Basically I have a table all customer will have a default row with customer_group_id=0
But some of this customer will belong to customer_group_id=1
When that happen a new row is created for customer with customer_group_id=1 therefore now I have 2 rows for same customer but different customer_group_id.
Now when I fetch the data I need first to select * from customer table where customer_group_id =1 but if doesn't exist give me then with customer_group_id = 0 which is the default, and continue until it returns all data.
Anyone know the best way to achieve this fast?
UPDATE: screen shoot show 2 rows with same customer_id different customer_group_id:
I need to one or the other no both so hierarchy is: if customer_group_id=1 exist then return that row and ignore the ohter otherwise return default which is customer_group_id=0
My full query:
SELECT `main_table`.*, `secondTable`.* FROM `customer` AS `main_table`
LEFT JOIN `customer_group` AS `secondTable` ON main_table.customer_id = secondTable.customer_id
WHERE (secondTable.customer_group_id = '1' )
AND (`secondTable`.`is_active` = '1')
If you have only two groups, then aggregation is simple:
select customer_id, max(customer_group_id)
from t
group by customer_id;
In MySQL 8+, you can implement a more customer prioritization using row_number():
select t.*
from (select t.*,
row_number() over (partition by customer_id order by customer_group_id desc) as seqnum
from t
) t
where seqnum = 1;
What you can do is fetch all the rows for the customers with customer_group_id=1 and then use UNION ALL to fetch the rows of the customers that do not have any row with customer_group_id=1 by using NOT EXISTS:
select * from tablename
where customer_group_id=1
union all
select * from tablename t
where t.customer_group_id=0
and not exists (
select 1 from tablename
where customer_id = t.customer_id and customer_group_id=1
)
For the rows with customer_group_id = 0 verify that there are no rows with customer_group_id = 1 for the same customer_id. You can use a NOT EXISTS subquery:
SELECT c.*, g.*
FROM customer AS c
JOIN customer_group AS g ON c.customer_id = g.customer_id
WHERE NOT EXISTS (
SELECT *
FROM customer_group AS g2
WHERE g2.customer_id = c.customer_id
AND g2.customer_group_id = 1
AND g.customer_group_id = 0
)
Related
I have the table contacts which contains duplicate records:
id name is_contacted created_at
I need to delete duplicates, but keep the first record(among the duplicates for each name) where is_contacted=1.
If among the record duplicates there are no records where is_contacted=1, just keep the first one.
This is what I have so far:
DELETE c1 FROM contacts c1
INNER JOIN contacts c2
WHERE
c1.id > c2.id AND
c1.name = c2.name;
Assuming that is_contacted's data type is BOOLEAN and id is the primary key of the table and this is the column that defines the order and which row should be considered first, use ROW_NUMBER window function to rank the rows of each name:
WITH cte AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY name ORDER BY is_contacted DESC, id) rn
FROM contacts
)
DELETE t
FROM contacts t INNER JOIN cte c
ON c.id = t.id
WHERE c.rn > 1;
ORDER BY is_contacted DESC, id returns the rows with is_contacted = 1 at the top (if they exist).
For versions of MySql prior to 8.0, without support of CTEs and winow functions, use a join of the table to a query that uses aggregation to get the id of the row that you want to keep:
DELETE t
FROM contacts t
INNER JOIN (
SELECT name,
COALESCE(MIN(CASE WHEN is_contacted THEN id END), MIN(id)) id
FROM contacts
GROUP BY name
) c ON c.name = t.name AND c.id <> t.id;
Below query will filter only records what you want.
You didn't mention what is primary key in your table, so I don't know how to join this back 1:1 with your whole table.
But if you are not able to determine primary key, they you can create new table using this query, drop original one and rename it to original one.
SELECT * FROM
(
SELECT *,
ROW_NUMBER(PARTITION BY name ORDER BY CASE WHEN is_contacted = 1 THEN -999999 else is_contacted END ) AS RN_
from contacts
) c
WHERE c.RN_ = 1
I have two tables,
table one name (tbl_brands) with these columns:
and second table name (tbl_loader_attachment) with these columns:
I used this MySQL code below to sort by DESC:
SELECT tbl_loader_attachment.*, tbl_brands.* FROM tbl_loader_attachment
INNER JOIN tbl_brands ON(tbl_brands.b_id=tbl_loader_attachment.b_id)
GROUP BY tbl_loader_attachment.b_id ORDER BY tbl_loader_attachment.la_id DESC
When I execute my code select the first row appear (test1) I want to select the last row get (test4)
One approach uses a GROUP BY query:
SELECT tla1.*, tb.*
FROM tbl_brands tb
INNER JOIN tbl_loader_attachment tla1
ON tb.b_id = tla1.b_id
INNER JOIN
(
SELECT b_id, MAX(la_id) AS max_la_id
FROM tbl_loader_attachment
GROUP BY b_id
) tla2
ON tla1.b_id = tla2.b_id AND
tla1.la_id = tla2.max_la_id;
If you are using MySQL 8+ (or should a future reader of this question be using MySQL 8+), then another option here is to use ROW_NUMBER:
WITH cte AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY b_id ORDER BY la_id DESC) rn
FROM tbl_loader_attachment
)
SELECT tla.*, tb.*
FROM tbl_brands tb
INNER JOIN cte tla ON tb.b_id = tla.b_id
WHERE tla.rn = 1;
I am trying this query:
SELECT * FROM heath_check where cid = '1' and eid in('3','5','7','1','6')
My table structure:
I want distinct eid but all other data as it is. For example I have two entries with an eid of 1 my query fetched both, but I want one which is in the second column.
SELECT *
FROM heath_check AS hc
INNER JOIN (
SELECT MAX(id) AS lastId
FROM heath_check
WHERE cid = '1' and eid in('3','5','7','1','6')
GROUP BY eid) AS lastIDs
ON hc.id = lastIDs.lastId
;
You need a subquery, like the above, to find the records you want for each value. If you had wanted the first ones, you could use MIN(id) instead; if you cannot count on sequential ids, it becomes much more complex with use of potentially non-unique timestamps (if they are even available).
Create a RowNumber grouped by eid and filter the RowNumber = 1 to get the expected result.
SELECT id, eid, cid,weight, s_blood_pressure
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY eid ORDER BY id DESC) AS RowNumber
FROM heath_check
WHERE cid = '1' AND eid IN ('3','5','7','1','6')
) A
WHERE RowNumber = 1
Currently I have the below query to count the number of rows with a distinct (customer username and store id) of the purchase of a certain item. How can I also count the total(all) rows where item_id = 3 in the same query?
SELECT count(*)
FROM (
SELECT DISTINCT customer_username, store_id
FROM transactions
WHERE item_id = 3)
You might try something like this:
SELECT COUNT(*), SUM(customer_cnt) FROM (
SELECT customer_username, store_id, COUNT(*) AS customer_cnt
FROM transactions
WHERE item_id = 3
GROUP BY customer_username, store_id
) t;
Try removing DISTINCT in your query:
SELECT count(*)
FROM (
SELECT customer_username, store_id
FROM transactions
WHERE item_id = 3)
Another way is a cross join of 2 inline views:
select x.distinct_rows, y.total_rows
from (select count(distinct concat(user_name, store_id)) as distinct_rows
from transactions
where item_id = 3) x
cross join (select count(*) as total_rows
from transactions
where item_id = 3) y
Here is my data. I want to take 6 rows, but I want all HeadlineCategoryId's to be unique in my result list. If I select the top 6 I would take 2 rows from HeadlineCategoryID 20 (6,2). Do you have any suggestions about it?
SELECT a.*
FROM tableName a
INNER JOIN
(
SELECT HeadlineCategoryID, MAX(Creation) max_date
FROM TableName
GROUP BY HeadlineCategoryID
) b ON a.HeadlineCategoryID = b.HeadlineCategoryID AND
a.Creation = b.max_date
ORDER BY a.Creation DESC -- << specify here how are you going to sort
LIMIT 6 -- the records you want to get
UPDATE 1
SELECT a.*
FROM tableName a
INNER JOIN
(
SELECT HeadlineCategoryID, MAX(NewsID) max_id
FROM TableName
GROUP BY HeadlineCategoryID
) b ON a.HeadlineCategoryID = b.HeadlineCategoryID AND
a.NewsID = b.max_id
ORDER BY a.Creation DESC -- << specify here how are you going to sort
LIMIT 6 -- the records you want to get
It looks like you want the six most recent records, but unique by HeadlineCategoryId. If so, this will work:
select top 6 NewsId, Creation, HeadlineCategoryId
from (select t.*,
row_number() over (partition by HeadlineCategoryId order by Creation desc) as seqnum
from t
) t
where seqnum = 1
As a note . . . This question originally indicated that it was using SQL Server, not MySQL. The solution in MySQL is not as simple. Here is one method with not exists:
select NewsId, Creation, HeadlineCategoryId
from t
where not exists (select 1
from t t2
where t2.HeadlineCategoryId = t.HeadlineCategoryId and
t2.id < t.id)
limit 6
The not exists portion is saying "where there is no other record with a larger id for a given headline category".