I am working with deno and using denodb ORM and I am trying and looking at documentation from last couple of hours how to use ORM and after sometime I am stuck that how to query the following sql query using denodb ORM?
query:
SELECT COUNT(*) AS count from table WHERE field1 = 1 AND field2 = 2 OR field3 = 3
I am confused how to use OR, AND, etc Operator using this denodb package.
Thanks
They are not implemented as of this time. See eveningkid/denodb#197.
Related
I am doing performance analysis over mondial database using sqlite3. One test case where I have to compare performance with and without using index (it should not use sqlite_autoindex as well).
I found this link :How can I force a query to not use a index on a given table? very useful but most of the answers refer to SQL SERVER. But I need it for SQLITE3. (I have tried PRAGMA options but no result).
It's buried in the syntax diagrams for SELECT, but there is a way - Using NOT INDEXED with a table name in the FROM clause:
sqlite> CREATE TABLE foo(bar);
sqlite> CREATE INDEX foo_idx ON foo(bar);
sqlite> EXPLAIN QUERY PLAN SELECT * FROM foo WHERE bar = ?;
QUERY PLAN
`--SEARCH TABLE foo USING COVERING INDEX foo_idx (bar=?)
sqlite> EXPLAIN QUERY PLAN SELECT * FROM foo NOT INDEXED WHERE bar = ?;
QUERY PLAN
`--SCAN TABLE foo
As you can see, the first query uses the index, and the second one doesn't.
How to read EXPLAIN QUERY PLAN output.
I am using SQLite3 with Python. I am quite certain that the 'WHERE' clause does not work with 'INSERT' operation, but I really need to have a workaround to solve my issue. I have the following prepopulated database:
I was hoping to come up with an SQL statement where I can add the VALUES ('2021-01-13', '36.8') to the table WHERE family='FAA' AND model='MAA'. I have read a lot of stuff online but still no luck on my side.
I think you want an update here:
UPDATE yourTable
SET date = '2021-01-13', duration = 36.8
WHERE family = 'FAA' AND model = 'MAA';
You want to update your table, insert is only for new rows. When you want to change a value, you must to use update statement.
UPDATE table_name
SET date = '2021-01-13', duration = '36.8'
WHERE family='FAA' AND model='MAA';
https://www.sqlite.org/lang_update.html
I am doing performance analysis over mondial database using sqlite3. One test case where I have to compare performance with and without using index (it should not use sqlite_autoindex as well).
I found this link :How can I force a query to not use a index on a given table? very useful but most of the answers refer to SQL SERVER. But I need it for SQLITE3. (I have tried PRAGMA options but no result).
It's buried in the syntax diagrams for SELECT, but there is a way - Using NOT INDEXED with a table name in the FROM clause:
sqlite> CREATE TABLE foo(bar);
sqlite> CREATE INDEX foo_idx ON foo(bar);
sqlite> EXPLAIN QUERY PLAN SELECT * FROM foo WHERE bar = ?;
QUERY PLAN
`--SEARCH TABLE foo USING COVERING INDEX foo_idx (bar=?)
sqlite> EXPLAIN QUERY PLAN SELECT * FROM foo NOT INDEXED WHERE bar = ?;
QUERY PLAN
`--SCAN TABLE foo
As you can see, the first query uses the index, and the second one doesn't.
How to read EXPLAIN QUERY PLAN output.
I am trying to fetch set of records from the database part by part.
I tried to use Limit and fetch but it seems like it does not working with oracle 11g. Is there any alternative solution to do this. I have tried many in google results but nothing is working properly.
You can use this query and do what u want.
SELECT A.*
FROM (SELECT A.*, ROWNUM ROWNUMBER
FROM Table1 T
WHERE ROWNUM <= TO) T
WHERE ROWNUMBER > FROM;
FROM is from which number and TO is to which number
A Sound application is based on sound design. Kindly check if you are trying to achieve a procedural requirement using an SQL. If yes, it is better to use PL/SQL instead of SQL.
Create a cursor using the required SQL without any limits.
Create a type of associative array to hold the batch records.
Create an associative array using the type created above
Open and loop the cursor.
FETCH created_cursor BULK COLLECT INTO created_associated_array LIMIT ;
Hope this helps.
I have a trivial issue that I can't resolve. Currently our app uses Linq to retrieve data and get a basic integer value of the row count. I can't form a query that gives back a count without a 'select i'. I don't need the select, just the count(*) response. How do I do this? Below is a sample:
return (from io in db._Owners
where io.Id == Id && io.userId == userId
join i in db._Instances on io.Id equals i.Id **select i**).Count()
;
The select i is fine - it's not actually going to be fetching any data back to the client, because the Count() call will be translated into a Count(something) call at the SQL side.
When in doubt, look at the SQL that's being generated for your query, e.g. with the DataContext.Log property.
Using the LINQ query syntax requires a select statement. There's no way around that.
That being said, the statement will get transformed into a COUNT()-based query; the select i is there only to satisfy the expression system that underlies the LINQ query providers (otherwise the type of the expression would be unknown).
Including the select will not affect the performance here because the final query will get translated into SQL. At this point it will be optimized and will be like select (*) from ......