i have a table t1. which has the following value.
+----+-----+-----+-----+-----+-----+
| t1 | s1 | s2 | s3 | s4 | s5 |
+----+-----+-----+-----+-----+-----+
| 1 | 0 | 1 | 0 | 0 | 2 |
|----|-----|-----|-----|-----|-----|
| 2 | 1 | 0 | 0 | 1 | 2 |
+----+-----+-----+-----+-----+-----+
how to fetch column name. which has the value 0.
I think, you are trying to get the column/field name which has all the rows 0, or which has all its values as 0. For example: column s3 in your case.
One possible way to get the column is following:
You first find the sum of each column. Now if a column has all its values as 0, sum for this column would be zero. Having done that, you use an " if " condition to return only those column whose sum is 0. You could also use "concat_ws" to comma separated those columns, in case you have more than one. So, here is the query. Also, let me draw the table again. Its a bit confusing the way you have drawn.
You table name is t1. It has five columns s1,s2,s3,s4,s5 and a total of two rows. You look to find s3, which has all its values as 0.
# Table t1 #
s1 s2 s3 s4 s5
0 1 0 0 1
1 0 0 1 0
select concat_ws( ',' , if(sum(s1)=0 , 's1' , null) , if(sum(s2)=0 , 's2' , null) , if(sum(s3)=0, 's3' , null) , if(sum(s4)=0, 's4', null), if(sum(s5)=0, 's5', null) ) as empty_column from t1;
Related
There are two types of data in the same mysql table.
Some data's specific column is set to '1' and another data's column is set to '0' (0 and 1 in the same column)
How can I mix them at once like below? (with select query) - every six '0' row is followed by one '1' row.
Well, you could use window functions for sorting - if you are running MySQL 8.0:
select code, val
from mytable
order by
row_number() over(partition by val order by code)
* (case when val = 0 then 1 else 5 end),
val,
code
The logic is to rank records having the same value ; then simple artithmetics can be used to handle the alternation (5 0s, then 1 1).
Demo on DB Fiddle:
code | val
:----- | --:
data1 | 0
data10 | 0
data11 | 0
data12 | 0
data13 | 0
data2 | 1
data14 | 0
data15 | 0
data3 | 0
data4 | 0
data5 | 0
data8 | 1
data6 | 0
data7 | 0
data9 | 0
I would phrase this as:
order by ( floor(row_number() over (partition by column order by data) - 1) /
(case when column = 1 then 1 else 5 end)
)
),
column,
data
I've tried a few PROCEDURES and LOOPS, but i'm having trouble getting my results.
I have a table of 19,000 records that looks like this:
id | seq | custom_id
1 | 0 | 123
2 | 0 | 124
3 | 1 | NULL
4 | 0 | 125
5 | 1 | NULL
6 | 2 | NULL
7 | 3 | NULL
My goal is:
id | seq | custom_id
1 | 0 | 123
2 | 0 | 124
3 | 1 | 124-1
4 | 0 | 125
5 | 1 | 125-1
6 | 2 | 125-2
7 | 3 | 125-3
So if seq is 0 it will have a custom ID. if seq is not 0 I would like to get the custom id and concat -seq to the end.
In a Correlated Subquery, we can get the previous (and closest) custom_id value where the seq is 0.
Now, we simply need to use Concat() function to concatenate the previous custom_id value with the current row's seq value, to get the new custom_id.
Try the following query to Select the data (DB Fiddle DEMO):
SELECT
t1.id,
t1.seq,
CASE WHEN t1.seq = 0 THEN t1.custom_id
ELSE CONCAT((SELECT t2.custom_id
FROM your_table AS t2
WHERE t2.id < t1.id AND
t2.seq = 0
ORDER BY t2.id DESC LIMIT 1), '-', t1.seq)
END AS custom_id
FROM your_table AS t1
However, based on your comments, it seems that you are interested in Updating the custom_id column at once. In MySQL, using subquery on the same table (which is being updated as well), is possible via Derived Tables approach.
We determine the modified custom_id for id where seq <> 0 in a sub-select result set (Derived table), and then Join it back to the main table for update.
Try the following for Updating the data (DB Fiddle DEMO):
UPDATE
your_table AS tab
JOIN
(
SELECT
t1.id,
CONCAT((SELECT t2.custom_id
FROM your_table AS t2
WHERE t2.id < t1.id AND
t2.seq = 0
ORDER BY t2.id DESC LIMIT 1),
'-', t1.seq) AS custom_id
FROM your_table AS t1
WHERE t1.seq <> 0
) AS dtab ON dtab.id = tab.id
SET tab.custom_id = dtab.custom_id
WHERE tab.seq <> 0;
I have a table where I store data for different groups and I need to update one group if values in one column are matching.
the table looks like this:
prop_id | group_id | value | visible
1 | 1 | 10 | 1
1 | 2 | 10 | 1
1 | 3 | 15 | 1
2 | 1 | 10 | 1
2 | 2 | 10 | 1
2 | 3 | 10 | 1
So I want to set the visible column to 0 for the group_id=3 if the values in the value column are equal to group_id=1. In this case if value=10 for both group_id=1 and group_id=3 than set visible=0 for group_id=3
expected result after update
prop_id | group_id | value | visible
1 | 1 | 10 | 1
1 | 2 | 10 | 1
1 | 3 | 15 | 1
2 | 1 | 10 | 1
2 | 2 | 10 | 1
2 | 3 | 10 | 0
How is this possible?
Write it as a SELECT first.
Start simple, the rows that we want to update we know are group_id=3 and visible=1, so write a query that gets all of those rows:
SELECT g3.value
, g3.visible
FROM mytable g3
WHERE g3.group_id = 3
AND g3.visible = 1
We know the rows we want to update are in that set, but there are some additional conditions.
So we extend that. According to the spec, we need to find out if there are any matching group_id=1 rows that are visible=1 (matching on value).
We can do that check either with an EXISTS correlated subquery, or we can use a JOIN.
SELECT g3.group_id
, g3.value
, g3.visible
FROM mytable g3
WHERE g3.group_id = 3
AND g3.visible = 1
AND EXISTS ( SELECT 1
FROM mytable g1
WHERE g1.group_id = 1
AND g1.visible = 1
AND g1.value = g3.value
)
-or-
SELECT g3.group_id
, g3.value
, g3.visible
FROM mytable g3
JOIN mytable g1
ON g1.group_id = 1
AND g1.visible = 1
AND g1.value = g3.value
WHERE g3.group_id = 3
AND g3.visible = 1
Verify the query is returning the rows we want to update, under the specific conditions. (It is much easier to verify the results of a SELECT statement, and adjust as necessary, than it is an UPDATE statement.)
Once we have a SELECT query working and verified (returning the rows we want to update) we can convert it into an UPDATE statement. Replace the SELECT ... FROM with UPDATE and add a SET clause that is returning the rows
UPDATE mytable g3
JOIN mytable g1
ON g1.group_id = 1
AND g1.visible = 1
AND g1.value = g3.value
SET g3.visible = 0
WHERE g3.group_id = 3
AND g3.visible = 1
Use Self JOIN then UPDATE
You can try this.
UPDATE T t1
JOIN T t2 on t1.group_id = t2.group_id
and t1.rop_id<>t2.rop_id and t1.value > t2.value
SET t2.visible = 0
sqlfiddle:http://sqlfiddle.com/#!9/6f06de/1
So, lets say I have a table called "imports" that looks like this:
| id | importer_id | total_m | total_f |
|====|=============|=========|=========|
| 1 | 1 | 100 | 200 |
| 1 | 1 | 0 | 200 |
And I need the query to return it pivoted or transposed (rows to columns) in this way:
| total_m | sum(total_m) |
| total_f | sum(total_f) |
I can't think on a way to do this without using another table (maybe a temporary table?) and using unions, but there should be a better way to this anyway (maybe with CASE or IF?).
Thanks in advance.
select 'total_m', sum(total_m) from imports
union
select 'total_f', sum(total_f) from imports
http://sqlfiddle.com/#!9/fc1c0/2/0
You can "unpivot" by first expanding the number of rows, which is done below by cross joining a 2 row subquery. Then on each of those rows use relevant case expression conditions to align the former columns to the new rows ("conditional aggregates").
SQL Fiddle
MySQL 5.6 Schema Setup:
CREATE TABLE imports
(`id` int, `importer_id` int, `total_m` int, `total_f` int)
;
INSERT INTO imports
(`id`, `importer_id`, `total_m`, `total_f`)
VALUES
(1, 1, 100, 200),
(1, 1, 0, 200)
;
Query 1:
select
*
from (
select
i.importer_id
, concat('total_',cj.unpiv) total_type
, sum(case when cj.unpiv = 'm' then total_m
when cj.unpiv = 'f' then total_f else 0 end) as total
from imports i
cross join (select 'm' as unpiv union all select 'f') cj
group by
i.importer_id
, cj.unpiv
) d
Results:
| importer_id | total_type | total |
|-------------|------------|-------|
| 1 | total_f | 400 |
| 1 | total_m | 100 |
i would like construct a query to count the number of student who don't have number 0.
assuming i have 2 tables
students
*student_id
*name
Number
*number_id
*student_id
*number
| Student 1 |
1
1
1
1
| Student 2 |
1
1
1
1
| Student 3 |
1
0
1
0
|Student 4 |
0
1
1
1
So the result should be. student without zero = 2
student with zero = 2
This answer assumes that your table has the following structure:
id | value
1 | 1
1 | 1
1 | 1
1 | 1
2 | 1
etc...
SELECT id
FROM yourTable
GROUP BY id
HAVING SUM(CASE WHEN value = 0 THEN 1 ELSE 0 END) = 0
Something like this might return the specified result:
SELECT CONCAT('student without zero = '
, ( SELECT SUM(1)
FROM ( SELECT t.`some_identifier`
FROM `sometable` t
GROUP BY t.`some_identifier`
HAVING SUM(IF(t.`some_col`=0,1,0)) = 0
)
)
, '\n'
, 'student with zero = '
, ( SELECT SUM(1)
FROM ( SELECT z.`some_identifier`
FROM `sometable` z
WHERE z.`some_col` = 0
GROUP BY z.`some_identifier`
)
)
) AS `result`
Just replace some_table with the name of the table, some_col with the name of the column that contains the 1 and 0 values, and some_identifier with the column that contains the Student 1, Student 2, etc. values.
This should return a single row, something like this:
result
--------------------------------
student without zero = 2
student with zero = 2