Using this query to get the products with words that fulfill all three required word terms (lenovo, laptop, computer):
SELECT t1.id, t1.name, t1.price FROM
(SELECT p.id AS productid, name, price
FROM products p JOIN productwords pw ON p.id = pw.productid
JOIN words w ON pw.wordid = w.id WHERE word.term = 'lenovo') t1
INNER JOIN
(SELECT p.id AS productid, name, price
FROM products p JOIN productwords pw ON p.id = pw.productid
JOIN words w ON pw.wordid = w.id WHERE word.term = 'laptop') t2
INNER JOIN
(SELECT p.id AS productid, name, price
FROM products p JOIN productwords pw ON p.id = pw.productid
JOIN words w ON pw.wordid = w.id WHERE word.term = 'computer') t3
ON
t1.productid = t2.productid
AND
t1.productid = t3.productid
ORDER BY t1.name
As far as I can see, the query considers the whole words table for each term (the tables have indexes. Database is MySql).
Can the query be rewritten in a better way, so it will become faster? (the tables contain millions of rows)
For example with subsets, so the 'laptop' search only considers the rows matching 'lenovo' - and the 'computer' search only considers the rows matching first 'lenovo' and then 'laptop'.
Thanks!
You can use the HAVING clause :
SELECT p.id AS productid, name, price
FROM products p
JOIN productwords pw ON p.id = pw.productid
JOIN words w ON pw.wordid = w.id
WHERE word.term in ('lenovo','computer','laptop')
GROUP BY p.id , name, price
HAVING COUNT(DISTINCT word.term) = 3
That is if I understood the question, it looks like product -> words is 1:n relation , and if no column from the word table is selected, that should work perfectly.
This might be a quicker way of doing it:
SELECT p.id, name, price
FROM products p
where
EXISTS (select null
from productwords pw1
JOIN words w1 ON pw1.wordid = w1.id
where w1.term = 'lenovo'
and p.id = pw1.productid )
and EXISTS (select null
productwords pw2
JOIN words w2 ON pw2.wordid = w2.id
where w2.term = 'laptop'
and and p.id = pw2.productid )
and EXISTS (select null
productwords pw3 ON p.id = pw3.productid
JOIN words w3
where w3.term = 'computer'
and p.id = pw3.productid )
ORDER BY name;
Related
I'm converting my database from MySQL to PostgresSQL, and I have this query which tries to sord the products by the cheapest price and the most popular in a given location. It works fine in MySQL, but in Postgres I'm running into problems with this query :
SELECT products.product_id,
suppliers.supplier_id,
product_code.desc_fa,
products.name_fa,
MIN(product_supplier.price) AS price,
SUM(COALESCE(orders.quantity, 0)) AS n_orders
FROM products
JOIN product_code ON product_code.code_id = products.code_id
JOIN product_supplier ON product_supplier.product_id = products.product_id
JOIN suppliers ON suppliers.supplier_id = product_supplier.supplier_id
JOIN product_tags ON product_tags.product_id = products.product_id
JOIN tags ON tags.tag_id = product_tags.tag_id
JOIN product_crop ON product_crop.product_id = products.product_id
JOIN crops ON crops.crops_id = product_crop.crop_id
LEFT JOIN orders
ON orders.product_id = products.product_id and orders.crop_id = product_crop.crop_id
LEFT JOIN user ON user.user_id = orders.user_id and user.location_id = 883
WHERE crops.crops_id = 1
AND product_supplier.quantity >= 3
AND tags.tag = 'علف کش'
GROUP BY products.name_fa
ORDER BY n_orders DESC
LIMIT 10;
It gives me this error :
column must appear in the GROUP BY clause or be used in an aggregate function
Any suggestions to how to work around this error ?
UPDATE :
According to the answers i was able to make it work by using this query:
WITH tem_1 AS (SELECT product_id, MIN(price) AS price FROM product_supplier GROUP BY product_id) ,
tem_2 AS (SELECT product_id, SUM(quantity) AS n_orders FROM orders Group by product_id)
SELECT products.product_id, suppliers.supplier_id, product_code.desc_fa, products.name_fa, tem_1.price,
products.telegraph, suppliers.location_id, COALESCE(tem_2.n_orders,0) AS quant FROM products
INNER JOIN product_supplier ON product_supplier.product_id = products.product_id
INNER JOIN suppliers ON suppliers.supplier_id = product_supplier.supplier_id
INNER JOIN product_code ON product_code.code_id = products.code_id
INNER JOIN product_crop ON product_crop.product_id = products.product_id
INNER JOIN crops ON crops.crops_id = product_crop.crop_id
INNER JOIN product_tags ON product_tags.product_id = products.product_id
INNER JOIN tags ON tags.tag_id = product_tags.tag_id
INNER JOIN tem_1 ON tem_1.price = product_supplier.price AND tem_1.product_id = products.product_id
LEFT JOIN tem_2 ON tem_2.product_id = products.product_id
WHERE crops.crops_id = 1 AND product_supplier.quantity >= 3 AND tags.tag = 'علف کش'
ORDER BY quant DESC
LIMIT 10;;
But since i'm fairly new to SQL, I wanted to know if my code is correct or is there a better way to implement it?
When you use aggregate function (as SUM, MIN and others) the other columns in your field list without aggregate function must be included in GROUP BY clause.
These fields:
products.product_id,
suppliers.supplier_id,
product_code.desc_fa,
products.name_fa
must be in GROUP BY.
Instead your GROUP BY clause has only the following field:
products.name_fa
You must add the other missing 3 fields
In MySql this error has turned off by default, so your query works fine, but in other DBMS you are in an error case.
You can see here how set MySql environment about the GROUP BY behaviour
I want to show maximum of guarantee which specific user has. For example user has bought 3 items which have 1,2,5 years guarantee. So I want to show 5 years guarantee and name of this product.
I did subquery in case few products have this same guarantee.
SELECT t.`id-user`, name, guarantee FROM transactions t
JOIN user u ON `t`.`id-user` = `u`.`id-user`
JOIN products p ON `p`.`id-product = `t`.`id-product`
WHERE guarantee = (SELECT MAX(p2.guarantee)
FROM products p2
WHERE `p2`.`id-product` = `p`.`id-product`)
This query shows all products and their guarantees.
I think the simplest method is the substring_index()/group_concat() method for getting values associated with a maximum/minimum:
SELECT t.iduser, u.name,
MAX(p.guarantee) as guarantee,
SUBSTRING_INDEX(GROUP_CONCAT(p.name ORDER BY p.guarantee DESC), ',', 1)
FROM transactions t JOIN
user u
ON t.iduser = u.iduser JOIN
products p
ON p.idproduct = t.idproduct
GROUP BY t.iduser, u.name;
You can use your method too, but the correlated subquery is tricky:
SELECT t.iduser, u.name, p.guarantee, p.name
FROM transactions t JOIN
user u
ON t.iduser = u.iduser JOIN
products p
ON p.idproduct = t.idproduct
WHERE p.guarantee = (SELECT MAX(p2.guarantee)
FROM transactions t2 JOIN
products p2
ON p2.idproduct = t2.idproduct
WHERE t2.iduser = u.iduser
);
I think it work.
select [User].Name as [UserName],
Product.MaxGuarantee,
Product.Name as Product_Name
from [Users] [User]
left join Transactions [Transaction]
on [Transaction].[User] = [User].ID
cross apply(
select max(guarantee) MaxGuarantee, Name
from Products
where ID = [Transaction].Product
) Product
where [User].ID = ''
I have this query and I am getting error #1066 - Not unique table/alias: 'components'. What seems to be the issue?
SELECT COUNT(*) FROM `products`, `components`, `tradeNames`
INNER JOIN `componentsMap` ON componentsMap.product_id = product.id
INNER JOIN `components` ON componentsMap.component_id = components.id
INNER JOIN `tradeNamesMap` ON .tradeNamesMap.product_id = products.id
INNER JOIN `tradeNames` ON tradeNamesMap.tradeName_id = tradeNames.id
WHERE (((((LOWER(inci) LIKE '%abies%')
OR (trade_name.LOWER(name) LIKE '%abies%'))
OR (components.LOWER(no_cas)='abies'))
OR (components.LOWER(no_einecs)='abies'))
OR (components.LOWER(name)='abies'))
AND (`published`=1)
ORDER BY `trade_name`.`name` DESC
You don't need to list the tables before the INNER JOINs. In fact, simply don't ever use commas in the FROM clause. So:
SELECT COUNT(*)
FROM `products`
INNER JOIN `componentsMap` ON componentsMap.product_id = product.id
INNER JOIN `components` ON componentsMap.component_id = components.id
INNER JOIN `tradeNamesMap` ON tradeNamesMap.product_id = products.id
INNER JOIN `tradeNames` ON tradeNamesMap.tradeName_id = tradeNames.id
WHERE (((((LOWER(inci) LIKE '%abies%')
OR (trade_name.LOWER(name) LIKE '%abies%'))
OR (components.LOWER(no_cas)='abies'))
OR (components.LOWER(no_einecs)='abies'))
OR (components.LOWER(name)='abies'))
AND (`published`=1)
ORDER BY `trade_name`.`name` DESC;
The above query only returns one row because of the COUNT(). The order by suggests that you actually want this information for each trade_name.name. If so, you need a GROUP BY:
SELECT tn.name, COUNT(*)
FROM `products` p INNER JOIN
`componentsMap cm
ON cm.product_id = p.id INNER JOIN
`components` c
ON cm.component_id = c.id INNER JOIN
`tradeNamesMap` tnm
ON tnm.product_id = p.id INNER JOIN
`tradeNames` tn
ON tnm.tradeName_id = tn.id
WHERE ((LOWER(inci) LIKE '%abies%') OR
(tn.LOWER(name) LIKE '%abies%') OR
(c.LOWER(no_cas)='abies') OR
(c.LOWER(no_einecs)='abies') OR
(c.LOWER(name)='abies')
) AND
(`published` = 1)
GROUP BY tn.name
ORDER BY tn.`name` DESC
INNER JOIN `[components]` ON componentsMap.component_id = components.id
AND
SELECT COUNT(*) FROM `products`, [`components`], `tradeNames`
Two components are there.
Just guessing, and untested, but I suspect that something like this would do what you're after...
SELECT n.name
, COUNT(*)
FROM products p
JOIN componentsMap pc
ON pc.product_id = p.id
JOIN components c
ON c.id = pc.component_id
JOIN tradeNamesMap pn
ON pn.product_id = p.id
JOIN tradeNames n
ON n.id = pn.tradeName_id
WHERE
( inci LIKE '%abies%'
OR n.name LIKE '%abies%'
OR 'abies' IN (c.no_cas,c.no_einecs,c.name)
)
AND published = 1
GROUP
BY n.name
ORDER
BY n.name DESC
I don't know much about query optimization but I know the order in which queries get executed
FROM clause
WHERE clause
GROUP BY clause
HAVING clause
SELECT clause
ORDER BY clause
This the query I had written
SELECT
`main_table`.forum_id,
my_topics.topic_id,
(
SELECT MAX(my_posts.post_id) FROM my_posts WHERE my_topics.topic_id = my_posts.topic_id
) AS `maxpostid`,
(
SELECT my_posts.admin_user_id FROM my_posts WHERE my_topics.topic_id = my_posts.topic_id ORDER BY my_posts.post_id DESC LIMIT 1
) AS `admin_user_id`,
(
SELECT my_posts.user_id FROM my_posts WHERE my_topics.topic_id = my_posts.topic_id ORDER BY my_posts.post_id DESC LIMIT 1
) AS `user_id`,
(
SELECT COUNT(my_topics.topic_id) FROM my_topics WHERE my_topics.forum_id = main_table.forum_id ORDER BY my_topics.forum_id DESC LIMIT 1
) AS `topicscount`,
(
SELECT COUNT(my_posts.post_id) FROM my_posts WHERE my_topics.topic_id = my_posts.topic_id ORDER BY my_topics.topic_id DESC LIMIT 1
) AS `postcount`,
(
SELECT CONCAT(admin_user.firstname,' ',admin_user.lastname) FROM admin_user INNER JOIN my_posts ON my_posts.admin_user_id = admin_user.user_id WHERE my_posts.post_id = maxpostid ORDER BY my_posts.post_id DESC LIMIT 1
) AS `adminname`,
(
SELECT forum_user.nick_name FROM forum_user INNER JOIN my_posts ON my_posts.user_id = forum_user.user_id WHERE my_posts.post_id = maxpostid ORDER BY my_posts.post_id DESC LIMIT 1
) AS `nickname`,
(
SELECT CONCAT(ce1.value,' ',ce2.value) AS fullname FROM my_posts INNER JOIN customer_entity_varchar AS ce1 ON ce1.entity_id = my_posts.user_id INNER JOIN customer_entity_varchar AS ce2 ON ce2.entity_id=my_posts.user_id WHERE (ce1.attribute_id = 1) AND (ce2.attribute_id = 2) AND my_posts.post_id = maxpostid ORDER BY my_posts.post_id DESC LIMIT 1
) AS `fullname`
FROM `my_forums` AS `main_table`
LEFT JOIN `my_topics` ON main_table.forum_id = my_topics.forum_id
WHERE (forum_status = '1')
And now I want to know if there is any way to optimize it ? Because all the logic is written in Select section not From, but I don't know how to write the same logic in From section of the query ?
Does it make any difference or both are same ?
Thanks
Correlated subqueries should really be a last resort, they often end up being executed RBAR, and given that a number of your subqueries are very similar, trying to get the same result using joins is going to result in a lot less table scans.
The first thing I note is that all of your subqueries include the table my_posts, and most contain ORDER BY my_posts.post_id DESC LIMIT 1, those that don't have a count with no group by so the order and limit are redundant anyway, so my first step would be to join to my_posts:
SELECT *
FROM my_forums AS f
LEFT JOIN my_topics AS t
ON f.forum_id = t.forum_id
LEFT JOIN
( SELECT topic_id, MAX(post_id) AS post_id
FROM my_posts
GROUP BY topic_id
) AS Maxp
ON Maxp.topic_id = t.topic_id
LEFT JOIN my_posts AS p
ON p.post_id = Maxp.post_id
WHERE forum_status = '1';
Here the subquery just ensures you get the latest post per topic_id. I have shortened your table aliases here for my convenience, I am not sure why you would use a table alias that is longer than the actual table name?
Now you have the bulk of your query you can start adding in your columns, in order to get the post count, I have added a count to the subquery Maxp, I have also had to add a few more joins to get some of the detail out, such as names:
SELECT f.forum_id,
t.topic_id,
p.post_id AS `maxpostid`,
p.admin_user_id,
p.user_id,
t2.topicscount,
maxp.postcount,
CONCAT(au.firstname,' ',au.lastname) AS adminname,
fu.nick_name AS nickname
CONCAT(ce1.value,' ',ce2.value) AS fullname
FROM my_forums AS f
LEFT JOIN my_topics AS t
ON f.forum_id = t.forum_id
LEFT JOIN
( SELECT topic_id,
MAX(post_id) AS post_id,
COUNT(*) AS postcount
FROM my_posts
GROUP BY topic_id
) AS Maxp
ON Maxp.topic_id = t.topic_id
LEFT JOIN my_posts AS p
ON p.post_id = Maxp.post_id
LEFT JOIN admin_user AS au
ON au.admin_user_id = p.admin_user_id
LEFT JOIN forum_user AS fu
ON fu.user_id = p.user_id
LEFT JOIN customer_entity_varchar AS ce1
ON ce1.entity_id = p.user_id
AND ce1.attribute_id = 1
LEFT JOIN customer_entity_varchar AS ce2
ON ce2.entity_id = p.user_id
AND ce2.attribute_id = 2
LEFT JOIN
( SELECT forum_id, COUNT(*) AS topicscount
FROM my_topics
GROUP BY forum_id
) AS t2
ON t2.forum_id = f.forum_id
WHERE forum_status = '1';
I am not familiar with your schema so the above may need some tweaking, but the principal remains - use JOINs over sub-selects.
The next stage of optimisation I would do is to get rid of your customer_entity_varchar table, or at least stop using it to store things as basic as first name and last name. The Entity-Attribute-Value model is an SQL antipattern, if you added two columns, FirstName and LastName to your forum_user table you would immediately lose two joins from your query. I won't get too involved in the EAV vs Relational debate as this has been extensively discussed a number of times, and I have nothing more to add.
The final stage would be to add appropriate indexes, you are in the best decision to decide what is appropriate, I'd suggest you probably want indexes on at least the foreign keys in each table, possibly more.
EDIT
To get one row per forum_id you would need to use the following:
SELECT f.forum_id,
t.topic_id,
p.post_id AS `maxpostid`,
p.admin_user_id,
p.user_id,
MaxT.topicscount,
maxp.postcount,
CONCAT(au.firstname,' ',au.lastname) AS adminname,
fu.nick_name AS nickname
CONCAT(ce1.value,' ',ce2.value) AS fullname
FROM my_forums AS f
LEFT JOIN
( SELECT t.forum_id,
COUNT(DISTINCT t.topic_id) AS topicscount,
COUNT(*) AS postCount,
MAX(t.topic_ID) AS topic_id
FROM my_topics AS t
INNER JOIN my_posts AS p
ON p.topic_id = p.topic_id
GROUP BY t.forum_id
) AS MaxT
ON MaxT.forum_id = f.forum_id
LEFT JOIN my_topics AS t
ON t.topic_ID = Maxt.topic_ID
LEFT JOIN
( SELECT topic_id, MAX(post_id) AS post_id
FROM my_posts
GROUP BY topic_id
) AS Maxp
ON Maxp.topic_id = t.topic_id
LEFT JOIN my_posts AS p
ON p.post_id = Maxp.post_id
LEFT JOIN admin_user AS au
ON au.admin_user_id = p.admin_user_id
LEFT JOIN forum_user AS fu
ON fu.user_id = p.user_id
LEFT JOIN customer_entity_varchar AS ce1
ON ce1.entity_id = p.user_id
AND ce1.attribute_id = 1
LEFT JOIN customer_entity_varchar AS ce2
ON ce2.entity_id = p.user_id
AND ce2.attribute_id = 2
WHERE forum_status = '1';
I have following query.
select
Product.*,
(
select
group_concat(features.feature_image order by product_features.feature_order)
from product_features
inner join features
on features.id = product_features.feature_id
where
product_features.product_id = Product.id
and product_features.feature_id in(1)
) feature_image
from products as Product
where
Product.main_product_id=1
and Product.product_category_id='1'
I want to bypass the row if feature_image is empty.
Your query looks a bit strange because you are doing most of the work in a subquery:
select p.*, (select group_concat(f.feature_image order by pf.feature_order)
from product_features pf inner join
features f
on f.id = pf.feature_id
where pf.product_id = p.id and pf.feature_id in (1)
) as feature_image
from products p
where p.main_product_id=1 and p.product_category_id='1';
A more common way to phrase the query is as an inner join in the outer query:
select p.*, group_concat(f.feature_image order by pf.feature_order) as feature_image
from products p join
product_features pf
on pf.product_id = p.id and pf.feature_id in (1) join
features f
on f.id = pf.feature_id
where p.main_product_id=1 and p.product_category_id='1'
group by p.id;
This will automatically include only products that have matching features. You would use left outer join to get all products.