I want to translate this SQL query, in JOOQ.
I want the new field from calculated value, but here i just add it with constant value.
select
*,
100 as "newField"
from author
I tried this
Result<Record> r=create.select(DSL.asterisk(),DSL.val(100).as("newField"))
.from(DSL.table("author"))
.fetch();
That generates this SQL (which looks fine)
select
*,
? as "newField"
from author
But i get this as result (expected is all table with 1 extra column with value 100)
+--------+
|newField|
+--------+
|1 |
|2 |
+--------+
In pgAdmin, the sql above query does what i need(adds a new field to the table with all values 100).
I don't know what i do wrong, the results seems like newField gets as value the row number.
Also in SQL generation how i can print the SQL with the 100 value instead of ?
This is a known limitation, the usage of asterisk() with a plain SQL query is limited: https://github.com/jOOQ/jOOQ/issues/7841
Workarounds include:
Using the code generator (which is always a good idea)
Wrapping the query in another derived table, and selecting the asterisk() alone in the outer most query
Also in SQL generation how i can print the SQL with the 100 value instead of ?
That's a different question, not strictly related. There are various ways to generate inline values in jOOQ. In your case, probably Query.getSQL(paramType.INLINED) could help you "print" the SQL. Though, you might have had something else in mind, in case of which I recommend asking a new question with more details about this.
Related
I have one table customer_info in a Cassandra DB & it contains one column as billing_due_date, which is date field (dd-MMM-yy ex. 17-AUG-21). I need to fetch the certain fields from customer_info table based on billing_due_date where billing_due_date should be equal to system date +1.
Can anyone suggest a Cassandra DB query for this?
fetch the certain fields from customer_info table based on billing_due_date
transaction_id is primarykey , It is just generated through uuid()
Unfortunately, there really isn't going to be a good way to do this. Right now, the data in the customer_info table is distributed across all nodes in the cluster based on a hash of the transaction_id. Essentially, any query based on something other than transaction_id is going to read from multiple nodes, which is a query anti-pattern in Cassandra.
In Cassandra, you need to design your tables based on the queries that they need to support. For example, choosing transaction_id as the sole primary key may distribute well, but it doesn't offer much in the way of query flexibility.
Therefore, the best way to solve for this query, is to create a query table containing the data from customer_info with a key definition of PRIMARY KEY (billing_date,transaction_id). Then, a query like this should work:
> SELECT * FROM customer_info_by_date
WHERE billing_due_date = toDate(now()) + 2d;
billing_due_date | transaction_id | name
------------------+--------------------------------------+---------
2021-08-20 | 2fe82360-e314-4d5b-aa33-5deee9f03811 | Rinzler
2021-08-20 | 92cb9ee5-dee6-47fe-b372-0829f2e384cd | Clu
(2 rows)
Note that for this example, I am using the system date plus 2 days out. So in your case, you'll want to adjust the "duration" aspect from 2d down to 1d. Cassandra 4.0 allows date arithmetic, so this should work just fine if you are on that version. If you are not, you'll have to do the "system date plus one" calculation on the app side.
Another way to go about this, would be to create a secondary index on billing_due_date, but I don't recommend that path as it will query multiple nodes to build the result set.
I’m using ADODB to query on Sheet1. If I fetch the data using SQL query on the sheet as below without grouping I’m getting all characters from comment.
However, if I use grouping my characters are truncated to 255.
Note – My first row contains 800 len of characters so drivers have identified the datatype correctly.
Here is my query output without grouping
Select Product, Value, Comment, len(comment) from [sheet1$A1:T10000]
With grouping
Select Product, sum(value), Comment, len(comment) from [sheet1$A1:T10000] group by Product, Comment
Thanks for posting this! During my 20+ years of database development using ADO recordsets I had never faced this issue until this week. Once I traced the truncation to the recordset I was really scratching my head. Couldn't figure how/why it was happening until I found your post and you got me focused on the GROUP BY. Sure enough, that was the cause (some kind of ADO bug I guess). I was able to work around it by putting correlated scalar sub-queries in the SELECT list, vice using JOIN and GROUP BY.
To elaborate...
At least 9 times out of 10 (in my experience) JOIN/GROUP BY syntax can be replaced with correlated scalar subquery syntax, with no appreciable loss of performance. That's fortunate in this case since there is apparently a bug with ADO recordset objects whereby GROUP BY syntax results in the truncation of text when the string length is greater than 255 characters.
The first example below uses JOIN/GROUP BY. The second uses a correlated scalar subquery. Both would/should provide the same results. However, if any comment is greater than 255 characters these 2 queries will NOT return the same results if an ADODB recordset is involved.
Note that in the second example the last column in the SELECT list is itself a full select statement. It's called a scalar subquery because it will only return 1 row / 1 column. If it returned multiple rows or columns an error would be thrown. It's also known as a correlated subquery because it references something that is immediately outside its scope (e.emp_number in this case).
SELECT e.emp_number, e.emp_name, e.supv_comments, SUM(i.invoice_amt) As total_sales
FROM employees e INNER JOIN invoices i ON e.emp_number = i.emp_number
GROUP BY e.emp_number, e.emp_name, e.supv_comment
SELECT e.emp_number, e.emp_name, e.supv_comments,
(SELECT SUM(i.invoice_amt) FROM invoices i WHERE i.emp_number = e.emp_number) As total_sales
FROM employees e
I have several tables with bucketing applied. It can work great when I specify the bucket/partition parameter upfront in my SELECT query, however when I retrieve the bucket value I need from a different table - within a WITH select statement, Hive/Athena seems to no longer use the optimisation, and searches the entire database instead. I would like to learn if there is a way to write my query properly to maintain the optimisation.
For a simple example, I have two tables:
Table1
category | categoryid
---------+-----------
mass | 1
Table2
categoryid | index | value
-----------+-------+------
1 | 0 | 15
1 | 1 | 10
1 | 2 | 7
The bucketed/clustered column is categoryid. I have a single category ('mass') and would like to retrieve the value's that correspond with the category I have. So I have designed my SELECT like this:
WITH dataset AS (
SELECT categoryid
FROM Table1
WHERE category='mass'
)
SELECT index,value
FROM Table2, dataset
WHERE Table2.categoryid=dataset.categoryid
This will run, but will search the entire database it seems, because Hive doesn't know the categoryid for bucketing before commencing the search? If I swap out the final Table2.categoryid=dataset.categoryid for Table2.categoryid=1 then it will search only the fraction of the db.
So is there some way of writing this query to ensure Hive doesn't search more buckets in the second table than it has to?
Athena is based on Presto. Unless there is some modification in Athena in this area (and I think there currently isn't), this cannot be made to work in single query.
Recommended workaround: issue one query to gather dataset.categoryid values. Pass them as constant to your main query:
WITH dataset AS (
SELECT category
FROM Table1
WHERE category='mass'
)
SELECT index,value
FROM Table2, dataset
WHERE Table2.categoryid = dataset.categoryid
AND Table2.categoryid IN ( <all possible values> );
This is going to be improved with the additional of Dynamic Filtering in Presto, that the Presto Community is working on currently.
I have a question to query to cassandra collection.
I want to make a query that work with collection search.
CREATE TABLE rd_db.test1 (
testcol3 frozen<set<text>> PRIMARY KEY,
testcol1 text,
testcol2 int
)
table structure is this...
and
this is the table contents.
in this situation, I want to make a cql query has alternative option values on set column.
if it is sql and testcol3 isn't collection,
select * from rd.db.test1 where testcol3 = 4 or testcol3 = 5
but it is cql and collection.. I try
select * from test1 where testcol3 contains '4' OR testcol3 contains '5' ALLOW FILTERING ;
select * from test1 where testcol3 IN ('4','5') ALLOW FILTERING ;
but this two query didn't work...
please help...
This won't work for you for multiple reasons:
there is no OR operation in CQL
you can do only full match on the value of partition key (testcol3)
although you may create secondary indexes for fields with collection type, it's impossible to create an index for values of partition key
You need to change data model, but you need to know the queries that you're executing in advance. From brief looking into your data model, I would suggest to rollout the set field into multiple rows, with individual fields corresponding individual partitions.
But I want to suggest to take DS201 & DS220 courses on DataStax Academy site for better understanding how Cassandra works, and how to model data for it.
Maybe I'm missing something simple, but is there a way to write a nested query in AX? I tried some syntax I thought would work, but with no luck.
The following standard SQL statement would accomplish what I'm trying to do, but I need to do this in AX, not SQL.
SELECT table1.column1A, table1.column1B,
(SELECT Top 1 column2B FROM table2
WHERE table1.column1A = table2.column2A
ORDER BY table2.column1A)
AS lookupResult
FROM table1
My problem is that table1 has a one-to-many relationship with table2, and since AX doesn't have a DISTINCT function that I'm aware of, I receive many copies of each record when using a JOIN statement.
Thanks
Nested queries are not supported in AX.
One way to bypass the missing distinct is to use group by (assuming max value of column2B is interesting):
while select column1A, column1B from table1
group column1A, column1B
join max-of(column2B) from table2
where table2.column2A == table1.column1A
{
...
}
Another method would be use a display method on table1 in the form or report.
display ColumnB column2B()
{
return (select max-of(column2B) from table2
where table2.column2A == this.column1A).column2A;
}
The performance is inferior to the first solution, but it may be acceptable.
As mentioned in the previous reply, group-by is the closest you can get to a distinct function. If you need a simpler query for some reason, or if you need a table or query object to use as a datasource on a form or report, you may entertain the idea of creating a view in the AOT, which contains the group-by. You can then use that view to easily join to on a query object or form datasource etc...
Ax2012 has support of computed columns in views, you can use the SysComputedColumn class to build query you want