I tried to search posts, but I only found solutions for SQL Server/Access. I need a solution in MySQL (5.X).
I have a table (called history) with 3 columns: hostid, itemname, itemvalue.
If I do a select (select * from history), it will return
+--------+----------+-----------+
| hostid | itemname | itemvalue |
+--------+----------+-----------+
| 1 | A | 10 |
+--------+----------+-----------+
| 1 | B | 3 |
+--------+----------+-----------+
| 2 | A | 9 |
+--------+----------+-----------+
| 2 | C | 40 |
+--------+----------+-----------+
How do I query the database to return something like
+--------+------+-----+-----+
| hostid | A | B | C |
+--------+------+-----+-----+
| 1 | 10 | 3 | 0 |
+--------+------+-----+-----+
| 2 | 9 | 0 | 40 |
+--------+------+-----+-----+
I'm going to add a somewhat longer and more detailed explanation of the steps to take to solve this problem. I apologize if it's too long.
I'll start out with the base you've given and use it to define a couple of terms that I'll use for the rest of this post. This will be the base table:
select * from history;
+--------+----------+-----------+
| hostid | itemname | itemvalue |
+--------+----------+-----------+
| 1 | A | 10 |
| 1 | B | 3 |
| 2 | A | 9 |
| 2 | C | 40 |
+--------+----------+-----------+
This will be our goal, the pretty pivot table:
select * from history_itemvalue_pivot;
+--------+------+------+------+
| hostid | A | B | C |
+--------+------+------+------+
| 1 | 10 | 3 | 0 |
| 2 | 9 | 0 | 40 |
+--------+------+------+------+
Values in the history.hostid column will become y-values in the pivot table. Values in the history.itemname column will become x-values (for obvious reasons).
When I have to solve the problem of creating a pivot table, I tackle it using a three-step process (with an optional fourth step):
select the columns of interest, i.e. y-values and x-values
extend the base table with extra columns -- one for each x-value
group and aggregate the extended table -- one group for each y-value
(optional) prettify the aggregated table
Let's apply these steps to your problem and see what we get:
Step 1: select columns of interest. In the desired result, hostid provides the y-values and itemname provides the x-values.
Step 2: extend the base table with extra columns. We typically need one column per x-value. Recall that our x-value column is itemname:
create view history_extended as (
select
history.*,
case when itemname = "A" then itemvalue end as A,
case when itemname = "B" then itemvalue end as B,
case when itemname = "C" then itemvalue end as C
from history
);
select * from history_extended;
+--------+----------+-----------+------+------+------+
| hostid | itemname | itemvalue | A | B | C |
+--------+----------+-----------+------+------+------+
| 1 | A | 10 | 10 | NULL | NULL |
| 1 | B | 3 | NULL | 3 | NULL |
| 2 | A | 9 | 9 | NULL | NULL |
| 2 | C | 40 | NULL | NULL | 40 |
+--------+----------+-----------+------+------+------+
Note that we didn't change the number of rows -- we just added extra columns. Also note the pattern of NULLs -- a row with itemname = "A" has a non-null value for new column A, and null values for the other new columns.
Step 3: group and aggregate the extended table. We need to group by hostid, since it provides the y-values:
create view history_itemvalue_pivot as (
select
hostid,
sum(A) as A,
sum(B) as B,
sum(C) as C
from history_extended
group by hostid
);
select * from history_itemvalue_pivot;
+--------+------+------+------+
| hostid | A | B | C |
+--------+------+------+------+
| 1 | 10 | 3 | NULL |
| 2 | 9 | NULL | 40 |
+--------+------+------+------+
(Note that we now have one row per y-value.) Okay, we're almost there! We just need to get rid of those ugly NULLs.
Step 4: prettify. We're just going to replace any null values with zeroes so the result set is nicer to look at:
create view history_itemvalue_pivot_pretty as (
select
hostid,
coalesce(A, 0) as A,
coalesce(B, 0) as B,
coalesce(C, 0) as C
from history_itemvalue_pivot
);
select * from history_itemvalue_pivot_pretty;
+--------+------+------+------+
| hostid | A | B | C |
+--------+------+------+------+
| 1 | 10 | 3 | 0 |
| 2 | 9 | 0 | 40 |
+--------+------+------+------+
And we're done -- we've built a nice, pretty pivot table using MySQL.
Considerations when applying this procedure:
what value to use in the extra columns. I used itemvalue in this example
what "neutral" value to use in the extra columns. I used NULL, but it could also be 0 or "", depending on your exact situation
what aggregate function to use when grouping. I used sum, but count and max are also often used (max is often used when building one-row "objects" that had been spread across many rows)
using multiple columns for y-values. This solution isn't limited to using a single column for the y-values -- just plug the extra columns into the group by clause (and don't forget to select them)
Known limitations:
this solution doesn't allow n columns in the pivot table -- each pivot column needs to be manually added when extending the base table. So for 5 or 10 x-values, this solution is nice. For 100, not so nice. There are some solutions with stored procedures generating a query, but they're ugly and difficult to get right. I currently don't know of a good way to solve this problem when the pivot table needs to have lots of columns.
SELECT
hostid,
sum( if( itemname = 'A', itemvalue, 0 ) ) AS A,
sum( if( itemname = 'B', itemvalue, 0 ) ) AS B,
sum( if( itemname = 'C', itemvalue, 0 ) ) AS C
FROM
bob
GROUP BY
hostid;
Another option,especially useful if you have many items you need to pivot is to let mysql build the query for you:
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'ifnull(SUM(case when itemname = ''',
itemname,
''' then itemvalue end),0) AS `',
itemname, '`'
)
) INTO #sql
FROM
history;
SET #sql = CONCAT('SELECT hostid, ', #sql, '
FROM history
GROUP BY hostid');
PREPARE stmt FROM #sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
FIDDLE
Added some extra values to see it working
GROUP_CONCAT has a default value of 1000 so if you have a really big query change this parameter before running it
SET SESSION group_concat_max_len = 1000000;
Test:
DROP TABLE IF EXISTS history;
CREATE TABLE history
(hostid INT,
itemname VARCHAR(5),
itemvalue INT);
INSERT INTO history VALUES(1,'A',10),(1,'B',3),(2,'A',9),
(2,'C',40),(2,'D',5),
(3,'A',14),(3,'B',67),(3,'D',8);
hostid A B C D
1 10 3 0 0
2 9 0 40 5
3 14 67 0 8
Taking advantage of Matt Fenwick's idea that helped me to solve the problem (a lot of thanks), let's reduce it to only one query:
select
history.*,
coalesce(sum(case when itemname = "A" then itemvalue end), 0) as A,
coalesce(sum(case when itemname = "B" then itemvalue end), 0) as B,
coalesce(sum(case when itemname = "C" then itemvalue end), 0) as C
from history
group by hostid
I edit Agung Sagita's answer from subquery to join.
I'm not sure about how much difference between this 2 way, but just for another reference.
SELECT hostid, T2.VALUE AS A, T3.VALUE AS B, T4.VALUE AS C
FROM TableTest AS T1
LEFT JOIN TableTest T2 ON T2.hostid=T1.hostid AND T2.ITEMNAME='A'
LEFT JOIN TableTest T3 ON T3.hostid=T1.hostid AND T3.ITEMNAME='B'
LEFT JOIN TableTest T4 ON T4.hostid=T1.hostid AND T4.ITEMNAME='C'
use subquery
SELECT hostid,
(SELECT VALUE FROM TableTest WHERE ITEMNAME='A' AND hostid = t1.hostid) AS A,
(SELECT VALUE FROM TableTest WHERE ITEMNAME='B' AND hostid = t1.hostid) AS B,
(SELECT VALUE FROM TableTest WHERE ITEMNAME='C' AND hostid = t1.hostid) AS C
FROM TableTest AS T1
GROUP BY hostid
but it will be a problem if sub query resulting more than a row, use further aggregate function in the subquery
If you could use MariaDB there is a very very easy solution.
Since MariaDB-10.02 there has been added a new storage engine called CONNECT that can help us to convert the results of another query or table into a pivot table, just like what you want:
You can have a look at the docs.
First of all install the connect storage engine.
Now the pivot column of our table is itemname and the data for each item is located in itemvalue column, so we can have the result pivot table using this query:
create table pivot_table
engine=connect table_type=pivot tabname=history
option_list='PivotCol=itemname,FncCol=itemvalue';
Now we can select what we want from the pivot_table:
select * from pivot_table
More details here
My solution :
select h.hostid, sum(ifnull(h.A,0)) as A, sum(ifnull(h.B,0)) as B, sum(ifnull(h.C,0)) as C from (
select
hostid,
case when itemName = 'A' then itemvalue end as A,
case when itemName = 'B' then itemvalue end as B,
case when itemName = 'C' then itemvalue end as C
from history
) h group by hostid
It produces the expected results in the submitted case.
I make that into Group By hostId then it will show only first row with values,
like:
A B C
1 10
2 3
I figure out one way to make my reports converting rows to columns almost dynamic using simple querys. You can see and test it online here.
The number of columns of query is fixed but the values are dynamic and based on values of rows. You can build it So, I use one query to build the table header and another one to see the values:
SELECT distinct concat('<th>',itemname,'</th>') as column_name_table_header FROM history order by 1;
SELECT
hostid
,(case when itemname = (select distinct itemname from history a order by 1 limit 0,1) then itemvalue else '' end) as col1
,(case when itemname = (select distinct itemname from history a order by 1 limit 1,1) then itemvalue else '' end) as col2
,(case when itemname = (select distinct itemname from history a order by 1 limit 2,1) then itemvalue else '' end) as col3
,(case when itemname = (select distinct itemname from history a order by 1 limit 3,1) then itemvalue else '' end) as col4
FROM history order by 1;
You can summarize it, too:
SELECT
hostid
,sum(case when itemname = (select distinct itemname from history a order by 1 limit 0,1) then itemvalue end) as A
,sum(case when itemname = (select distinct itemname from history a order by 1 limit 1,1) then itemvalue end) as B
,sum(case when itemname = (select distinct itemname from history a order by 1 limit 2,1) then itemvalue end) as C
FROM history group by hostid order by 1;
+--------+------+------+------+
| hostid | A | B | C |
+--------+------+------+------+
| 1 | 10 | 3 | NULL |
| 2 | 9 | NULL | 40 |
+--------+------+------+------+
Results of RexTester:
http://rextester.com/ZSWKS28923
For one real example of use, this report bellow show in columns the hours of departures arrivals of boat/bus with a visual schedule. You will see one additional column not used at the last col without confuse the visualization:
** ticketing system to of sell ticket online and presential
This isn't the exact answer you are looking for but it was a solution that i needed on my project and hope this helps someone. This will list 1 to n row items separated by commas. Group_Concat makes this possible in MySQL.
select
cemetery.cemetery_id as "Cemetery_ID",
GROUP_CONCAT(distinct(names.name)) as "Cemetery_Name",
cemetery.latitude as Latitude,
cemetery.longitude as Longitude,
c.Contact_Info,
d.Direction_Type,
d.Directions
from cemetery
left join cemetery_names on cemetery.cemetery_id = cemetery_names.cemetery_id
left join names on cemetery_names.name_id = names.name_id
left join cemetery_contact on cemetery.cemetery_id = cemetery_contact.cemetery_id
left join
(
select
cemetery_contact.cemetery_id as cID,
group_concat(contacts.name, char(32), phone.number) as Contact_Info
from cemetery_contact
left join contacts on cemetery_contact.contact_id = contacts.contact_id
left join phone on cemetery_contact.contact_id = phone.contact_id
group by cID
)
as c on c.cID = cemetery.cemetery_id
left join
(
select
cemetery_id as dID,
group_concat(direction_type.direction_type) as Direction_Type,
group_concat(directions.value , char(13), char(9)) as Directions
from directions
left join direction_type on directions.type = direction_type.direction_type_id
group by dID
)
as d on d.dID = cemetery.cemetery_id
group by Cemetery_ID
This cemetery has two common names so the names are listed in different rows connected by a single id but two name ids and the query produces something like this
CemeteryID Cemetery_Name Latitude
1 Appleton,Sulpher Springs 35.4276242832293
You can use a couple of LEFT JOINs. Kindly use this code
SELECT t.hostid,
COALESCE(t1.itemvalue, 0) A,
COALESCE(t2.itemvalue, 0) B,
COALESCE(t3.itemvalue, 0) C
FROM history t
LEFT JOIN history t1
ON t1.hostid = t.hostid
AND t1.itemname = 'A'
LEFT JOIN history t2
ON t2.hostid = t.hostid
AND t2.itemname = 'B'
LEFT JOIN history t3
ON t3.hostid = t.hostid
AND t3.itemname = 'C'
GROUP BY t.hostid
I'm sorry to say this and maybe I'm not solving your problem exactly but PostgreSQL is 10 years older than MySQL and is extremely advanced compared to MySQL and there's many ways to achieve this easily. Install PostgreSQL and execute this query
CREATE EXTENSION tablefunc;
then voila! And here's extensive documentation: PostgreSQL: Documentation: 9.1: tablefunc or this query
CREATE EXTENSION hstore;
then again voila! PostgreSQL: Documentation: 9.0: hstore
I have to reach the best performance!
So, i have a table (my_table1) where are 3 columns: ID, RID(primary_key), VALUE1.
I want to make a new boolean column in another table (my_table2).
I decode-d my VALUE1 column, so its output can be 1 or NULL.
RID | ID | VALUE1
--------|--------|--------
132501 | 1001 | 1
132501 | 1002 |
132501 | 1003 |
132501 | 1004 | 1
132501 | 1005 |
132501 | 1006 | 1
If all values of VALUE1 column is 1 i want to get 1.
If ANY value of VALUE1 column is NULL i want to get 0.
In this specific case output be like - (my_table2):
RID_2 |ID_TBL_2| NEW_BOOL_COL
--------|--------|--------
132501 | 3214 | 0
What's the best way to solve this problem ?
Here is an answer which aggregates VALUE1 based on the RID:
SELECT
RID,
CASE WHEN COUNT(VALUE1) = COUNT(*) THEN 1 ELSE 0 END AS NEW_BOOL_COL
FROM my_table1
GROUP BY RID;
You may easily enough use this logic in the context of joining to another table.
There's no boolean column type for tables in Oracle. I think you're looking for an Integer.
You may use a correlated update with a count query from my_table1
update my_table2 t2 set NEW_BOOL_COL =
( select
case when count( case when value1 = 1 then 1 end ) =
count(*) then 1 else 0 end
from my_table1 t1 where t1.rid = t2.rid_2
group by t1.rid
);
DEMO
I am working on a complex sql query. Just for explaning purpose of my issue i have reduced to the below short query:
select a.column1 as field1,b.column2 as field 2,c.column3 as field3,COALESCE(SUM(d.paid_amt) OVER (PARTITION BY a.some_column),0) as amount_paid
from a Inner join b on b.column3=ac.olumn2
right join c on c.column4=b.column1
left join d on d.column2=a.column1 and d.column5 = a.column1
where ...//some conditions
SO i am quite sure whats happening here. I am more concerned on the last left join on d table. if the d table has no records which matches d.column5 = a.column1 then i am not getting any results.
But i am trying to write the query in such a way that if d table retuns any values with the where condition d.column5 = a.column1 then i want to use those values or else if there are no records in d table i just want to get the records from the result of previous joins and get the records that i need.
Here with the current query the problem is as expected, if the join doesnt match the where condition its eliminating all the records. I want to have the records no matter what if the where condition satisfies or not.
I am not quite sure how to do this in one single query. Any suggestions are appreciated.
Note: #scaisEdge and #Zaynul Answer works fine. but the problem is the amount caluclation if i move the condition in line on join and clause. The am ount calculation should also be on the same condition d.column5 = a.column1.So i am not really sure how to overcome this :(
Sample date below:
field1 | field2 | field3 | ampount_paid | some_column_to_match
--------------------------------------------------------------
name | value1 | other1 | 100 | 1
name1 | value2 | other2 | 100 | 1
name2 | value3 | other3 | 100 | 2
So i have just added the last columns to explain how i want the sum. I want sum the fields only if the some_column_to_match matches. So i am trying to get the output like:
field1 | field2 | field3 | amount_paid | some_column_to_match
--------------------------------------------------------------
name | value1 | other1 | 200 | 1
name1 | value2 | other2 | 200 | 1
name2 | value3 | other3 | 100 | 2
So basically the calculation should be the sum of all values in amount_paid where some_column_to_match value matches. So in the above example, the first two columns should return 200 as it as 100 in each individual field for the same value.
If you want a left join then you should not use columns of left joined table (d.column5 = a.column1) in where condition in this way the join became an inner join
In these case add the condition for the columns related to the left join table at the corresponding ON clase
select a.column1
,b.column2
,c.column3
,d.column4
from a Inner join b on b.column3=ac.olumn2
right join c on c.column4=b.column1
left join d on d.column2=a.column1 AND d.column5 = a.column1
Given a table with a (non-distinct) identifier and a value:
| ID | Value |
|----|-------|
| 1 | A |
| 1 | B |
| 1 | C |
| 1 | D |
| 2 | A |
| 2 | B |
| 2 | C |
| 3 | A |
| 3 | B |
How can you select the grouped identifiers, which have values for a given list? (e.g. ('B', 'C'))
This list might also be the result of another query (like SELECT Value from Table1 WHERE ID = '2' to find all IDs which have a superset of values, compared to ID=2 (only ID=1 in this example))
Result
| ID |
|----|
| 1 |
| 2 |
1 and 2 are part of the result, as they have both A and B in their Value-column. 3 is not included, as it is missing C
Thanks to the answer from this question: SQL Select only rows where exact multiple relationships exist I created a query which works for a fixed list. However I need to be able to use the results of another query without changing the query. (And also requires the Access-specific IFF function):
SELECT ID FROM Table1
GROUP BY ID
HAVING SUM(Value NOT IN ('A', 'B')) = 0
AND SUM(IIF(Value='A', 1, 0)) = 1
AND SUM(IIF(Value='B', 1, 0)) = 1
In case it matters: The SQL is run on a Excel-table via VBA and ADODB.
In the where criteria filter on the list of values you would like to see, group by id and in the having clause filter on those ids which have 3 matching rows.
select id from table1
where value in ('A', 'B', 'C') --you can use a result of another query here
group by id
having count(*)=3
If you can have the same id - value pair more than once, then you need to slightly alter the having clause: having count(distinct value)=3
If you want to make it completely dynamic based on a subquery, then:
select id, min(valcount) as minvalcount from table1
cross join (select count(*) as valcount from table1 where id=2) as t1
where value in (select value from table1 where id=2) --you can use a result of another query here
group by id
having count(*)=minvalcount
What is the most clever way to delete tuples from table1, that are in the second table,
if the second table is not a part of initial database, but a result of some really big query?
table1 *this table is a result of some query
------------- -------------
| id1 | id2 | | id1 | id2 |
------------- -------------
| 1 2 | | 5 6 |
| 3 4 | | 1 2 |
| 5 6 | | 11 12 |
| 7 8 | -------------
| 9 10 |
| 11 12 |
| 13 14 |
-------------
I came up with
delete from table1
where id1 in (select id1 from ( really long query to get a second table))
and id2 in (select id2 from (the same really long query to get a second table));
It works, but I feel like I'm doing it way too wrong, and not keeping the query DRY.
And would the way you suggest work the same if table1 had an additional column, for example "somecol"?
IMO, You can use EXISTS statement like this:
DELETE FROM table1
WHERE EXISTS (
SELECT 1
FROM (<your long query>) AS dt
WHERE table1.id1 = dt.id1
AND table1.id2 = dt.id2);
[SQL Fiddle Sample]
One method is to use with, delete and exists:
with secondtable as (
<your query here>
)
delete from table1
where exists (select 1
from secondtable st
where table1.id1 = st.id1 and table1.id2 = st.id2
);
A Correlated Subquery using EXISTS allows matching multiple columns:
delete
from table1
where exists
( select * from
(
"really long query"
) as t2
where table1.id1 = t2.id1 -- correlating inner and outer table
and table1.id2 = t2.id2 -- similar to a join-condition
)