I need some advise for making a trigger that orders alphabetically after every insert.
Example:
Table COUNTRIES
ID 1, name 'Germany'
ID 2, name 'Bahamas'
ID 3, name 'Algeria'
Afterwards:
ID 1, name 'Algeria'
ID 2, name 'Bahamas'
ID 3, name 'Germany'
Any thoughts on how achieve this? Thank you.
PD: ORDER BY used on a SELECT statement will only order the rows for "aesthetical" purposes, the real rows would have no order whatsoever.
Finally, I have found an answer for this issue at http://sqlteam.com.
Maybe it will help some other users.
CREATE TRIGGER ORDER_COUNTRIES
AFTER INSERT
ON COUNTRIES
AS
BEGIN
UPDATE COUNTRIES
SET name = Table3.name
FROM Prueba Table1
JOIN (SELECT ID, seq = ROW_NUMBER() OVER (ORDER BY ID) FROM COUNTRIES) Table2
ON Table1.ID = Table2.ID
JOIN (SELECT name, seq = ROW_NUMBER() OVER (ORDER BY name) FROM COUNTRIES) Table3
ON Table2.seq = Table3.seq
END
Result:
ID 1, name 'Algeria'
ID 2, name 'Bahamas'
ID 3, name 'Germany'
Now the table gets properly ordered after every insert. So, if you SELECT either by using ORDER BY or not, your table will always be alphabetically ordered.
Answer found at http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=160974 from the user
"nigelrivett". All credit goes to him.
Related
The domain is:
company (id, name, adress)
employee (id, name, adress, company_id, expertise_id)
dependantrelative (id, name, employee_id)
expertise (id, name, class)
I want to know how to get the number of dependantrelatives of each employee who are unique experts in their respective companies.
The Query below does not return the correct answer. Can you help me?
SELECT DISTINCT dependantrelative.employee_id
, COUNT(*) AS qty_dependantrelatives
FROM dependantrelative
INNER JOIN employee
ON employee.id = dependantrelative.employee_id
GROUP BY dependantrelative.employee_id
I just tried out the Query below and it works, but I want to know if there is a faster and simple way of getting the answer.
SELECT employee.id
,COUNT(dependantrelative.employee_id) AS qty_dependantrelatives
FROM (
SELECT employee.company_id
, employee.expertise_id AS expert
, COUNT(employee.expertise_id)
FROM employee
GROUP BY employee.company_id
, employee.expertise_id
HAVING COUNT(employee.expertise_id)<2
) AS uniexpert
LEFT JOIN employee
ON employee.expertise_id = uniexpert.expert
LEFT JOIN salesorderdetail
ON dependantrelative.employee_id = employee.id
GROUP BY employee.id
ORDER BY employee.id
I have two tables(Table A and Table B) in a Postgres DB.
Both have "id" column in common. Table A has one column called "id" and Table B has three columns: "id, date, value($)".
For each "id" of Table A there exists multiple rows in Table B in the following format - (id, date, value).
For instance, for Table A with "id" as 1 if there exists following rows in Table B:
(1, 2018-06-21, null)
(1, 2018-06-20, null)
(1, 2018-06-19, 202)
(1, 2018-06-18, 200)
I would like to extract the most recent dated non-null value. For example for id - 1, the result should be 202. Please share your thoughts or let me know in case more info is required.
Here is the solution I went ahead with:
with mapping as ( select distinct table1.id, table2.value, table2.date, row_number() over (partition by table1.id order by table2.date desc nulls last) as row_number
from table1
left join table2 on table2.id=table1.id and table2.value is not null
)
select * from mapping where row_number = 1
Let me know if there is scope for improvement.
You may very well want an inner join, not an outer join. If you have an id in table1 that does not exist in table2 or that has only null values you will get NULL for both date and value. This is due to the how outer join works. What it says is if nothing in the right side table matches the ON condition then return NULL for each column in that table. So
with mapping as
(select distinct table1.id
, table2.value
, table2.date
, row_number() over (partition by table1.id order by table2.date desc nulls last) as row_number
from table1
join table2 on table2.id=table1.id and table2.value is not null
)
select *
from mapping
where row_number = 1;
See example of each here. Your query worked because all your test data satisfied the 1st condition of the ON condition. You really need test data that fails to see what your query does.
Caution: DATE and VALUE are very poor choice for a column names. Both are SQL standard reserved words, although not Postgres specifically. Further DATE is a Postgres data type. Having columns with names the same as datatype leads to confusion.
My table is somethingg like
CREATE TABLE table1
(
_id text,
name text,
data_type int,
data_value int,
data_date timestamp -- insertion time
);
Now due to a system bug, many duplicate entries are created and I need to remove those duplicated and keep only unique entries excluding data_date because it is a system generated date.
My query to do that is something like:
DELETE FROM table1 A
USING ( SELECT _id, name, data_type, data_value, MIN(data_date) min_date
FROM table1
GROUP BY _id, name, data_type, data_value
HAVING count(data_date) > 1) B
WHERE A._id = B._id
AND A.name = B.name
AND A.data_type = B.data_type
AND A.data_value = B.data_value
AND A.data_date != B.min_date;
However this query works, having millions of records in the table, I want a faster way for it. My idea is to create a new column with value as partition by [_id, name, data_type, data_value] or columns which are in group by. However, I could not find the way to create such column.
I would appretiate if any one may suggest a way to create such column.
Edit 1:
There is another thing to add, I don't want to use CTE or subquery for updating this new column because it will be same as my existing query.
The best way is simply creating a new table without duplicated records:
CREATE...
SELECT _id, name, data_type, data_value, MIN(data_date) min_date
FROM table1
GROUP BY _id, name, data_type, data_value;
Alternatively, you can create a rank and then filter, but a subquery is needed.
RANK() OVER (PARTITION BY your_variables ORDER BY data_date ASC) r
And then filter r=1.
I am creating some queries for my project, but I face some difficulties with the follow ones:
A SELECT statement containing a subquery to retrieve a list of Locations (location id and street_address) that have employees with higher salary than the average of their department. The list must contain the number of those employees and their total salary per location. Name these aggregates respectively "emp" and "totalsalary". The locations in the list must be ordered by location_id.
Select LOCATION_ID, STREET_ADDRESS
from HR.LOCATIONS IN
(Select Employee_id
from HR.Employees
Where Salary > round(avg(SALARY)))
order by location_id;
error: SQL command not properly ended
and the second query is the following
The JOB_HISTORY table can contain more than one entries for an employee who was hired more than once. Create a query to retrieve a list of Employees that were hired more than once. Include the columns EMPLOYEE_ID, LAST_NAME, FIRST_NAME and the aggregate "Times Hired".
SELECT FIRST_NAME,LAST_NAME,EMPLOYEE_ID,
count (*)as TIMES_HIRED
from HR.JOB_HISTORY, HR.EMPLOYEES
where EMPLOYEE_ID= LAST_NAME
having COUNT(*) >1;
error: not a single-group
Try these hope they help. I am making an assumption that employee table has Location_Id column. I am adding Employee_id to Group by to make sure you get correct TotalSalary:
Select LOCATION_ID, STREET_ADDRESS, Count(Employee_id) AS emp, SUM(salary) AS totalsalary
from HR.LOCATIONS INNER JOIN
(Select Employee_id, salary
from HR.Employees
Having Salary > round(avg(SALARY), 0)) AS Emp ON HR.LOCATION_ID = Emp.Location_ID
Group By LOCATION_ID, STREET_ADDRESS, Employee_id
order by location_id;
For the second question:
SELECT FIRST_NAME,LAST_NAME,EMPLOYEE_ID,
count(Employee_id) as TIMES_HIRED
from HR.JOB_HISTORY inner join HR.EMPLOYEES On JOB_HISTORY.Employee_id = Employees.Employee_id
Group By FIRST_NAME,LAST_NAME,EMPLOYEE_ID
Having count(Employee_id) >1;
I have a field that is similar to a MAC address in that the first part is a group ID and the second part is a serial number. My field is alphanumeric and 5 digits in length, and the first 3 are the group ID.
I need a query that gives me all distinct group IDs and the first serial number lexicographically. Here is sample data:
ID
-----
X4MCC
X4MEE
X4MFF
V21DD
8Z6BB
8Z6FF
Desired Output:
ID
-----
X4MCC
V21DD
8Z6BB
I know I can do SELECT DISTINCT SUBSTRING(ID, 1, 3) but I don't know how to get the first one lexicographically.
Another way which seems to have the same cost as the query by gbn:
SELECT MIN(id)
FROM your_table
GROUP BY SUBSTRING(id, 1, 3);
SELECT
ID
FROM
(
SELECT
ID,
ROW_NUMBER() OVER (PARTITION BY SUBSTRING(ID, 1, 3) ORDER BY ID) AS rn
FROM MyTable
) oops
WHERE
rn = 1