Let's assume I have a table A:
| ID | B_ID | C | column 1 | ... | column x|
| 1 | 24 | 44 | xxxxxxx
| 2 | 25 | 55 | xxxxxxx
| 3 | 25 | 66 | xxxxxxx (data in all other columns are the same)
| 4 | 26 | 77 | xxxxxxx
| 4 | 26 | 78 | xxxxxxx
| 4 | 26 | 79 | xxxxxxx
I want to get highest number of distinct records with same B_ID (and I also want to know B_ID where this occurs). So in this example I want to get values 3 and 26.
What would be best approach to achieve this?
The best approach is a simple aggregation + ordering + limiting the number of rows returned to 1:
select b_id, no_of_records
from (
select b_id, count(1) as no_of_records
from table_A
group by b_id
order by no_of_records desc
)
where rownum <= 1;
This, of course, returns 1 row even if you have multiple groups with the same highest number of records. If you want all groups with the same highest number of records, then the approach is slightly different ...
select b_id, no_of_records
from (
select b_id, count(1) as no_of_records,
rank() over (partition by null order by count(1) desc) as rank$
from table_A
group by b_id
)
where rank$ <= 1;
Related
I have hierarchical data as follows.
|Serial No | Primary Flag |Prev SerialNo|
| 101 | 1 | 56 |
| 56 | 0 | NULL |
| 505 | 0 | NULL |
| 223 | 1 | 156 |
| 156 | 0 | 93 |
| 93 | 0 | 42 |
42 | 0 | NULL |
First two rows are related by Previous serial number when primary flag, so total counts in their hierarchy is 2
Third row is not related to any thing since Previous serial number is NULL., so total count is 0.
Fourth row is related to below 3 records, so total count is 4.
I need a query to find the total related counts for rows when Primary flag is 1.How can I achieve this in Teradata?
Assuming you don't want to return a row for Serial_No 505, you can use a recursive query and aggregation:
WITH RECURSIVE r AS (
SELECT h.Serial_No AS Primary_SerialNo, h.Serial_No, h.Prev_SerialNo, 1 (INTEGER) as Level
FROM hierTbl h WHERE h.Primary_Flag=1
UNION ALL
SELECT r.Primary_SerialNo, h.Serial_No, h.Prev_SerialNo, r.Level+1
FROM hierTbl h JOIN r ON r.Prev_SerialNo = h.Serial_No
)
Select Primary_SerialNo, MAX(Level) as Related
FROM r GROUP BY 1;
Let's say I have a table:
+--------------+--------------+------+-----+
| ID | Score | email | add |
+--------------+--------------+------+-----+
| 123 | 88 | 123#gmail.com | somewhere |
| 456 | 77 | 123#gmail.com | somewhere |
| 789 | 88 | 123#gmail.com | somewhere |
| 111 | 77 |123#gmail.com | somewhere |
| 555 | 77 | 123#gmail.com | somewhere |
|444 | 88 | 123#gmail.com | somewhere
| 222 | 77 | 123#gmail.com | somewhere |
| 333 | 88 |123#gmail.com | somewhere |
My question is it possible to select Score column and ONLY print out first 3 88 and 77 Score?
I tried but it seems only give me 3 88 scores only
SELECT Score
FROM Table_Name
WHERE Score = '88' OR Score = '77'
LIMIT 3
First filter the table so that only the rows with the scores that you want are returned and then use ROW_NUMBER() window function to rank the rows of each Score based on ID so that you can filter out the rows that exceed the first 3 of each group:
SELECT ID, Score, email, add
FROM (
SELECT *, ROW_NUMBER() OVER (PARTITION BY Score ORDER BY ID) rn
FROM Table_Name
WHERE Score = '88' OR Score = '77'
)
WHERE rn <= 3;
For versions of SQLite prior to 3.25.0 that do not support window functions use a correlated subquery:
SELECT t1.*
FROM Table_Name t1
WHERE t1.Score = '88' OR t1.Score = '77'
AND (SELECT COUNT(*) FROM Table_Name t2 WHERE t2.Score = t1.Score AND t2.ID <= t1.ID) <= 3;
I want to get 1 entry per day per hour from my MariaDB database.
I have a table structured like this (with some more columns):
+------------+-----------+
| dayOfMonth | hourOfDay |
+------------+-----------+
Let's assume this table is filled like this:
+------------+-----------+
| dayOfMonth | hourOfDay |
+------------+-----------+
| 11 | 0 |
| 11 | 0 |
| 11 | 1 |
| 12 | 0 |
| 12 | 0 |
| 12 | 1 |
+------------+-----------+
What I want to get is this(in fact all columns) (Every hourOfDay for each dayOfMonth):
+------------+-----------+
| dayOfMonth | hourOfDay |
+------------+-----------+
| 11 | 0 |
| 11 | 1 |
| 12 | 0 |
| 12 | 1 |
+------------+-----------+
I was able to achieve this with this statement, but it would become way too long if I want to do this for an entire month:
(SELECT * FROM table WHERE dayOfMonth = 11 GROUP BY hourOfDay)
UNION
(SELECT * FROM table WHERE dayOfMonth = 12 GROUP BY hourOfDay)
You can group by dayOfMonth, hourOfDay:
SELECT dayOfMonth, hourOfDay
FROM table
GROUP BY dayOfMonth, hourOfDay
ORDER BY dayOfMonth, hourOfDay
This way you can't select other columns (if they exist), only aggregate on them with MIN(), MAX(), AVG() etc.
Or use DISTINCT:
SELECT DISTINCT dayOfMonth, hourOfDay
FROM table
ORDER BY dayOfMonth, hourOfDay
Your question is unclear. This will transform your initial data into your proposed data:
SELECT DISTINCT
dayOfMonth, hourOfDay
FROM tbl;
"Every hourOfDay" -- do you want all hours 24 rows per day? Of so, see the "sequence table" (eg, seq_0_to_23) feature in MariaDB.
I have an SQLite table similar to the following:
| A | B |
_________
| e | 5 |
| f | 7 |
| a | 5 |
| n | 7 |
| g | 5 |
| d | 7 |
| i | 5 |
| j | 5 |
| e | 7 |
| v | 7 |
How can I retrieve three random rows with value 5 in column B and three random rows with value 7? I don't know values in B, neither values5 ad 7. I want 3 random rows for each different value in B. Result may be not grouped by column B values. It could be something like:
| A | B |
_________
| e | 5 |
| g | 5 |
| e | 7 |
| v | 7 |
| j | 5 |
| f | 7 |
The following almost does what you want:
select t.*
from t
where t.rowid in (select t2.rowid
from t t2
where t2.b = t.b
order by random()
limit 3
);
Alas, the subquery will be run for every row, so this is only approximate because the random number generator changes values on each execution.
One solution is to use a temporary table to store a random number for each row, which can then be used for sorting. Unfortunately, a CTE doesn't seem to do the trick, because these are re-evaluated on each reference.
After some thought, I think a temporary table might be the only solution:
drop table if exists tempt;
create temporary table tempt as
select t.*, random() as rand
from t;
select t.*
from tempt t
where t.rowid in (select t2.rowid
from tempt t2
where t2.b = t.b
order by rand
limit 3
);
You can use the hidden RowID column to get three rows per B value as follows:
SELECT A, B FROM T T1
WHERE RowID IN (SELECT RowID FROM T T2 WHERE B = T1.B LIMIT 3);
Note that you're likely (but not 100% guaranteed) to get the same three rows each time. If you want to get random rows at the expense of some performance, you can do:
SELECT A, B FROM T T1
WHERE RowID IN (SELECT RowID FROM T T2 WHERE B = T1.B ORDER BY random() LIMIT 3);
I have the following table in an sqlite database
+----+-------------+-------+
| ID | Week Number | Count |
+----+-------------+-------+
| 1 | 1 | 31 |
| 2 | 2 | 16 |
| 3 | 3 | 73 |
| 4 | 4 | 59 |
| 5 | 5 | 44 |
| 6 | 6 | 73 |
+----+-------------+-------+
I want to get the following table out. Where I get this weeks sales as one column and then the next column will be last weeks sales.
+-------------+-----------+-----------+
| Week Number | This_Week | Last_Week |
+-------------+-----------+-----------+
| 1 | 31 | null |
| 2 | 16 | 31 |
| 3 | 73 | 16 |
| 4 | 59 | 73 |
| 5 | 44 | 59 |
| 6 | 73 | 44 |
+-------------+-----------+-----------+
This is the select statement i was going to use:
select
id, week_number, count,
(select count from tempTable
where week_number = (week_number-1))
from
tempTable;
You are comparing values in two different rows. When you are just writing week_number, the database does not know which one you mean.
To refer to a column in a specific table, you have to prefix it with the table name: tempTable.week_number.
And if both tables have the same name, you have to rename at least one of them:
SELECT id,
week_number,
count AS This_Week,
(SELECT count
FROM tempTable AS T2
WHERE T2.week_number = tempTable.week_number - 1
) AS Last_Week
FROM tempTable;
In case of you want to take a query upon a same table twice, you have to put aliases on the original one and its replicated one to differentiate them
select a.week_number,a.count this_week,
(select b.count from tempTable b
where b.week_number=(a.week_number-1)) last_week
from tempTable a;