I have joined two tables and fetched data using Postgres source connector. But every time it gave the same issue i.e.
I have run the same query in Postgres and it runs without any issue. Is fetching data by joining tables not possible in Kafka?
I solve this issue by using the concept of the subquery. The problem was that
when I use an alias, the alias column is interpreted as a whole as a column name and therefore the problem occurs. Here goes my query:
select * from (select p.\"Id\" as \"p_Id\", p.\"CreatedDate\" as p_createddate, p.\"ClassId\" as p_classid, c.\"Id\" as c_id, c.\"CreatedDate\" as c_createddate, c.\"ClassId\" as c_classid from \"PolicyIssuance\" p left join \"ClassDetails\" c on p.\"DocumentNumber\" = c.\"DocumentNo\") as result"
Related
Anyone know what is the ORM function for joining multiple db tables in ERPNext?
I need query result from 2 DB tables join using script report
*I don't need query report answer since i already have it. I only looking for an example do it using script report
Frappe currently doesn't have ORM support for joining tables. You might have to use frappe.db.sql for the time being.
data = frappe.db.sql(
"""
select tb1.name from tabTable1 as tb1
left join tabTable2 as tb2 on tb1.name = tb2.employee_name;
"""
);
return data
I want to know can we write query using two tables ( join) in flink Table and SQL api.
I am new to flik, I want to create two table from two different data set and query them and produce other dataset.
my query would be like select... from table1, table 2... so can we write like this query which querying two tables or more?
Thanks
Flink's Table API supports join operations (full, left, right, inner joins) on batch tables (e.g. those created from a DataSet).
SELECT c, g FROM Table3, Table5 WHERE b = e
For streaming tables (e.g. those created from a DataStream), Flink does not yet support join operations. But the Flink community is actively working to add them in the near future.
I have data on table T1 in database DB1.
I need move to the table T2 in database DB2 only those rows of T1 that have Field F1 equals to certain values.
These values are on a table TC in database DB2. DB1 cannot refer to DB2 therefore in the DataFlow Component of my dtsx I cannot write a query with a join between T1 and TC.
I see two possible paths:
I could first import all the rows from T1 then filter them in the dtsx before pouring them in T2
Instead of having a SQL query to get the data from DB1 I could write a stored procedure in DB1 that accepts a table valued parameter and then I could try (I don't know how) to put my parameters (1,2,4 in the example) in the TVP and invoke the stored procedure with this.
I have to do this kind of import for dozens of tables therefore solution 2 seems really too convoluted and complicated. Solution 1 seems to do too much useless work, first importing everything and then discarding part of what was imported.
Is there a best practice or smart trick in this case?
Thank you
You can use a merge join to join data from T1 and Tc on field F1. So two data source, one for T1, one for TC. No parameters are applied yet. You need to use a sort component to sort on the join field (F1) in both result sets for the merge join to work. Then define a join type (inner) in merge join component. This is where the parameters from TC are applied to T1, so you use a inner join to apply the parameters. Finally export the result to T2.
Another way is just import everything from T1 to a temp table on DB2, call it T2_temp, then you can use a query to join T2_temp with TC on F1, then insert the result to T2.
Okay. So the question that I got asked by the teacher was this:
(5 marks) Construct a SQL query on the dvdrental database that uses a natural join of two or more tables and an additional where condition. (E.g. find the titles of films rented by a particular customer.) Note the hints on the course news page if your query returns nothing.
Here is the layout of the database im working with:
http://www.postgresqltutorial.com/wp-content/uploads/2013/05/PostgreSQL-Sample-Database.png
The hint to us was this:
PostgreSQL hint:
If a natural join doesn't produce any results in the dvdrental DB, it is because many tables have the last update: timestamp field, and thus the natural join tries to join on that field as well as the intended field.
e.g.
select *
from film natural join inventory;
does not work because of this - it produces an empty table (no results).
Instead, use
select *
from film, inventory
where film.film_id = inventory.film_id;
This is what I did:
select *
from film, customer
where film.film_id = customer.customer_id;
The problem is I cannot get a particular customer.
I tried doing customer_id = 2; but it returns a error.
Really need help!
Well, it seems that you would like to join two tables that have no direct relation with each other, there's your issue:
where film.film_id = customer.customer_id
To find which films are rented by which customer you would have to join customer table with rental, then with inventory and finally with film.
The task description states
Construct a SQL query on the dvdrental database that uses a natural join of two or more tables and an additional where condition.quote
I am trying to get the last date an insert was performed in a table (on Amazon Redshift), is there any way to do this using the metadata? The tables do not store any timestamp column, and even if they had it, we need to find out for 3k tables so it would be impractical so a metadata approach is our strategy. Any tips?
All insert execution steps for queries are logged in STL_INSERT. This query should give you the information you're looking for:
SELECT sti.schema, sti.table, sq.endtime, sq.querytxt
FROM
(SELECT MAX(query) as query, tbl, MAX(i.endtime) as last_insert
FROM stl_insert i
GROUP BY tbl
ORDER BY tbl) inserts
JOIN stl_query sq ON sq.query = inserts.query
JOIN svv_table_info sti ON sti.table_id = inserts.tbl
ORDER BY inserts.last_insert DESC;
Note: The STL tables only retain approximately two to five days of log history.