data in mark table:
VALUE SUBJECT_ID STUDENT_ID
---------- ---------- ----------
73 1 6
98 1 1
68 2 1
75 3 6
78 5 6
75 1 7
69 4 7
I have tried the following code, it executes successfully and gives the desired result, however it fails to clear one test case and IDK why?
SELECT DISTINCT
student_id,
min(value) as MINIMUM_MARK
FROM mark
WHERE value IN (
SELECT
min(value)
FROM mark
GROUP BY (subject_id)
)
GROUP BY (student_id)
ORDER BY MINIMUM_MARK;
The expected output is :
STUDENT_ID MINIMUM_MARK
---------- ------------
1 68
7 69
6 73
You can simply use group by as following:
Select student_id,
Min(value) as minimum_marks
From marks
Group by student_id
Order by minimum_marks
Cheers!!
I would just use ROW_NUMBER here:
WITH cte AS (
SELECT m.*, ROW_NUMBER() OVER (PARTITION BY STUDENT_ID ORDER BY "VALUE" DESC) rn
FROM mark
)
SELECT STUDENT_ID, MARK
FROM cte
WHERE rn = 1
ORDER BY MARK;
Related
I have 2 tables - tab1 , tab2 with following data
tab1 data:
OID Label
1 MX1
1 MX2
1 MX3
2 MX4
2 MX5
tab2 data:
OID ID Label
1 5678
1 2347
1 9687
2 4567
2 3455
The join condition between these two tables is oid column.I need to create a process which will update Label column from tab1 to Label column of tab2.It doesn't matter which label gets assigned to which record of tab2 for a particular oid. The only check that needs to happen is that both the tables should have same number of records for an oid.The final outcome should be the following
tab2 data:
OID ID Label
1 5678 MX1
1 2347 MX2
1 9687 MX3
2 4567 MX4
2 3455 MX5
Again, it doesn't matter which label gets assigned to tab2 for a particular oid,but the same label cannot be repeated for a particular oid.What would be the best way to write a code for this requirement?
Here is a sql solution:
merge into tab2
using
(
select t2."id" as ide,t1."label" labela from
(select rownum n,"label","oid" from tab1 order by "oid")t1,
(select rownum n, a2.* from tab2 a2 order by "oid")t2
where t1.n=t2.n and
t1."oid"=t2."oid"
) tb4
on (tab2."id" = tb4.ide)
when matched then
update set tab2."label" = tb4.labela;
Result:
oid| id | label
-----------------
1 5678 mx1
1 2347 mx2
1 9687 mx3
2 4567 mx4
2 3455 mx5
Sample tables:
SQL> select * from tab1 order by oid, label;
OID LAB
---------- ---
1 mx1
1 mx2
1 mx3
2 mx4
2 mx5
SQL> select * from tab2 order by oid, id;
OID ID LAB
---------- ---------- ---
1 2347
1 5678
1 9687
2 3455
2 4567
SQL>
This is query that returns desired result:
SQL> with
2 t1 as (select oid, label, rowid rwid,
3 row_number() over (partition by oid order by label) rn
4 from tab1
5 ),
6 t2 as (select oid, id, rowid rwid,
7 row_number() over (partition by oid order by id) rn
8 from tab2
9 )
10 select b.oid, b.id, a.label
11 from t1 a join t2 b on a.oid = b.oid and a.rn = b.rn;
OID ID LAB
---------- ---------- ---
1 2347 mx1
1 5678 mx2
1 9687 mx3
2 3455 mx4
2 4567 mx5
SQL>
A few options I tried: correlated update won't work because of
ORA-01779: cannot modify a column which maps to a non key-preserved table
SQL> update (
2 with
3 t1 as (select oid, label, rowid rwid,
4 row_number() over (partition by oid order by label) rn
5 from tab1
6 ),
7 t2 as (select oid, id, rowid rwid, label,
8 row_number() over (partition by oid order by id) rn
9 from tab2
10 )
11 select b.oid, b.id, b.label b_label, a.label a_label
12 from t1 a join t2 b on a.oid = b.oid and a.rn = b.rn
13 )
14 set b_label = a_label;
set b_label = a_label
*
ERROR at line 14:
ORA-01779: cannot modify a column which maps to a non key-preserved table
SQL>
MERGE won't work because of
ORA-01732: data manipulation operation not legal on this view
SQL> merge into
2 (select oid, id, label, row_Number() over (partition by oid order by id ) rn from tab2) b
3 using (select oid, label, row_number() over (partition by oid order by label) rn from tab1) a
4 on (a.oid = b.oid and
5 a.rn = b.rn)
6 when matched then update set
7 b.label = a.label;
(select oid, id, label, row_Number() over (partition by oid order by id ) rn from tab2) b
*
ERROR at line 2:
ORA-01732: data manipulation operation not legal on this view
SQL>
Merge would accept a view (created with create view ...), but a view has to be updateable; this one can't be because it contains analytic function.
What's left is a PL/SQL procedure:
SQL> begin
2 for cur_r in (with
3 t1 as (select oid, label, rowid rwid,
4 row_number() over (partition by oid order by label) rn
5 from tab1
6 ),
7 t2 as (select oid, id, rowid rwid,
8 row_number() over (partition by oid order by id) rn
9 from tab2
10 )
11 select b.rwid, a.label
12 from t1 a join t2 b on a.oid = b.oid and a.rn = b.rn
13 )
14 loop
15 update tab2 b set
16 b.label = cur_r.label
17 where b.rowid = cur_r.rwid;
18 end loop;
19 end;
20 /
PL/SQL procedure successfully completed.
SQL> select * from tab2 order by oid, id;
OID ID LAB
---------- ---------- ---
1 2347 mx1
1 5678 mx2
1 9687 mx3
2 3455 mx4
2 4567 mx5
SQL>
Maybe someone has another idea; I'd like to see it & learn something new.
I'm new to PL SQL and have to write a function, which has customer_id as an input and has to output a product_name of the best selling product for that customer_id.
The schema looks like this:
I found a lot of simple examples where it includes two tables, but I can't seem to find one where you have to do multiple joins and use a function, while selecting only the best selling product.
I could paste a lot of very bad code here and how I tried to approach this, but this seems to be a bit over my head for current knowledge, since I've been learning PL SQL for less than 3 days now and got this task.
With some sample data (minimal column set):
SQL> select * from products order by product_id;
PRODUCT_ID PRODUCT_NAME
---------- ----------------
1 BMW
2 Audi
SQL> select * From order_items;
PRODUCT_ID CUSTOM QUANTITY UNIT_PRICE
---------- ------ ---------- ----------
1 Little 100 1
1 Little 200 2
2 Foot 300 3
If we check some totals:
SQL> select o.product_id,
2 o.customer_id,
3 sum(o.quantity * o.unit_price) total
4 from order_items o
5 group by o.product_id, o.customer_id;
PRODUCT_ID CUSTOM TOTAL
---------- ------ ----------
2 Little 400
1 Little 100
2 Foot 900
SQL>
It says that
for customer Little, product 2 was sold with total = 400 - that's our choice for Little
for customer Little, product 1 was sold with total = 100
for customer Foot, product 2 was sold with total = 900 - that's our choice for Foot
Query might then look like this:
temp CTE calculates totals per each customer
rank_them CTE ranks them in descending order per each customer; row_number so that you get only one product, even if there are ties
finally, select the one that ranks as the highest
SQL> with
2 temp as
3 (select o.product_id,
4 o.customer_id,
5 sum(o.quantity * o.unit_price) total
6 from order_items o
7 group by o.product_id, o.customer_id
8 ),
9 rank_them as
10 (select t.customer_id,
11 t.product_id,
12 row_number() over (partition by t.customer_id order by t.total desc) rn
13 from temp t
14 )
15 select * From rank_them;
CUSTOM PRODUCT_ID RN
------ ---------- ----------
Foot 2 1 --> for Foot, product 2 ranks as the highest
Little 2 1 --> for Little, product 1 ranks as the highest
Little 1 2
SQL>
Moved to a function:
SQL> create or replace function f_product (par_customer_id in order_items.customer_id%type)
2 return products.product_name%type
3 is
4 retval products.product_name%type;
5 begin
6 with
7 temp as
8 (select o.product_id,
9 o.customer_id,
10 sum(o.quantity * o.unit_price) total
11 from order_items o
12 group by o.product_id, o.customer_id
13 ),
14 rank_them as
15 (select t.customer_id,
16 t.product_id,
17 row_number() over (partition by t.customer_id order by t.total desc) rn
18 from temp t
19 )
20 select p.product_name
21 into retval
22 from rank_them r join products p on p.product_id = r.product_id
23 where r.customer_id = par_customer_id
24 and r.rn = 1;
25
26 return retval;
27 end;
28 /
Function created.
SQL>
Testing:
SQL> select f_product ('Little') result from dual;
RESULT
--------------------------------------------------------------------------------
Audi
SQL> select f_product ('Foot') result from dual;
RESULT
--------------------------------------------------------------------------------
Audi
SQL>
Now, you can improve it so that you'd care about no data found issue (when customer didn't buy anything), ties (but you'd then return a collection or a refcursor instead of a scalar value) etc.
[EDIT] I'm sorry, ORDERS table has to be included into the temp CTE; your data model is correct, you don't have to do anything about it - my query was wrong (small screen + late hours issue; not a real excuse, just saying).
So:
with
temp as
(select i.product_id,
o.customer_id,
sum(i.quantity * i.unit_price) total
from order_items i join orders o on o.order_id = i.order_id
group by i.product_id, o.customer_id
),
The rest of my code is - otherwise - unmodified.
Currently, I have a table MY_TABLE like below:
ID ACCT_TYPE CREDIT_AMT DEBIT_AMT
-- --------- ---------- ---------
1 CDT_01 4 (null)
1 DBT_01 (null) 6
One ID can have multiple ACCT_TYPE like above, and each type has its own amount.
I want to just select the row which has ACCT_TYPE like 'CDT_%' but also the total_amount column which is the total of credit_amt and debit_amt column for the same ID.
My expected output like below:
ID ACCT_TYPE TOTAL_AMT
-- --------- ---------
1 CDT_01 10
I tried with this select statement below but it's no use, I think it's because of different ACCT_TYPE:
Select ID, ACCT_TYPE, SUM(NVL(CREDIT_AMT, 0) + NVL(DEBIT_AMT, 0)) TOTAL_AMT
FROM MY_TABLE WHERE ACCT_TYPE LIKE 'CDT_%' GROUP BY ID, ACCT_TYPE;
Here is the output of the select statement above:
ID ACCT_TYPE TOTAL_AMT
-- --------- ---------
1 CDT_01 4
I just begin to learn some query so I don't know is it really possible to get my expected output.
One way to do it is like below:
with inputs (ID, ACCT_TYPE, CREDIT_AMT, DEBIT_AMT) as
(
select 1, 'CDT_01', 4, null from dual union all
select 1, 'DBT_01', null, 6 from dual
),
prep as
(
select t.*, sum(nvl(credit_amt,0)) over (partition by id) + sum(nvl(debit_amt,0)) over (partition by id) as sum_per_id
from inputs t
)
select id, acct_type, sum_per_id
from prep
where acct_type like 'CDT_%';
Output:
A correlated subquery might be one option; sample data (thank you, #Ranagal) in lines #1 - 5; query that does the job begins at line #6.
SQL> with inputs (ID, ACCT_TYPE, CREDIT_AMT, DEBIT_AMT) as
2 (
3 select 1, 'CDT_01', 4, null from dual union all
4 select 1, 'DBT_01', null, 6 from dual
5 )
6 select a.id,
7 a.acct_type,
8 (select sum(nvl(b.credit_amt, 0)) +
9 sum(nvl(b.debit_amt , 0))
10 from inputs b
11 where b.id = a.id
12 ) total_amt
13 from inputs a
14 where acct_type like 'CDT%';
ID ACCT_T TOTAL_AMT
---------- ------ ----------
1 CDT_01 10
SQL>
If we have table Employees
EMP_ID ENAME SALARY DEPT_ID
1 abc 1000 10
2 bca 1050 10
3 dsa 2000 20
4 zxc 3000 30
5 bnm 5000 30
6 rty 5050 30
I want to get the rank of the salary with before 2 values and after 2 values including the given rank
Like if I give rank 4 it should give ranks 2,3,4,5,6 details.
output should be
5 bnm 5000 30
4 zxc 3000 30
3 dsa 2000 20
3 dsa 2000 20
2 bca 1050 10
1 abc 1000 10
I have a query
WITH dept_count AS (
SELECT
e.*,
dense_rank() over( ORDER BY salary DESC) AS rk
FROM employees e
)
SELECT
*
FROM dept_count dc
WHERE dc.rk BETWEEN (
SELECT
c.rk-2
FROM dept_count c
WHERE c.rk =4
)
AND (
SELECT
c.rk + 2
FROM dept_count c
WHERE c.rk = 4
)
but I need a query which can be simplified.
Could someone help me with this query?
You just need to use ROW_NUMBER() along with a substitution parameter :
WITH dept_count AS (
SELECT
e.*,
ROW_NUMBER() OVER( ORDER BY salary DESC) AS rk
FROM employees e
)
SELECT *
FROM dept_count
WHERE rk BETWEEN &prm - 2 AND &prm + 2
I had been looking for the query to find the 3rd highest salary from the database (using Oracle database). I found the below query -
SELECT *
FROM
( SELECT e.*, row_number() over (order by sal DESC) rn FROM emp e
)
WHERE rn = 3;
I do not have oracle installed in my system, so I'm not try it out. But I want to know if the below query will work or not. If not, then why ?
WITH Sal_sort AS
(SELECT DISTINCT sal FROM salary ORDER BY sal DESC
)
SELECT * FROM Salary S, Sal_sort SS WHERE S.Sal = SS.Sal AND SS.rownum = 3;
Input Data
emp_no emp_fname emp_lname salary
1 aa bb 30
2 ee yy 31
3 rr uu 32
4 tt ii 33
5 tt ii 33
6 tt ii 33
7 tt ii 33
8 tt ii 30
9 tt ii 31
Example:
select * from ee;
select emp_no,salary ,dense_rank() over (order by salary ) dr
from ee
Output
emp_no salary dr
1 30 1
8 30 1
9 31 2
2 31 2
3 32 3
4 33 4
5 33 4
6 33 4
7 33 4
So much easier in version 12 of the database and higher now.
SELECT *
FROM employees
ORDER BY salary DESC OFFSET 2 ROWS FETCH NEXT 1 ROWS ONLY
Tim talks about this feature here.
And if you take a look at the plan, you can see it's not magic, the optimizer is using analytic functions to derive the results.
JUST ONE LINE
select * from (
select salary,dense_rank() over (order by salary desc) rank from employees) where rank=3;
or
select * from (
select a.*,dense_rank() over (order by a.salary desc) rank from employees a) where rank=3;
Without Dense_rank()
SELECT salary FROM employees
ORDER BY salary DESC
OFFSET 2
FETCH 1 NEXT ONE ROWS ONLY;
With Dense_rank()
SELECT salary
FROM
(
SELECT salary, DENSE_RANK() OVER (ORDER BY salary DESC) as rank from employees
)
WHERE rank = 3;