I have a query as below;
Existing Query - select A,B,C from table1.
Table2 has columns X,Y
The new query should have a new column(D) in the result-set. the value of D will be calculated based on column X.
D's calculation should be D = (C * X), Here to decide the row of column X from table2 -Y can be used in where condition. Y & A are not same but similar
I did not understand what did you mean by "Y & A are not same but similar". I assume Y and A can be used as joining keys. If so, the anwer would be:
SELECT T1.A,T1.B,T1.C,T1.C*T2.X AS D
FROM Table1 T1
JOIN Table2 T2 ON T1.A=T2.Y
I hope this helps!
Related
I am trying to join 2 tables like so:
left join (
select t1.createdate, min(f1.createdate) as mindt, f1.status_aft
from new_table t1
left join new_folder f1 on t1.veh_id = f1.veh_id
where f1.createdate > t1.createdate
group by t1.createdate
) h3
on t1.createdate = h3.createdate
and f1.createdate = h3.mindt
But I am getting an error:
ERROR: column "f1.status_aft" must appear in the GROUP BY clause or be used in an aggregate function
This makes sense because I do not group it, my goal is just to take the value that is in that current row when f1.createdate is min.
For example:
A B C
one 10 a
one 15 b
two 20 c
two 25 d
Becomes
A B C
one 10 a
two 20 c
Because a and c was the values when column B were the lowest after grouping it by column A.
I've seen this answer but I still can't apply it to my scenario.
How can I achieve the desired result?
my goal is just to take the value that is in that current row when f1.createdate is min.
If you want just one row, you can order by and limit:
left join (
select t1.t1.createdate, f1.createdate as mindt, f1.status_aft
from new_table t1
left join new_folder f1 on t1.veh_id = f1.veh_id
where f1.createdate > t1.createdate
order by t1.createdate limit 1
) h3
So I have three tables (A, B, C). In tables A and B I have points, and I want to insert into C each row from A, and some columns from the closest point from B to each point in A, as well as the distance between them. I know that the query to get the nearest neighbour is this:
SELECT DISTINCT ON (A.id5) A.state, B.way, st_distance (A.geom,B.geom) INTO C
FROM A, B
WHERE ST_DWithin(A.geom, B.geom, 150)
ORDER BY A.objectid, ST_Distance(A.geom,A.geom)
But I need to get that into a bigger INSERT query, and I tried to do it this way:
INSERT INTO complete(id_door, distance, id_way,Y, X, geom, check)
(SELECT A.state, (select distinct on (A.id5) ST_DISTANCE(A.geom,B.geom) from A order by A.id5, st_distance(A.geom,B.geom)), b.way, ST_Y(B.geom), ST_X(B.geom) ,B.geom, V.check
FROM A, B, C, V
WHERE
ST_INTERSECTS(A.geom, V.geom)\
AND ST_DWithin(A.geom, B.geom,150))
But this is not the right way, because I get the error:
psycopg2.ProgrammingError: more than one row returned by a subquery used as an expression
I cannot copy all the distances from A and B to C and then delete all but the closest because it is a huge table and I would run out of memory, so I need a way to only insert the rows with the info from the closest point from B to A.
What am I doing wrong here? Thank you in advance
UPDATE:
After some help, I have learned that I should use a Lateral in the Select query, but I'm not sure how to use it.
I need the Select to get each row in table A and find its nearest neighbour from table B, which I guess it is done using the query previously stated, and insert into table C some columns from A, some columns from its nearest neighbour (table B), and some columns from table V, which is selected by an Intersect condition. The main problem is how to organize all that into the Select so I don't get an error.
This is where I am at this point:
INSERT INTO C (id_door, distance, id_way,Y, X, geom, check)
(SELECT A.state, l.*, V.check
FROM A, B, C, V
lateral (select st_distance(a.geom,b.geom), b.way, ST_Y(B.geom), ST_X(B.geom) ,B.geom
From B
Where ST_DWithin(a.geom, b.geom,150))
Order by a.geom<->b.geom limit 1) l
WHERE
ST_INTERSECTS(A.geom, V.geom)
You can use lateral join - very smart type of subquery that can reference tables outside the subquery. More about lateral you can find here
-- Edited according to new information in answer --
Insert into C (id_door, distance, id_way,Y, X, geom, check)
select l.*
from a,
lateral (select a.state, st_distance(a.geom,b.geom),
b.way, ST_Y(B.geom), ST_X(B.geom), B.geom,
v.check
from b, v
where ST_DWithin(a.geom, b.geom,150)
and st_dwithin(a.geom,v.geom,0)
and st_intersects(a.geom,v.geom)
order by a.geom<->b.geom, v.geom limit 1) l
If you want more records per each point from A then increase the limit from 1 to your desired value.
I have this SQL
Select A, B, D from T
Where not exists (select F, S from Z)
Can I do the same thing using NOT IN for more than one column ?
Some databases (eg postgresql) have support for row values, where you can do something like ROW(x, y) NOT IN (select f, s from z), Firebird unfortunately does not have row values, so you cannot have more than one column in an IN (or NOT IN).
However you can usually emulate it with a correlated subquery in the exists, eg:
SELECT A, B, D
FROM T
WHERE NOT EXISTS (
SELECT 1
FROM Z
WHERE Z.F = T.X AND Z.S = T.Y
)
Note that EXISTS doesn't care about the selected values, but just that one or more rows were produced, so the two columns you use in your select within the EXISTS are not relevant (it could just as well have been 1 as I used above).
I have a Table which has 2 fields say A,B. Suppose A has values a1,a2.
Corresponding records for a1 in B are 1,2,3,x,y,z.
Corresponding records for a2 in B are 1,2,3,4,d,e,f
I need a a query to be written in DB2, so that it will fetch the common records in B for each record in A (a1 and a2).
So here the output would be :
A B
a1 1
a1 2
a1 3
a2 1
a2 2
a2 3
Can someone please help on this?
Try something like:
SELECT A, B
FROM Table t1
WHERE (SELECT COUNT(*) FROM Table t2 WHERE t2.B = t1.B)
= (SELECT COUNT(DISTINCT t3.A) FROM Table t3)
ORDER BY A, B
This might not be 100% accurate as I can't test it out in DB2 so you might have to tweak the query a little bit to make it work.
with t(num) as (select count(distinct A) from table)
select t1.A, t1.B
from table t1, table t2, t
where t1.B = t2.B
group by t1.A, t1.B, num
having count(*) = num
Basically, the idea is to join the same table with column B and filter out just the ones that match exactly the same number of times as the number of elements in column A, which indicates that it is a common record out of all the A values.
In my procedure I have two tables with the same data. I go through my first table through a cursor. Which compares with the second table that I find much the same data. What if, for example in my table_1 I have ten in my data and I have 12 data table2 how to detect missing data in my two table_1 which is traversed by the cursor?
Thx.
Sounds very much like you'd be better off using the MINUS operator.
SELECT a, b, c
FROM table1
MINUS
SELECT a, b, c
FROM table2
This will show you all results that exist in table1 which are not present in table2. In order to show discrepancies both ways, you could do something like this:
SELECT z.*, 'In table1, not in table2' problem_description
FROM (
SELECT a, b, c
FROM table1
MINUS
SELECT a, b, c
FROM table2
) z
UNION ALL
SELECT z.*, 'In table2, not in table1' problem_description
FROM (
SELECT a, b, c
FROM table2
MINUS
SELECT a, b, c
FROM table1
) z
SQL Fiddle for this answer