I can not understand what I am doing wrong.
My array:
ps_product
id_product
active
1
1
2
1
and
ps_product_sync
id_product
status
1
0
2
1
and my SQL code
SELECT pr_product.id_product, pr_product.active
FROM pr_product, pr_product_sync
WHERE pr_product.active = pr_product_sync.status
I get a result like this:
id_product
status
2
1
2
1
2
1
...
..
24 rows
I try the same with inner but result is the same, I don't have duplicates in the arrays... I don't understand why I get one row 24 times
PS. all tables looks good before posting/saving
If you query two tables and include both in the FROM clause, you create a Cartesian product of these tables. In other words, if one table has 4 rows and the other 6 rows, the result is 24 rows.
It is better to create an INNER JOIN using the key of the first table and the foreign key of the second table.
Change your query accordingly
SELECT pr_product.id_product, pr_product.active
FROM pr_product
INNER JOIN pr_product_sync
ON pr_product.id_product = ps_product_sync.id_product
WHERE pr_product.active = pr_product_sync.status
Of course, you could also compare the Keys in the WHERE clause or eliminate duplicates using DISTINCT. IMHO the most understandable solution is an INNER JOIN.
I hope this solves your problem.
Missing the primary key join.
Add:
WHERE
pr_product.id_product=pr_product_sync.id_product
AND pr_product.active=pr_product_sync.status
Related
I am trying to create a table that has columns called user_id and top5_foods (binary column). I currently have two tables, one has all of the user_ids and the foods associated with those user_ids and one table that only contains the top5 foods according to a type of calculation to select the top5 foods.
The table that I am trying to create if to have the column of the user_id and if at least one of their favorite foods is in the top_5_food table, put the value of the top5_foods as 1 and if not, 0.
Something like the following:
user_id top5_foods
----------------------
34223 1
43225 0
34323 1
I have tried to use the CASE command but it just duplicated the user_ids and mark 1 or 0 whenever it finds a food that is in the top_5_foods table. But I don't want it to duplicate. Could you please help ?
Thank you very much
If I understand correctly, a left join and aggregation:
select uf.user_id,
(count(t.food_id) > 0) as top5_foods
from user_foods uf left join
top5_foods t
on uf.food_id = t.food_id
group by uf.user_id;
I have a query like this:
DELETE A
FROM A
LEFT JOIN B ON
A.ID=B.ID
WHERE B.Status='OK'
The records from these join might resulted in more than one rows, for example:
Table A
ID
1
2
Table B
ID Status
1 OK
1 OK
2 OK
Do I have to make sure my record only match with one row? Because in these example, ID 1 will have 2 rows.
Apologize for bad english.
In SQL Server you don't have to ensure a 1 row result per row to delete. The engine will delete all rows from the deleting table that matches your joining or where conditions, even if they are being selected for more than 1 row.
The important part is which table are your deleting, make sure not to delete the wrong one!
Lets say that that I have two simple tables with the following columns and data:
Table 1 Table 2
year month year month
2017 01 2017 01
2016 12 2016 12
The primary key is a composite key that consists of the year and the month.
So a classical left join, gives me all the data in the left table with the matching rows in the right table.
If I do a left join like this:
select
t1.year, t2.month
from
table1 t1
left join table 2 t2 on (t1.year = t2.year and t1.month = t2.month)
Why do I get only two rows?? Shouldn't I get 4 rows??
Tnx,
Tom
A classical left join will give you the number of rows in the "Left Table" (the one in from) multiplied by the number of matches in the "Right Table" (the one in LEFT JOIN in this case), plus all the rows in the LEFT Table that have no match in the first table.
Number of rows in LEFT Table = 2
Number of matches in Right Table = 1
Number of rows in LEFT Table withouth matches = 0
2 x 1 + 0 = 2
Edit: Actually the multiplication is given for each row. Would be something like
Sum (row_i x matches_i) + unmatched
Where row_i is means each row, and matches_i to the matches for the i row in the first table. The difference with this is that each row could have different number of matches (the previous formula is only adapted to your case)
This will result in
1 (row1) x 1 (matches for row 1) + 1 (row2) x 1 (matches for row 2) +
0 (unmatched rows in table 1) = result
1x1 + 1x1 + 0 = result
1 + 1 = 2 = result
If you expected 4 rows maybe you wanted to get a Cartesian Product. As the comment stated, you can use Cross Join in that case
When you join tables together, you're essentially asking the database to combine data from two different tables and display it as a single record. When you perform a left join, you are saying:
Give me all the rows from Table1, as well as any associated data from
Table2 (if it exists).
In this sense, the data from Table2 doesn't represent separate or additional records to Table1 (even though they are stored as separate records in a separate table), it represents associated data. You are linking the data between the tables, not appending rows from each table.
Imagine that Table1 stored people, and Table2 stored phone numbers.
Table1 Table2
+------+-------+--------+ +------+-------+-------------+
| Year | Month | Person | | Year | Month | Phone |
+------+-------+--------+ +------+-------+-------------+
| 2017 | 12 | Bob | | 2017 | 12 | 555-123-4567|
| 2016 | 01 | Frank | | 2016 | 01 | 555-234-5678|
+------+-------+-------+ +------+-------+--------------+
You could join them together to get a list of people and their corresponding phone numbers. But you wouldn't expect to get a combination of rows from each table (two rows of people and two rows of phone numbers).
You will get two rows as both the columns have 2 rows that match exactly the sam and its a composite key.
It will make the same way if you had 4 rows in each you will only get 4 rows in total.
The Left Join takes Table1 (t1) as the Left table.
It searches for and retrieves all values from the Right ie:- from Table 2 (t2) matching the criteria T1.Year&Month = T2.Year&Month (alias GOD/s) as well as the additional join condition T1.Month=T2.Month. The result is that only 2 rows from T1 match the join criteria as well as the additional join criteria
Another takeaway : The AND T1.Month=T2.Month condition on the left join is redundant as the composite GOD key takes care of it explicitly.
cross join returns every row you can make by combining a row from each argument. (inner) join on returns the rows from cross join that satisfy its condition. Ie (inner) join on returns every row you can make that combines a row from each argument and that satisfies its condition.
left join on returns the rows from (inner) join on plus the rows you can make by extending unjoined left argument rows by null for columns of the right argument.
Notice that this is regardless of primary keys, unique column sets, foreign keys or any other constraints.
Here there are 2 rows in each argument so there are 2 X 2 = 4 rows in the cross join. But only 2 meet the condition--the ones where a row is combined with itself.
(If you left join a table with itself where the condition is the conjunction of one or more equalities of the left and right versions of a column and there are no nulls in those columns then every left argument row gets joined with at least itself from the right argument. So there are no unjoined left argument rows. So only the rows of the (inner) join on are returned.)
I have two tables, one with orders and another with order comments. I want to join these two tables. They are joined on a column "EID" which exists in both tables. I want all orders. I also want to see all comments with only certain criteria AND all other comments should be set to null. How do I go about this?
Orders Table
Order_Number
1
2
3
4
Comments Table
Comments
Cancelled On
Ordered On
Cancelled On
Cancelled On
In this example I would like to see for my results:
Order_Number | Comments
1 | Cancelled On
2 | Null
3 | Cancelled On
4 | Cancelled On
Thanks!
This seems like a rather trivial left join.
select o.order_number, c.comments
from orders o
left join comments c
on o.eid = c.eid
and (here goes your criteria for comments)
Tested on Oracle, there might be subtle syntax differences for other DB engines.
It depends on one condition:
Are you trying to SET the other comments to null? (replace the values in the table)
or
Are you trying to DISPLAY the other comments as null? (dont display them)
If you want to change the values in the table use
UPDATE `table` SET `column` = null WHERE condition;
otherwise use:
SELECT column FROM table JOIN othertable WHERE condition;
I have a single table of activities, some labelled 'Assessment' (type_id of 50) and some 'Counselling' (type_id of 9) with dates of the activities. I need to compare these dates to find how long people wait for counselling after assessment. The table contains rows for many people, and that is the primary key of 'id'. My problem is how to produce a result row with both the assessment details and the counselling details for the same person, so that I can compare the dates. I've tried joining the table to itself, and tried nested subqueries, I just can't fathom it. I'm using Access 2010 btw.
Please forgive my stupidity, but here's an example of joining the table to itself that doesn't work, producing nothing (not surprising):
Table looks like:
ID TYPE_ID ACTIVITY_DATE_TIME
----------------------------------
1 9 20130411
1 v 50 v 20130511
2 9 20130511
3 9 20130511
In the above the last two rows have only had assessment so I want to ignore them, and just work on the situation where there's both assessment and counselling 'type-id'
SELECT
civicrm_activity.id, civicrm_activity.type_id,
civicrm_activity.activity_date_time,
civicrm_activity_1.type_id,
civicrm_activity_1.activity_date_time
FROM
civicrm_activity INNER JOIN civicrm_activity AS civicrm_activity_1
ON civicrm_activity.id = civicrm_activity_1.id
WHERE
civicrm_activity.type_id=9
AND civicrm_activity_1.type_id=50;
I'm actually wondering whether this is in fact not possible to do with SQL? I hope it is possible? Thank you for your patience!
Sounds to me like you only want to get the ID numbers where you have a TYPE_ID entry of both 9 and 50.
SELECT DISTINCT id FROM civicrm_activity WHERE type_id = '9' AND id IN (SELECT id FROM civicrm_activity WHERE type_id = '50');
This will give you a list of id's that has entries with both type_id 9 and 50. With that list you can now go and get the specifics.
Use this SQL for the time of type_id 9
SELECT activity_date_time FROM civicrm_activity WHERE id = 'id_from_last_sql' AND type_id = '9'
Use this SQL for the time of type_id 50
SELECT activity_date_time FROM civicrm_activity WHERE id = 'id_from_last_sql' AND type_id = '50'
Your query looks OK to me, too. The one problem might be that you use only one table alias. I don't know, but perhaps Access treats the table name "specially" such that, in effect, the WHERE clause says
WHERE
civicrm_activity.type_id=9
AND civicrm_activity.type_id=50;
That would certainly explain zero rows returned!
To fix that, use an alias for each table. I suggest shorter ones,
SELECT A.id, A.type_id, A.activity_date_time,
B.type_id, B.activity_date_time
FROM civicrm_activity as A
JOIN civicrm_activity as B
ON A.id = B.id
WHERE A.type_id=9
AND B.type_id=50;