I would like to add to the table A all the column of the table B, doing a join based on a common column (type numeric). I am trying to do it using the LEFT JOIN but the columns added are all blank. this is impossible because table b stores, among others, the same ID values . Where I am wrong?
Select * from "2017_01" left join "Registry_2017" on '2017_01.ID' = 'Registry_2017.ID';
You are doing wrong.. I don't know why you can use right for Table calling "2017_01" and different with this '2017_01.ID'..
' = Single quote identifies as String
" = Double quote identifies as Table or Column to escape Naming
Select
*
From
"2017_01"
left join "Registry_2017" on '2017_01.ID' = 'Registry_2017.ID';
So when you doing this '2017_01.ID' = 'Registry_2017.ID' The condition will always become false because those 2 different String are not equal. Postgresql look the condition not as Table and Column but String because you are using Single quote
Select
*
from
"2017_01"
left join "Registry_2017" on "2017_01"."ID" = "Registry_2017"."ID";
So the query should be like that.. Even you already got answer and it got work i must tell this..
Related
I am trying to create a new table by using inner join to combine multiple tables. All, the tables have a primary key/column called reach_id. I have a primary table called q3_studies. I want all of the columns from this table. I then have multiple other tables that have reach_id + another column. I want to JOIN this table ON reach_id that matches q3_studies but only include the other columns (so I don't have redundant reach_id columns). My first attempt seems to work if I run it from SELECT * ... using a LIMIT 1000; at the end, but adds redundant reach_ids.
SELECT * FROM second_schema.q3_studies s
INNER JOIN second_schema.bs_trigger_q3 b ON s.reach_id = b.reach_id
INNER JOIN second_schema.mod_unmod_q3 m ON s.reach_id = m.reach_id LIMIT 1000;
How can I amend this to add only the additional columns (ex: bs_trigger_q3 has an additional columns called bs_trigger, mod_unmod_q3 has an additional column called mod_unmod)?
Secondly, if I try to create a new table, I get an error: column reach_id specified more than one. What am I doing wrong here?
CREATE TABLE first_schema.report_q3 AS
SELECT * FROM second_schema.q3_studies s
INNER JOIN second_schema.bs_trigger_q3 b ON s.reach_id = b.reach_id
INNER JOIN second_schema.mod_unmod_q3 m ON s.reach_id = m.reach_id;
Instead of select * you need to list the columns you want explicitly. This is good practice in any case. It also allows you to rename columns e.g. s.column_A as "foo_column"
In the future the schema may change.
CREATE TABLE first_schema.report_q3 AS
SELECT
s.reach_id,
s.column_A, s.column_B,
b.column_C, b.column_D,
m.column_E, m.column_F
FROM second_schema.q2_studies s
INNER JOIN second_schema.bs_trigger_q3 b ON s.reach_id = b.reach_id
INNER JOIN second_schema.mod_unmod_q3 m ON s.reach_id = m.reach_id
;
If your editor does not help you with column names consider a different editor.
I have a table with columns FIRSTNAME LASTNAME and I want to create a third column that combines those two columns into FIRSTNAME_LASTNAME but ALSO uses a special dictionary to convert some of the names. Say I just want to apply it to the FIRSTNAME, e.g.:
Albert -> Funnyguy, Kathleen -> Nerd, Megan -> Weirdo
So the new column for the "Albert Jones" row would be "Funnyguy_Jones".
Currently I do this in psycopg2 by reading in all the rows (in batches because the db is huge), using a python dictionary to convert and create the new column, then sending out the updates with UPDATE table SET newcol = tmp.newcol FROM (VALUES ...) etc. This is very slow because of reading it into python. Any tips?
EDIT: not all of the names have conversions (only like 10% of them do, for those I want to keep the original name)
If left join has a match COALESCE will choose t2.newName, other wise you will choose t1.firstName
SELECT t1.firstName,
t1.lastName,
COALESCE(t2.newName, t1.firstName) + '_' + t1.lastName as combinedName
FROM firstTable t1
LEFT JOIN newTable t2
ON t1.firstName = t2.firstName
I'm trying to decipher another programmer's code who is long-gone, and I came across a select statement in a stored procedure that looks like this (simplified) example:
SELECT #Table2.Col1, Table2.Col2, Table2.Col3, MysteryColumn = CASE WHEN y.Col3 IS NOT NULL THEN #Table2.MysteryColumn - y.Col3 ELSE #Table2.MysteryColumn END
INTO #Table1
FROM #Table2
LEFT OUTER JOIN (
SELECT Table3.Col1, Table3.Col2, Col3 = SUM(#Table3.Col3)
FROM Table3
INNER JOIN #Table4 ON Table4.Col1 = Table3.Col1 AND Table4.Col2 = Table3.Col2
GROUP BY Table3.Col1, Table3.Col2
) AS y ON #Table2.Col1 = y.Col1 AND #Table2.Col2 = y.Col2
WHERE #Table2.Col2 < #EnteredValue
My question, what does the fourth column of the primary selection do? does it produce a boolean value checking to see if the values are equal? or does it set the #Table2.MysteryColumn equal to some value and then inserts it into #Table1? Or does it just update the #Table2.MysteryColumn and not output a value into #Table1?
This same thing seems to happen inside of the sub-query on the third column, and I am equally at a loss as to what that does as well.
MysteryColumn = gives the expression a name also called a column alias. The fact that a column in the table#2 also has the same name is besides the point.
Since it uses INTO syntax it also gives the column its name in the resulting temporary table. See the SELECT CLAUSE and note | column_alias = expression and the INTO CLAUSE
I have tried this:
SELECT *
FROM svc00100
WHERE NOT EXISTS (SELECT *
FROM svc00101
WHERE TECHSTAT = 'INA'
AND svc00100.TECHID = svc00101.TECHID)
I want to select rows from svc00100 but not if there is a row in svc00101 with the same TECHID and with TECHSTAT = 'INA'. But, there are multiple rows in svc00101 with the TECHID matching, some having 'INA' and some having other stuff. I want to eliminate/ignore any TECHID where there is any row in svc00101 with TECHID and 'INA' for techstat. Using SQL server BTW if that helps.
You can use left outer join and Where clause. Like this:
select svc00100.* from svc00100
left outer join svc00101 on TECHSTAT = "INA"
and svc00100.TECHID = svc00101.TECHID
where svc00101.KEY is null
Instead of KEY you should pass name of NOT NULL column. For example Primary Key.
In my application i have a query that do multiple joins with a table position. Just like this:
SELECT *
FROM (...) as trips
join trip as t on trips.trip_id = t.trip_id
left outer join vehicle as v on v.vehicle_id = t.trip_vehicle_id
left outer join position as start on trips.start_position_id = start.position_id and start.position_vehicle_id = v.vehicle_id
left outer join position as "end" on trips.end_position_id = "end".position_id and "end".position_vehicle_id = v.vehicle_id
left outer join position as last on trips.last_position_id = last.position_id and last.position_vehicle_id = v.vehicle_id;
My table position has 35 columns(for example position_id).
When I run the query, in result should appear the table position 3 times, start, end and last. But postgres can not distinguish between, for exemplar, start.position_id, end.position_id and last.position_id. So this 3 columns are group and appear as one, position_id.
As the data from start.position_id and end.position_id are different, the column, position_id, that appear in result, it's empty.
Without having to rename all the columns, like this: start.position_id as start_position_id.
How can i get each group of data separately, for exemple, get all columns from the table 'start'. In MYSQL i can do this operation by calling fetch_fields, and give the function an alias, like 'start'.
But i can i do this in Postgres?
Best Regards,
Nuno Oliveira
My understanding is that you can't (or find it difficult to) discern between which table each column with a shared name (such as "position_id") belongs to, but only need to see one of the sets of shared columns at any one time. If that is the case, use tablename.* in your SELECT, so SELECT trips.*, start.*... would show the columns from trips and start, but no columns from other tables involved in the join.
SELECT [...,] start.* [,...] FROM [...] atable AS start [...]