
, product_name
ORDER
BY u.id ASC
, pl.registration ASC;
This is the output error:
Error Code: 1054. Unknown column 'occurrences' in 'where clause' 0.067 sec
I have already tried assign AS to occurrences or using pl.
So, can someone explain me how to correctly define the result of a count function in where clause?
You need to use HAVING instead of COUNT as group by is applied after WHERE clause and hence, it won't know about any group/aggregate columns, e.g/:
SELECT u.id user,p.id product_purchased, p.name product_name, pl.store_id store, COUNT(*) AS occurrences, total_spent, total_product_purchased, pl.registration
FROM purchases_log pl
JOIN user u ON pl.user_id=u.id
JOIN product p ON pl.product_id=p.id
JOIN (SELECT user_id, SUM(price) AS total_spent,COUNT(product_id) AS total_product_purchased FROM purchases_log pl GROUP BY user_id) t1 ON u.id=t1.user_id
WHERE pl.store_id IN (1,2,3)
GROUP BY user, product_name
HAVING COUNT(*) > 1
ORDER BY u.id ASC, pl.registration ASC;
Update
If a user has more than one product associated then it's good to add all the non aggregate columns in GROUP BY to get all the combinations of user and product. The current query will not return all the combinations.
For further optimization, as #strawberry has suggest, you can run EXPLAIN and see which indices are used and whether there is any need to create any new index.
I get the error below:
ER_BAD_FIELD_ERROR: Unknown column 'c.id' in 'where clause':
SELECT *
FROM clients c
LEFT JOIN
(SELECT GROUP_CONCAT(smpp_user), client_id
FROM client_accounts
WHERE client_id = c.id) AS l ON
l.client_id = c.id
I need use WHERE to group smpp_user columns for each c.id from main SELECT.
Help please? I believe it's possible.
Just remove WHERE clause in your sub query and use GROUP BY:
SELECT *
FROM clients c
LEFT JOIN (
SELECT GROUP_CONCAT(smpp_user), client_id
FROM client_accounts
GROUP BY client_id
) AS l ON l.client_id = c.id
In mysql query I use order by, but it is not working.
When I do this
SELECT t.id,t.user_id,t.title,c.comment,d.has_answer,IF(c.id IS NULL, t.date_created, d.recent_date) recent_date,MIN(i.id) image_id
FROM threads t
LEFT JOIN comments c ON c.thread_id = t.id
INNER JOIN (
SELECT thread_id, MAX(date_sent) recent_date, MAX(is_answer) has_answer
FROM comments
GROUP BY thread_id
) d ON c.id IS NULL OR (d.thread_id = c.thread_id AND d.recent_date = c.date_sent)
LEFT JOIN thread_images i ON t.id = i.thread_id
WHERE t.user_id = t.user_id
GROUP BY t.id
ORDER BY d.recent_date DESC
LIMIT 0, 10
It doesn't properly order them. But if I do this:
SELECT *
FROM (
SELECT t.id,t.user_id,t.title,c.comment,d.has_answer,IF(c.id IS NULL, t.date_created, d.recent_date) recent_date,MIN(i.id) image_id
FROM threads t
LEFT JOIN comments c ON c.thread_id = t.id
INNER JOIN (
SELECT thread_id, MAX(date_sent) recent_date, MAX(is_answer) has_answer
FROM comments
GROUP BY thread_id
) d ON c.id IS NULL OR (d.thread_id = c.thread_id AND d.recent_date = c.date_sent)
LEFT JOIN thread_images i ON t.id = i.thread_id
WHERE t.user_id = t.user_id
GROUP BY t.id
LIMIT 0, 10) qwerty
ORDER BY recent_date DESC
Then it does work. Why does the top one not work, and is the second way the best way to fix that?
Thanks
Those two statements are ordering by two different things.
The second statement is ordering by the result of an expression in the SELECT list.
But the first statement specifies ordering by a value of recent_date returned by the inline view d; if you remove "d." from in front of recent_date, then the ORDER BY clause would reference the alias assigned to the expression in the SELECT list, as the second statement does.
Because recent_date is an alias for an expression the SELECT list, these two are equivalent:
ORDER BY recent_date
ORDER BY IF(c.id IS NULL, t.date_created, d.recent_date)
^^
but those are significantly different from:
ORDER BY d.recent_date
^^
Note that the non-standard use of the GROUP BY clause may be masking some values of recent_date which are discarded by the query. This usage of the GROUP BY clause is a MySQL extension to the SQL Standard; most other relational databases would throw an error with this statement. It's possible to get MySQL to throw the same type of error by enabling the ONLY_FULL_GROUP_BY SQL mode.
Q Is the second statement the best way to fix that?
A If that statement guarantees that the resultset returned meets your specification, then it's a workable approach. (One downside is the overhead of the inline view query.)
But I strongly suspect that the second statement is really just masking the problem, not really fixing it.
SELECT t.id,t.user_id,t.title,c.comment,d.has_answer,IF(c.id IS NULL, t.date_created, d.recent_date) recent_date,MIN(i.id) image_id
FROM (threads t
LEFT JOIN comments c ON c.thread_id = t.id
INNER JOIN (
SELECT thread_id, MAX(date_sent) recent_date, MAX(is_answer) has_answer
FROM comments
GROUP BY thread_id
) d ON c.id IS NULL OR (d.thread_id = c.thread_id AND d.recent_date = c.date_sent)
LEFT JOIN thread_images i ON t.id = i.thread_id
WHERE t.user_id = t.user_id
GROUP BY t.id
LIMIT 0, 10) x
ORDER BY d.recent_date DESC
I have a SQL query that has a subquery that has joins. I would like to rewrite the query without the subquery so that I can create a view. MySQL does not allow SELECT statements where the FROM is a subquery.
Is this possible? I've tried removing the outer select and moving the group by inside the subs query. This partially works but some of the data is incorrect.
select *
from (SELECT r.id, r.dateAdded, r.listingId, r.rating, r.username, r.valid, tbl_data.nameShort, tbl_data.desk, d.model, d.hardware, d.serial, l.appVersion, r.photoUrl, r.comment
FROM tbl_ratings r
JOIN tbl_data on r.listingId = vi_data.id
JOIN tbl_devices d on r.serial = d.serial
JOIN tbl_log l on l.serial = d.serial
ORDER BY d.serial, l.dateAdded DESC) x
group by id
order by dateAdded DESC
Thanks in advance!
Is it as simple as:
SELECT r.id, r.dateAdded, r.listingId, r.rating, r.username, r.valid,
tbl_data.nameShort, tbl_data.desk, d.model, d.hardware,
d.serial, l.appVersion, r.photoUrl, r.comment
FROM tbl_ratings r
JOIN tbl_data on r.listingId = vi_data.id
JOIN tbl_devices d on r.serial = d.serial
JOIN tbl_log l on l.serial = d.serial
GROUP BY r.id
ORDER BY r.dateAdded DESC
Also, you have a reference to "vi_data" that isn't anywhere else in the query
Change your group by clause to be group by r.id. Since you're selecting from a derived table (the subquery), the db can't tell that there's only one "id" field in that derived table - it only sees the column headers as specified in the subquery, which is r.id.