I have two postgres tables where one column listing a city name matches. I'm trying to create a view of some records which I'm displaying on a map via WMS on my GeoServer.
I need to select only records from table1 of 100k records that has a city name that matches those cities listed in table2 of 20 records.
To list everything I've tried would be a waste of your time. I've tried every join tutorial and example but, am perplexed why I can't get any success. I would really appreciate some direction.
Here's a latest query but, if this is the wrong approach just ignore since I have about 50 similar attempts.
SELECT t1.id,
t1.dba,
t1.prem_city,
t1.geom
t2.city_label
FROM schema1.table1 AS t1
LEFT JOIN schema2.table2 AS t2
ON t2.city_label = t1.prem_city;
Thanks for any help!
Your query seems correct, just a minor change - LEFT JOIN keeps all the records from the left table and only the matching record from the right one. If you want only those that appear in both - an INNER JOIN is required .
SELECT t1.id,
t1.dba,
t1.prem_city,
t1.geom,
t2.city_label
FROM schema1.table1 t1
JOIN schema2.table2 t2
ON t2.city_label = t1.prem_city;
Related
table_1 has 35 columns, table_2 has 20 columns
query is:
select table1.*,
table2.f1,
...
table2.f20
FROM public.table_1 as table1
left join public.table_2 as table2
on table1.id = table2.id
and table1.arrival_time::date <= table2.end_date::date
and table2.activity_date < table2.end_date
;
this works I expect 469 rows to be returned and that's what I get. However several fields from table_1 get displayed as null instead of the values in the table.
These fields are NOT part of the join.
Due to IP concerns I can't provide the full details of the tables, each field in table_1 and table_2 are varchar (don't ask me why a timestamp is stored as a varchar - its a long story that I have no control over)
This query WORKS in RDS PostgreSQL!
Any ideas why it has a problem in redshift?
Well I'll be very confused.
table_1 is data from two sources joined together - I didn't even think to look at the sources. Turns out the linked source had no data for one value.
Just goes to show that when looking at just a piece of the data you need to look HARD at all the data.
Now I'm off to find a better source for the missing data.
Thanks for your time!
James
I have a view and two tables. Tables one and two have the same columns, but table one is has as small number of records, and table two has old data and a huge number of records.
I have to join a view with these two tables to get the latest data from table one; if a record from the view is not available in table one then I have to select the record from table two.
How can i achieve this with MySQL?
I came to know by doing some research in internet that we can't apply full join and sub query in from clause.
Just do a simple UNION of the results excluding the records in table2 that are already mentioned in table1:
SELECT * FROM table1
UNION
SELECT * FROM table2
WHERE NOT EXISTS (SELECT * FROM table1 WHERE table2.id = table1.id)
Something like this.
SELECT *
FROM view1 V
INNER JOIN (SELECT COALESCE(a.commoncol, b.commoncol) AS commoncol
FROM table1 A
FULL OUTER JOIN table2 B
ON A.commoncol = B.commoncol) C
ON v.viewcol = c.commoncol
If you are using Mysql then check here to simulate Full Outer Join in MySQL
are you trying to update the view from two tables where old record in view needs to be overwritten by latest/updated record from table1 and non existant records from table1 to be appended from table2?
, or are you creating a view from two tables?
I have a bit complicated request to do in HQL and I don't manage to obtain the result I want.
Here is what I want to do :
I have two entities t1 and t2 with a OneToMany relation between both.
I want to select some infos from both tables in the same request but here is the issue, I don't want any duplicate of t1.
So basically I want 4 properties, 3 from t1 and 1 from t2, but as there are several records from t2 for the same t1 object, I just want to get the first from t2 to not have any t1 duplicated records.
Here is what I did :
SELECT DISTINCT(t1.a , t1.b, t1.c, t2.z) FROM t1 LEFT JOIN t2
But Obviously, that worked when I did not need any t2 parameter, but now I have some records (a,b,c) duplicated for different t2.z
And I don't find any way in HQL to do it (I can't do any Select LIMIT 1 that could work in SQL).
Does anybody have an idea on how to resolve that?
Thanks
Can someone explain multiple left join logic?
For example i have 3 tables: Company, company_text, company_rank.
Company has 4 records (id's: 1,2,3,4), company_text has 4 records with company names (1-a,2-b,3-c, 4-d), company_rank has following (1-1st, 2-2nd, 3-3rd). Note that company_rank table is not having 4th record. Now i want records of all companies using LEFT join. In case if there is no rank, display as 'zzzz' and sort in the descending order of rank and when rank is null sort by descending order of id.
select * from company
LEFT JOIN company_text ON company.id = company_text.id
LEFT JOIN company_rank ON company_text.id = company_rank.id
order by isnull(company_rank.rank,'zzzz'), rank desc
Will this work?
Basically i am trying to understand how LEFT JOIN works if there are many left joins? This doc. has good info on joins: http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html but it don't have information on how multiple LEFT JOINS work? In case if multiple joins are present, how records data will be pulled?
I've been using SQLPLUS lately and one of my tasks was to display a set of values from two tables (stocks, orderitems). I have done this part, but I am stuck on the last part of the question which states: "including the stocks that no order has been placed on them so far".
Here is the statement:
`select Stocks.StockNo, Stocks.Description, OrderItems.QtyOrd
from Stocks INNER JOIN OrderItems
ON Stocks.StockNo = OrderItems.StockNo;`
and I have gotten the correct results for this part, but the second part is eluding me, as the curernt statement doesn't display the 0 values for QtyOrd.
Any help would be appreciated.
You likely want to use a LEFT OUTER JOIN otherwise the INNER JOIN will exclude Stocks which don't have any Orders. You might also consider grouping by Stock, in order to SUM the overall quantities for each stock?
SELECT Stocks.StockNo, Stocks.Description, SUM(OrderItems.QtyOrd) AS QtyOrd
FROM Stocks
LEFT OUTER JOIN OrderItems
ON Stocks.StockNo = OrderItems.StockNo
GROUP BY Stocks.StockNo, Stocks.Description;