I have following query that works correctly:
select * from myTable a where a.company is null and exists (select b.company from myTable b where b.id = a.id and b.office_id = a.office_id and b.company is not null);
Now, I also want to display the field value b.company from the subquery next to the fields from myTable a.
How do I get this done?
Thank you and best regards
If you want results from multiple tables you should join the tables together.
Since you want only records from A that exist in B, you need to use an outer JOIN returning all records from A and only those matching in B. But then you want to exclude all those records from A that were not found in B.
SELECT *, b.company
FROM myTable a
LEFT JOIN myTable B
ON b.id = a.id
and b.office_id = a.office_id
and b.company_ID is not null
WHERE a.company is null
and B.ID is not null and B.office_ID is not null --this handles the exists part.
Related
I am currently retrieving data from multiple tables using a cus_id as the initial query. From here I have multiple tables that can have various rows of data that I would like to retrieve and use GROUP_CONCAT to return this data in a single row. At the moment, my query is returning duplicate data based on the max number of rows returned by one of the group concats.
SELECT a.id,c.x,c.y,c.z
GROUP_CONCAT(a.column_a) AS aca,
GROUP_CONCAT(a.column_b) AS acb,
GROUP_CONCAT(b.column_a) AS bca,
GROUP_CONCAT(b.column_b) AS bcb,
FROM `table_a` a
INNER JOIN `table_b` b ON a.id = b.id
INNER JOIN `table_c` c ON a.id = c.id
WHERE a.id = ?
Also, in this scenario, what is the correct join method to use. I am expecting all the fields I am requesting to have some sort of data.
Problem was resolved by using sub queries to isolate the GROUP_CONCAT requests. This allowed me to get only the data I wanted without duplicate results manipulated by other JOIN requests.
SELECT a.id,c.x,c.y,c.z
(SELECT GROUP_CONCAT(column_a) FROM table_a) AS aca,
(SELECT GROUP_CONCAT(column_b) FROM table_a) AS acb,
(SELECT GROUP_CONCAT(column_a) FROM table_b) AS bca,
(SELECT GROUP_CONCAT(column_b) FROM table_b) AS bcb,
FROM table_a a
INNER JOIN `table_c` c ON a.id = c.id
WHERE a.id = ?
Aggregate before joining. Somthing along the lines of:
select
a.*,
b.grp_a,
b.grp_b,
c.grp_x,
b.grp_y
from table_a a
join
(
select
a_id,
group_concat(a order by b_id) as grp_a,
group_concat(b order by b_id) as grp_b
from table_b
group by a_id
) b on b.a_id = a.id
join
(
select
a_id,
group_concat(x order by c_id) as grp_x,
group_concat(y order by c_id) as grp_y
from table_c
group by a_id
) c on c.a_id = a.a_id
order by a.a_id;
I have 2 tables in my SQL database. Let's call them Table A and Table B.
I have joined both the tables using left join on ID = AID. Table A has a field by name ID and Table B has field AID and Price.
The problem is Table B can have multiple prices for the ID present in Table A.
The requirement is - If only one price is present in Table B corresponding to ID in table A then it should return that price.
If more than one price is present in table B for an ID in table A then I should get the price as Zero/null.
Query -
SELECT DISTINCT A.ID,B.Price
from A
left join B
on A.ID = B.AID
where "some condition"
Use Count() with Over() window function to find the count of records for each ID then based on count return the price
Try this way
SELECT DISTINCT A.ID,
case when count(1) over(partition by A.ID) > 1 then NULL else B.Price end
from A
left join B
on A.ID = B.AID
For Mysql
SELECT DISTINCT a.id,
CASE
WHEN c.aid IS NULL THEN NULL
ELSE b.price
END
FROM a
LEFT JOIN b
ON a.id = b.aid
LEFT JOIN (SELECT aid
FROM b
GROUP BY aid
HAVING Count(1) = 1) c
ON a.id = c.aid
For SQL Server (should work for MySQL too). One sub-query (you can put in CTE) that shows only AIDs that have only one price:
SELECT A.ID,
B.Price
FROM A
LEFT JOIN (
SELECT AID
FROM B
GROUP BY AID
HAVING COUNT(Price) = 1
) as C
ON C.AID = A.ID
LEFT JOIN B
ON C.AID = B.AID
Use below query. It should work.
SELECT A.ID, o.Price
FROM A
OUTER APPLY
(
SELECT IIF(COUNT(B.Price)>1,NULL,MAX(B.Price)) AS Price
FROM B
WHERE B.AID = A.ID
) AS o;
SELECT *
FROM table_a
LEFT JOIN table_b ON (table_b.id = table_a.id)
WHERE table_b.created BETWEEN ? AND ?
AND table_b.manager IN(
SELECT DISTINCT (b.id)
FROM table_b a
INNER JOIN table_b b ON a.manager = b.id
AND b.user_level > 0
AND b.id != 1
)
How can I remove the sub query and use JOINS instead in the above query
Thanks
MySQL 5.5 (and lower version)'s optimizer produces a DEPENDENT SUBQUERY for IN (SELECT ...) which means every matching row is found, IN(SELECT ...) is evaluated that makes select slow.
Simple optimization of your query is make inline view as follows:
SELECT *
FROM table_a LEFT JOIN table_b ON (table_b.id = table_a.id)
INNER JOIN (
SELECT DISTINCT b.id AS id
FROM table_b a
INNER JOIN table_b b ON a.manager = b.id
AND b.user_level > 0
AND b.id != 1
) x ON table_b.manager = x.id
WHERE table_b.created BETWEEN ? AND ?
AND x.id IS NOT NULL;
I think avobe query would produce as same as your own.
Last, DISTINCT is not a function. please use SELECT DISTINCT b.id rather SELECT DISTINCT (b.id)
I have this query that will work if there is data in both tables
SELECT a.location, b.location, a.refno, b.note
FROM (
SELECT location, refno
FROM tableA WHERE refno = '1234'
) a, (
SELECT location, note FROM tableB WHERE note = LN1234567
) b
but some of the time there may not be data in either one of the tables for the specific match in the WHERE clauses
I've also tried this which does work but i need the data on one row
SELECT location, refno
FROM tableA
WHERE refno = '1234'
UNION
SELECT location, note
FROM tableB
WHERE note = 'LN1234567'
My question is, is there an alternative way of querying both tables so I get one row with data from either OR both tables?
You can try with:
SELECT MAX(location_a) AS location_a,
MAX(refno_a) AS refno_a,
MAX(location_b) AS location_b,
MAX(refno_b) AS refno_b
FROM (
SELECT location AS location_a,
refno AS refno_a,
NULL AS location_b,
NULL AS refno_b
FROM tableA
WHERE refno = '1234'
UNION ALL
SELECT NULL AS location_a,
NULL AS refno_a,
location AS location_b,
location AS refno_b
FROM tableB
WHERE note = 'LN1234567') s
Assuming you want matching locations on both side, you want a left join. Here is a simplified version:
SELECT a.location, b.location, a.refno, b.note
FROM tableA a LEFT JOIN
tableB b
on a.location = b.location
WHERE a.refno = '1234' and b.note = 'LN1234567';
If you actually want a cross join (different locations on the same row) and still want results, I think you need a union all:
SELECT a.location, b.location, a.refno, b.note
FROM tableA a CROSS JOIN
tableB b
WHERE a.refno = '1234' and b.note = 'LN1234567'
UNION ALL
SELECT a.location, NULL, a.refno, NULL
FROM tableA
WHERE NOT EXISTS (SELECT 1 FROM tableB b WHERE b.note = 'LN1234567');
If inner join requires that a row exists, what's the opposite of it without having to do a sub query of NOT EXISTS?
I replaced
AND NOT EXISTS (
SELECT
*
FROM topic_read_assoc
WHERE topic_id = topic.id
AND member_id = ".$this->tru->application->currentMember->getId()."
)
with
OUTER JOIN topic_read_assoc ON (
topic_read_assoc.topic_id = topic.id AND
member_id = member_id = ".$this->tru->application->currentMember->getId()."
)
and it's not producing the same results as the first query (which works)
OUTER JOIN with a WHERE field IS NULL
Example:
SELECT A.name FROM A INNER JOIN B on A.id = B.id
Select those names in A whose id fields exist in B
Opposite:
SELECT A.name FROM A OUTER JOIN B on A.id = B.id WHERE B.id IS NULL
Select those names in A whose id fields do not exist in B
i think select on outer join is slow, because dbms left join first,then right join and delete the repeated rows.So I suggest you to select on the left join,then right join,make a intersect.It is better not operate on any join,because the view doesnt have index.