Assuming I have a table with 3 columns, ID, Name, City and I want to use named query to return rows with unique city..can it be done?
Are you asking whether it is possible to write a query that will return the cities that appear in exactly one row, in a table that has ID/Name/City triplets where there could be multiple rows for the same city but with different names?
If so, it would depend on the database engine behind the scenes - but you could try things like:
with candidates (city, num) as (
select city, count(*) from table
group by city
)
select city from candidates where num = 1
Or
select t1.city from table t1
where not exists (
select * from table t2
where t2.city = t1.city and t2.id <> t1.id
)
where table is your table with these triplets.
Related
I have Table1 with columns:
Fname,Sname
Table 2 with columns:
Fname,Lname
Now,in a query I want to take all the values from these two tables (First names and last names [Sname in table 1 is Lname]) and return to one columns.
Basically I want to create column to get list of participants which include everyone from these two tables.
Is it possible?
Both the tables are joined indirectly via third table.
You can use UNION ALL will give all the rows from both tables.
SELECT
Fname,
Sname,
CONCAT(Fname,Sname) AS FSname
FROM table1
UNION ALL
SELECT
Fname,
Lname,
CONCAT(Fname,Lname)
FROM table2;
The column names are taken from the first SELECT.
If you use UNION and not UNION ALL rows in table2 which are duplicates of table1 will be omitted, but it can run slower as the values have to be compared.
You can use the third table and LEFT JOIN onto both tables and use COALESCE which returns the first argument which is not null.
SELECT
COALESCE(t1.Fname,t2.Fname),
COALESCE(t1.Sname,t2.Lname),
CONCAT(
COALESCE(t1.Fname,t2.Fname),
COALESCE(t1.Sname,t2.Lname)
) AS FSname
FROM third_table t3
LEFT JOIN table1 t1
ON t1.id = t3.id
LEFT JOIN table2 t2
ON t2.id = te.id;
table image
I have this table that I need to sort in the following way:
need to rank Departments by Salary;
need to show if Salary = NULL - 'No data to be shown' message
need to add total salary paid to the department
need to count people in the department
SELECT RANK() OVER (
ORDER BY Salary DESC
)
,CASE
WHEN Salary IS NULL
THEN 'NO DATA TO BE SHOWN'
ELSE Salary
,Count(Fname)
,Total(Salary) FROM dbo.Employees
I get an error saying:
Column 'dbo.Employees.Salary' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
Why so?
Column 'dbo.Employees.Salary' is invalid in the select list because it
is not contained in either an aggregate function or the GROUP BY
clause.
Why so?
The aggregate functions are returning a single value for the whole table, you can't SELECT a field alongside them it doesn't makes sense. Like say, you have a students table you apply Sum(marks) for the whole students table, and you are then also selecting student's name Select studentname in your query. Which student's name will the database engine select? Confusing
Column "invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause"
I tried this-
using inner query
SELECT RANK() OVER (ORDER BY SAL DESC) RANK,FNAME,DEPARTMENT
CASE
WHEN SAL IS NULL THEN 'NO DATA TO BE SHOWN'
ELSE SAL
END
FROM
(SELECT COUNT(FNAME) FNAME, SUM(SALARY) SAL, DEPARTMENT
FROM TESTEMPLOYEE
GROUP BY DEPARTMENT) t
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 have a temp table with multiple rows in it and each row has a column called Categories; which contains a very simple json array of ids for categories in a different table.
A few example rows of the temp table:
Id Name Categories
---------------------------------------------------------------------------------------------
'539f7e28-143e-41bb-8814-a7b93b846007' Test 1 ["category1Id", "category2Id", "category3Id"]
'f29e2ecf-6e37-4aa9-aa56-4a351d298bfc' Test 2 ["category1Id", "category2Id"]
'34e41a0a-ad92-4cd7-bf5c-8df6bfd6ed5c' Test 3 NULL
Now what I would like to do is to select all of the category ids from all of the rows in the temp table.
What I have is the following and it's not working as it's giving me the error of :
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
SELECT
c.Id
,c.[Name]
,c.Color
FROM
dbo.Category as c
WHERE
c.Id in (SELECT [value] FROM OPENJSON((SELECT Categories FROM #TempTable)))
and c.IsDeleted = 0
Which I guess it makes sense that's failing on that because I'm selecting multiple rows and needing to parse each row's respective category ids json. I'm just not sure what to do/change to give me the results that I want. Thank you in advance for any help.
You'd need to use CROSS APPLY like so:
SELECT id ,
name ,
t.Value AS category_id
FROM #temp
CROSS APPLY OPENJSON(categories, '$') t;
And then, you can JOIN to your Categories table using the category_id column, something like this:
SELECT id ,
name ,
t.Value AS category_id,
c.*
FROM #temp
CROSS APPLY OPENJSON(categories, '$') t
LEFT JOIN Categories c ON c.Id = t.Value
I am trying to removing duplicate values which, for some reason, was imported in a specific Table.
There is no Primary Key in this table.
There is 27797 unique records.
Select distinct txdate, plunumber from itemaudit
Give me the correct records, but only displays the txdate, plunumber of course.
If it was possible to select all the fields but only select the distinct of txdate,plunumber I could export the values, delete the duplicated ones and re-import.
Or if its possible to delete the distinct values from the entire table.
If you select the distinct of all fields the value is incorrect.
To get all information on the duplicates, you simply need to query all information for the duplicate rows using a JOIN:
SELECT b.*
FROM (SELECT COUNT(*) as cnt, txdate, plunumber
FROM itemaudit
GROUP BY txdate, plunumber
HAVING COUNT(*) > 1) a
INNER JOIN itemaudit b ON a.txdate = b.txdate AND a.plunumber = b.plunumber
DELETE FROM itemaudit t1
WHERE EXISTS (
SELECT 1 FROM itemaudit t2
WHERE t1.txdate = t2.txdate and t1.plunumber = t2.plunumber
AND t1.RDB$DB_KEY < t2.RDB$DB_KEY
);