This is a Firebird database.
First Table
Contacts
Company_ID - job_title
Second Table
Client_id - Co_name
In contacts, I want to the job_title field to contain the co_name.
client_id and company_id are the same.
Co_name correspond to company_id as well as client_id.
this:
UPDATE Contacts
SET Contacts.Job_title = Clients.co_name
WHERE
company_id IN (
SELECT
client_id
FROM
clients
JOIN Contacts c ON Client_id = company_id
WHERE
record_status = 'A'
)
gives me an error as cannot find (clients.co_name)
this other option:
UPDATE Contacts
JOIN Clients ON Clients.Client_id = Contacts.Client_id
SET Contacts.Job_title = Clients.Client_name
gives me an error on JOIN
Any other ideas please?
Thank you all
Possibly already answered here: Update records in one table using another table's records as WHERE parameters - looks like it should work, but I'm not a Firebird expert.
The code from that answer (but look for more context, and alternative answers):
UPDATE Table1
SET Column1 = NULL
WHERE NOT EXISTS
(SELECT 1
FROM Table2
WHERE Table2.Column2 = Table1.Column2)
(couldn't flag question as duplicate because that question has no upvoted or accepted answer)
Related
I have got two tables:
create table student
(
studentid bigint primary key not null,
name varchar(200) not null
);
create table courseregistration
(
studentid bigint not null,
coursenamename varchar(200) not null,
isfinished boolean default false
);
--insert some data
insert into student values(1,'Dave');
insert into courseregistration values(1,'SQL',true);
Student is fetched with id, so it should be always returned in the result. Entry in the courseregistration is optional and should be returned if there are matching rows and those matching rows should be filtered on isfinished=false. This means I want to get the course regsitrations that are not finished yet. Tried to outer join student with courseregistration and filter courseregistration on isfinished=false. Note that, I still want to retrieve the student.
Trying this returns no rows:
select * from student
left outer join courseregistration using(studentid)
where studentid = 1
and courseregistration.isfinished = false
What I'd want in the example above, is a result set with 1 row student, but course rows null (because the only example has the isfinished=true). One more constraint though. If there is no corresponding row in courseregistration, there should still be a result for the student entry.
This is an adjusted example. I can tweak my code to solve the problem, but I really wonder, what is the "correct/smart way" of solving this in postgresql?
PS I have used the (+) in Oracle previously to solve similar issues.
Isn't this what you are looking for :
select * from student s
left outer join courseregistration cr
on s.studentid = cr.studentid
and cr.isfinished = false
where s.studentid = 1
db<>fiddle here
I have two tables, Users and Masters. Users are having User specific settingkey-value. Masters is having master settingkey-value. I want to display key-value from the two tables, where
if users do not have that particular key, need to take it from masters
2 if the users do not exists in the table, need to display all from masters key-value
if users having key-value, have to display users key-value
Example:
Inputs being - UserID and appID = 1.
I tried with left join combination, but not getting desired result if Users do not exists at all in the Users table.
Could you please give me some advise.
step-by-step demo:db<>fiddle
SELECT
COALESCE(m.app_id, u.app_id) as app_id,
COALESCE(m.setting_key, u.setting_key) as setting_key,
COALESCE(u.setting_value, m.setting_value) as setting_value -- 2
FROM
master_table m
FULL OUTER JOIN -- 1
user_table u
ON m.app_id = u.app_id AND m.setting_key = u.setting_key
WHERE COALESCE(m.app_id, u.app_id) = 1 -- 3
AND (u.user_id = 1 OR u.user_id IS NULL)
You need a FULL OUTER JOIN to join also data set that the other table does not contain
COALESCE(a, b) gives you the first non-null value. So, if a (here the user value) is available, it will be returned. Otherwise b (here the master value)
Filter by app_id and user_id; second needs to be filtered by user_id == NULL too, to get all setting_keys. Of course, you could use here COALESCE as well: COALESCE(u.user_id, 1) whereas the last 1 is the specific user_id you're asking
Edit: If User does not exist, give out the Masters values for app_id:
step-by-step demo:db<>fiddle:
SELECT DISTINCT ON (app_id, setting_key) -- 3
*
FROM (
SELECT
COALESCE(user_app_id, master_app_id) AS app_id, -- 2
COALESCE(user_setting_key, master_setting_key) AS setting_key,
COALESCE(user_setting_value, master_setting_value) AS setting_value,
user_id
FROM (
SELECT
app_id as master_app_id,
setting_key as master_setting_key,
setting_value as master_setting_value,
null as user_id,
null as user_app_id,
null as user_setting_key,
null as user_setting_value
FROM
master_table m
UNION -- 1
SELECT
*
FROM
master_table m
FULL OUTER JOIN
user_table u
ON m.app_id = u.app_id AND m.setting_key = u.setting_key
) s
) s
WHERE app_id = 1
AND (user_id = 2 OR user_id IS NULL)
ORDER BY app_id, setting_key, user_id NULLS LAST -- 3
This is a little more complicated. You need a separate data set for user_id == NULL which could be fetched. So, the NULL user represents the unknown user.
You can achieve this by adding the Master table with NULL values using an UNION.
Now you can create the expected columns with the COALESCE() functions as described above.
The third trick is using the DISTINCT ON clause on the app_id and the setting_key columns. When you ordered the NULL columns from the default UNION part in (1) last, then the DISTINCT ON will fetch the user record. However, when the user didn't exist, then the DISTINCT ON will fetch the default Master record.
I need to write a sql code that probably is very simple but I am very new to it.
I need to find all the records from one table that have matching id (but no more than one) from the other table. eg. one table contains records of the employees and the second one with employees' telephone numbers. i need to find all employees with only one telephone no
Sample data would be nice. In absence of:
SELECT
employees.employee_id
FROM
employees
LEFT JOIN
(SELECT distinct on(employee_id) employee_id FROM emp_phone) AS phone
ON
employees.employee_id = phone.employee_id
WHERE
phone.employee_id IS NOT NULL;
You need a join of the 2 tables, group by employee and the condition in the having clause:
SELECT e.employee_id, e.name
FROM employees e INNER JOIN numbers n
ON e.employee_id = n.employee_id
GROUP BY e.employee_id, e.name
HAVING COUNT(*) = 1;
If there can be more than a few numbers per employee in the table with the employees' telephone numbers (calling it tel), then it's cheaper to avoid GROUP BY and HAVING which has to process all rows. Find employees with "unique" numbers using a self-anti-join with NOT EXISTS.
While you don't need more than the employee_id and their unique phone number, you don't even have to involve the employee table at all:
SELECT *
FROM tel t
WHERE NOT EXISTS (
SELECT FROM tel
WHERE employee_id = t.employee_id
AND tel_number <> t.tel_number -- or use PK column
);
If you need additional columns from the employee table:
SELECT * -- or any columns you need
FROM (
SELECT employee_id AS id, tel_number -- or any columns you need
FROM tel t
WHERE NOT EXISTS (
SELECT FROM tel
WHERE employee_id = t.employee_id
AND tel_number <> t.tel_number -- or use PK column
)
) t
JOIN employee e USING (id);
The column alias in the subquery (employee_id AS id) is just for convenience. Then the outer join condition can be USING (id), and the ID column is only included once in the result, even with SELECT * ...
Simpler with a smart naming convention that uses employee_id for the employee ID everywhere. But it's a widespread anti-pattern to use employee.id instead.
Related:
JOIN table if condition is satisfied, else perform no join
I'm trying to create a policy in postgres that results in a column reference "person_id" is ambiguous.
To make a small, similar example let's describe 3 tables: person, group and group_member.
Person has: id, name
Group has: id, person_id and name
Group Member has: id, person_id, group_id
I've simplified my policy, but the relevant portion looks something like this:
CREATE POLICY insert_group_member ON public."group" FOR INSERT TO user_role WITH CHECK (
EXISTS (
SELECT * FROM "group" AS g
LEFT JOIN "group_member" AS gm ON
g.person_id = gm.person_id
AND g.id = gm.group_id
WHERE
g.id = id AND
gm.person_id = person_id AND
g.members_can_invite = TRUE
)
);
person_id in this case can refer to group.person_id or group_member.person_id from the sub-select, but what I really want it to be is the person_id coming from the "with check". This generally, works in other places.
Question: is there way to clearly specify that the person_id column comes from the policy and not from the select or the join. Note: I'd have expected that aliasing the table names solves this problem, but it seems to have not.
You should qualify all column references, like this:
...
WHERE g.id = "group".id
AND gm.person_id = "group".person_id
Long story short, I took over a project and a table in the database is in serious need of de-duping. The table looks like this:
supply_req_id | int | [primary key]
supply_req_dt | datetime |
request_id | int | [foreign key]
supply_id | int | [foreign key]
is_disabled | bit |
The duplication is exists with records having the same request_id and supply_id. I'd like to find a best practice way to de-dupe this table.
[EDIT]
#Kirk_Broadhurst, thanks for the question. Since supply_req_id is not referenced anywhere else, I would answer by saying keep the first, delete any subsequent occurances.
Happy Holidays
This creates a rank for each row in the (supply_req_dt, request_id) grouping, starting with 1 = lowest supply_req_id. Any dupe has a value > 1
;WITH cDupes AS
(
SELECT
supply_req_id,
ROW_NUMBER() OVER (PARTITION BY supply_req_dt, request_id ORDER BY supply_req_id) AS RowNum
FROM
MyTable
)
DELETE
cDupes
WHERE
RowNum > 1
Then add a unique constraint or INDEX
CREATE UNIQUE INDEX IXU_NoDupes ON MyTable (supply_req_dt, request_id)
Seems like there should be a command for this, but maybe that's because I'm used to a different database server. Here's the relevant support doc:
How to remove duplicate rows from a table in SQL Server
http://support.microsoft.com/kb/139444
You need to clarify your rule for determining which record to keep in the case of a 'match' - the most recent, the earliest, the one that has is_disabled true, or false?
Once you've identified that rule, the rest is fairly simple:
select the records you want to keep - the distinct records
join back to the original table to get the ids for those records.
delete everthing where not in the joined dataset.
So let's say you want to keep the most recent records of any 'duplicate' pair. Your query would look like this:
DELETE FROM [table] WHERE supply_req_id NOT IN
(SELECT supply_req_id from [table] t
INNER JOIN
(SELECT MAX(supply_req_dt) dt, request_id, supply_id
FROM [table]
GROUP BY request_id, supply_id) d
ON t.supply_req_dt = d.dt
AND t.request_id = d.request_id
AND t.supply_id = d.supply_id)
The catch is that if the supply_req_dt is also duplicated, then you'll be keeping both of the duplicates. The fix is to do another group by and select the top id
select MAX(supply_req_id), supply_req_dt, request_id, supply_id
group by supply_req_dt, request_id, supply_id
as an interim step. But if you don't need to do that, don't bother with it.