I executed code below.
select expand(both()) from data
where value = '123456'
There are two nodes (node_A, node_B) whose value equals '123456'
and both of them connected with node_C and node_D.
Finally it returned node_C and node_D for several times
but I just want each of them for one time.
I tried to use distinct() around "expand(both())" but failed.
How can I distinct dupulicate nodes?
select expand(distinct(#rid)) from (select expand(both()) from data
where value = '123456')
Related
I am quite new in working with psql.
Goal is to get values from a nested jsonb-structure where the last key has so many different characteristics it is not possible to query them explicitely.
The jsonb-structure in any row is as follows:
TABLE_Products
{'products':[{'product1':['TYPE'], 'product2':['TYPE2','TYPE3'], 'productN':['TYPE_N']}]}
I want to get the values (TYPE1, etc.) assigned to each product-key (product1, etc.). The product-keys are the unknown, because of too many different names.
My work so far achieves to pull out a tuple for each key:value-pair on the last level. To illustrate this here you can see my code and the results from the previously described structure.
My Code:
select url, jsonb_each(pro)
from (
select id , jsonb_array_elements(data #> '{products}') as pro
from TABLE_Products
where data is not null
) z
My result:
("product2","[""TYPE2""]")
("product2","[""TYPE3""]")
My questions:
Is there a way to split this tuple on two columns?
Or how can I query the values kind of 'unsupervised', so without knowing the exact names of 'product1 ... n'
I have PostgreSQL query where I need to return vehicleId, plateNumber and one last "position" data in order to see where the vehicle stopped. I have three tables. Vehicle table, session table storing the sessions and tracking table storing the actual position data of the vehicle.
Getting the plateNumber and vehicleId does work, however adding the position and trying to group the results will end with the following error: ERROR: could not identify an equality operator for type JSON.
Is there any way around this. How could I force (convert the JSON) so it can be actually measured? The JSON contains position data from the mobile which seem to be having a unified structure. There is timestamp, lat, long, speed and heading.
Alternatively is there any other way the query could be written as not to involve the need to compare the JSON data? Any recommendation? I have tried a few different approaches with no result. I always seem to hit the issue with the JSON.
SELECT "plateNumber", "Config.Vehicle"."vehicleId", position
FROM "Config.Vehicle"
INNER JOIN "Config.Session" ON "Config.Session"."vehicleId" = "Config.Vehicle"."vehicleId"
LEFT JOIN (select * from "Config.Tracking" ORDER BY date DESC LIMIT 1) a ON a."sessionId" = "Config.Session"."sessionId"
WHERE "Config.Session"."sessionEnd" IS NOT NULL
GROUP BY 1, 2, 3
I have a UDF in my database which basically tries to get a station (e.g. bus/train) based on some input data (geographic/name/type). Inside this function i try to check if there are any rows matching the given values:
SELECT
COUNT(s.id)
INTO
firsttry
FROM
geographic.stations AS s
WHERE
ST_DWithin(s.the_geom,plocation,0.0017)
AND
s.name <-> pname < 0.8
AND
s.type ~ stype;
The firsttry variable now contains the value 1. If i use the following (slightly extended) SELECT statement i get no results:
RETURN query SELECT
s.id, s.name, s.type, s.the_geom,
similarity(
regexp_replace(s.name::text,'(Hauptbahnhof|Hbf)','Hbf'),
regexp_replace(pname::text,'(Hauptbahnhof|Hbf)','Hbf')
)::double precision AS sml,
st_distance(s.the_geom,plocation) As dist from geographic.stations AS s
WHERE ST_DWithin(s.the_geom,plocation,0.0017) and s.name <-> pname < 0.8
AND s.type ~ stype
ORDER BY dist asc,sml desc LIMIT 1;
the parameters are as follows:
stype = '^railway'
pname = 'Amsterdam Science Park'
plocation = ST_GeomFromEWKT('SRID=4326;POINT(4.9492530 52.3531670)')
the tuple i need to be returned is:
id name type geom (displayed as ST_AsText)
909658;"Amsterdam Sciencepark";"railway_station";"POINT(4.9482893 52.352904)"
The same UDF returns quite well for a lot of other stations, but this is one (of more) which just won't work. Any suggestions?
P.S. The use of the <-> operator is coming from the pg_trgm module.
Some ideas on how to troubleshoot this:
Break your troubleshooting into steps. Start with the simplest query possible. No aggregates, just joins and no filters. Then add filters. Then add order by, then add aggregates. Look at exactly where the change occurs.
Try reindexing the database.
One possibility that occurs to me based on this is that it could be a corrupted index used in the second query but not the first. I have seen corrupted indexes in the past and usually they throw errors but at least in theory they should be able to create a problem like this.
If this is correct, your query will suddenly return rows if you remove the ORDER BY clause.
If you have a corrupted index, then you need to pay close attention to hardware. Is the RAM ECC? Is the processor overheating? How are you disks doing?
A second possibility is that there is a typo on a join condition of filter statement. Normally this is something I would suspect first but it is easy enough to weed out index problems to start there. If removing the ORDER BY doesn't change things, then chances are it is a typo. If you can't find a typo, then try reindexing.
I have a table listing (gameid, playerid, team, max_minions) and I want to get the players within each team that have the lowest max_minions (within each team, within each game). I.e. I want a list (gameid, team, playerid_with_lowest_minions) for each game/team combination.
I tried this:
SELECT * FROM MinionView GROUP BY gameid, team
HAVING MIN(max_minions) = max_minions;
Unfortunately, this doesn't seem to work as it seems to select a random row from the available rows for each (gameid, team) and then does the HAVING comparison. If the randomly selected row doesn't match, it's simply skipped.
Using WHERE won't work either since you can't use aggregate functions within WHERE clauses.
LIMIT won't work since I have many more games and LIMIT limits the total number of rows returned.
Is there any way to do this without adding another table/view that contains (gameid, teamid, MIN(max_minions))?
Example data:
sqlite> SELECT * FROM MinionView;
gameid|playerid|team|champion|max_minions
21|49|100|Champ1|124
21|52|100|Champ2|18
21|53|100|Champ3|303
21|54|200|Champ4|356
21|57|200|Champ5|180
21|58|200|Champ6|21
64|49|100|Champ7|111
64|50|100|Champ8|208
64|53|100|Champ9|8
64|54|200|Champ0|226
64|55|200|ChampA|182
64|58|200|ChampB|15
...
Expected result (I mostly care about playerid, but included champion, max_minions here for better overview):
21|52|100|Champ2|18
21|58|200|Champ6|21
64|53|100|Champ9|8
64|58|200|ChampB|15
...
I'm using Sqlite3 under Python 3.1 if that matters.
This is in SQL Server, hopefully the syntax works for you too:
SELECT
MV.*
FROM
(
SELECT
team, gameid, min(max_minions) as maxmin
FROM
MinionView
GROUP BY
team, gameid
) groups
JOIN MinionView MV ON
MV.team = groups.team
AND MV.gameid = groups.gameid
AND MV.max_minions = groups.maxmin
In words, first you make the usual grouping query (the nested one). At this point you have the min value for each group but you don't know to which row it belongs. For this you join with the original table and match the "keys" (team, game and min) to get the other columns as well.
Note that if a team will have more than one member with the same value for max_minions then all these rows will be selected. If you only want one of them then that's probably a bit more complicated.
I have two T-SQL scalar functions that both perform calculations over large sums of data (taking 'a lot' of time) and return a value, e.g. CalculateAllIncomes(EmployeeID) and CalculateAllExpenditures(EmployeeID).
I run a select statement that calls these and returns results for each Employee. I also need the balance of each employee calculated as AllIncomes-AllExpenditures.
I have a function GetBalance(EmployeeID) that calls the two above mentioned functions and returns the result {CalculateAllIncomes(EmployeeID) - CalculateAllExpenditures(EmployeeID)}. But if I do:
Select CalculateAllIncomes(EmployeeID), CalculateAllExpenditures(EmployeeID), GetBalance(EmployeeID) .... the functions CalcualteAllIncomes() and CalculateAllExpenditures get called twice (once explicitly and once inside the GetBalance funcion) and so the resulting query takes twice as long as it should.
I'd like to find some better solution. I tried:
select alculateAllIncomes(EmployeeID), AS Incomes, CalculateAllExpenditures
(EmployeeID) AS Expenditures, (Incomes - Expenditures) AS Balance....
but it throws errors:
Invalid column name Incomes and
Invalid column name Expenditures.
I'm sure there has to be a simple solution, but I cannot figure it out. For some reason it seems that I am not able to use column Aliases in the SELECT clause. Is it so? And if so, what could be the workaround in this case?
Thanks for any suggestions.
Forget function calls: you can probably do it everything in one normal query.
Function calls misused (trying for OO encapsulation) force you into this situation. In addition, if you have GetBalance(EmployeeID) per row in the Employee table then you are CURSORing over the table. And you've now compounded this by multiple calls too.
What you need is something like this:
;WITH cSUMs AS
(
SELECT
SUM(CASE WHEN type = 'Incomes' THEN SomeValue ELSE 0 END) AS Income),
SUM(CASE WHEN type = 'Expenditures' THEN SomeValue ELSE 0 END) AS Expenditure)
FROM
MyTable
WHERE
EmployeeID = #empID --optional for all employees
GROUP BY
EmployeeID
)
SELECT
Income, Expenditure, Income - Expenditure
FROM
cSUMs
I once got a query down from a weekend to under a second by eliminating this kind of OO thinking from a bog standard set based aggregate query.