TableA:
ID RES_ID NAME
--------------------
1 3 (null)
2 1 (null)
3 3 (null)
TableB:
RES_ID AREA_NAME
-------------------
3 India
1 Japan
3 India
TableC:
AREA_NAME CITY_NAME
-----------------------
India Delhi
Japan Tokyo
England London
I want to join the above three tables and update the CITY_NAME in TableC to NAME in TableA using DB2.
Please help me to sort it out.
I have tried the below code but it is not working.
MERGE INTO TableA A
USING TableB B, TableC C
ON A.RES_ID= B.RES_ID
AND B.AREA_NAME = C.AREA_NAME
WHEN MATCHED
THEN UPDATE SET A.NAME = C.CITY_NAME;
It displays error message.I want the output as follows,
Updated TableA:
ID RES_ID NAME
--------------------
1 3 Delhi
2 1 Tokyo
3 3 Delhi
Thanks in advance!
You could try this:
update A set name = c.name from tableA A
inner join tableB B ON A.RES_ID= B.RES_ID
inner join tableC C on B.AREA_NAME = C.AREA_NAME
The MERGE operator is used to update records when the disired record exists otherwise insert the record. But you already have the record, you only need to update a field. Hence you need an update query
Related
I have two tables in HIVE, "orders" and "customers". I want to get top n user names of users who placed most orders (in status "CLOSED"). Orders table has key order_customer_id, column order_status and customers has key customer_id and name consists of 2 columns customer_fname and customer_lname.
ORDERS
order_customer_id, order_status
1,CLOSED
2,CLOSED
3,INPROGRESS
1,INPROGRESS
1,CLOSED
2,CLOSED
CUSTOMERS
customer_id, customer_fname, customer_lname
1,Mickey, Mouse
2,Henry, Ford
3,John, Doe
I tried this code:
select c.customer_id, count(o.order_customer_id) as COUNT, concat(c.customer_fname," ",c.customer_lname) as FULLNAME from customers c join orders o on c.customer_id=o.order_customer_id where o.order_status='CLOSED' group by c.customer_id,FULLNAME order by COUNT desc limit 10;
this does not work - returns error.
I was able to get the result by first creating a 3rd table:
create table id_sum as select o.order_customer_id,count(o.order_id) as COUNT from orders o join customers c on c.customer_id=o.order_customer_id where order_status='CLOSED' group by o.order_customer_id;
1833 6
5493 5
1363 5
1687 5
569 4
1764 4
1345 4
Then I joined the tables:
select s.*,concat(c.customer_fname," " ,c.customer_lname) from id_sum s join customers c on s.order_customer_id = c.customer_id order by count desc limit 20;
This resulted in desired output:
customer_id, order_count, full_name
1833 6 Ronald Smith
5493 5 Mary Cochran
1363 5 Kathy Rios
1687 5 Jerry Ellis
569 4 Mary Frye
1764 4 Megan Davila
1345 4 Adam Wilson
Is there a way how to write it in one command or more effectively?
The subquery with alias sq creates a relation with two columns order_count and customer_id calculating for each customer_id the total number of orders. This is then joined with the CUSTOMERS table. The result is sorted descending and limited to (the top) 10 rows.
SELECT c.customer_id, sq.order_count, concat(c.customer_fname," " ,c.customer_lname) as full_name
FROM CUSTOMERS c JOIN (
SELECT COUNT(*) as order_count, order_customer_id FROM ORDERS
WHERE order_status = 'CLOSED'
GROUP BY order_customer_id
) sq on c.customer_id = sq.order_customer_id
ORDER BY sq.order_count desc LIMIT 10
;
The idea is to use a subquery instead of a third table.
I have this datatables:
table1
id category
-------------
1 a
2 b
3 c
table2
id heading category_id
----------------------
1 name 1
2 adddress 2
3 phone 3
4 email 1
I want to group this table and display the latest data for that the following query was I used:
SELECT news.id,news.image,news.heading,news.description,
news.date,news.category_id,categories.category
FROM `news`
INNER JOIN categories On news.category_id=categories.id
group by category_id
But I didnt get the latest data that I entered.
Try the query below:
SELECT *
FROM table2 AS tb2 LEFT JOIN table1 AS tb1 ON tb2.category_id = tb1.id
ORDER BY tb1.id
GROUP BY tb2.category_id
This shows some sample data that I might have (real data is much larger):
table1:
date forename surname PK
1998 john harry
1928 fred kale
table2:
date forename surname PK
1998 john harry 2
1928 fred kale 98
I need to compare table2 with table1 and if they match then I need to add the same PK from table2 into table1 to form a relation.
EDIT: I would like to add that in table1, the "people" can appear twice but only once in table2.
PostgreSQL:
UPDATE table1
SET FK = table2.PK
FROM table2
WHERE
table1.date = table2.date
AND table1.forename = table2.forename
AND table1.surname = table2.surname
SQL Server
UPDATE t1
SET FK = t2.PK
FROM
table1 t1 INNER JOIN table2 t2
ON t1.date = t2.date
AND t1.forename = t2.forename
AND t1.surname = t2.surname
I have a scenario where I am joining three tables and getting the results.
My problem is i have apply limit for joined table.
Take below example, i have three tables 1) books and 2) Customer 3)author. I need to find list of books sold today with author and customer name however i just need last nth customers not all by passing books Id
Books Customer Authors
--------------- ---------------------- -------------
Id Name AID Id BID Name Date AID Name
1 1 1 ABC 1 A1
2 2 1 CED 2 A2
3 3 2 DFG
How we can achieve this?
You are looking for LATERAL.
Sample:
SELECT B.Id, C.Name
FROM Books B,
LATERAL (SELECT * FROM Customer WHERE B.ID=C.BID ORDER BY ID DESC LIMIT N) C
WHERE B.ID = ANY(ids)
AND Date=Current_date
DNO DNAME
----- -----------
1 Research
2 Finance
EN ENAME CITY SALARY DNO JOIN_DATE
-- ---------- ---------- ---------- ---------- ---------
E1 Ashim Kolkata 10000 1 01-JUN-02
E2 Kamal Mumbai 18000 2 02-JAN-02
E3 Tamal Chennai 7000 1 07-FEB-04
E4 Asha Kolkata 8000 2 01-MAR-07
E5 Timir Delhi 7000 1 11-JUN-05
//find all departments that have more than 3 employees.
My try
select deptt.dname
from deptt,empl
where deptt.dno=empl.dno and (select count(empl.dno) from empl group by empl.dno)>3;
here is the solution
select deptt.dname
from deptt,empl
where deptt.dno=empl.dno
group by deptt.dname having count(1)>3;
select
*
from departments d
inner join (
select dno from employees group by dno having count(*) > 3
) e on d.dno = e.dno
There are many approaches to this problem but almost all will use GROUP BY and the HAVING clause. That clause allows you to filter results of aggregate functions. Here it is used to choose only those records where the count is greater than 3.
In the query structure used above the group by is handled on the employee table only, then the result (which is known as a derived table) is joined by an INNER JOIN to the departments table. This inner join only allows matching records so this has the effect of filtering the departments table to only those which have a count() of greater than 3.
An advantage of this query structure is fewer records are joined, and also that all columns of the departments table are available for reporting. Disadvantage of this structure is the the count() of employees per department isn't visible.