I'm running what I think should be a very simple query. All I want to do is select the COUNT of values if one field status is set to Y (for yes) and there is a year entry (i.e.: 1997). I've written the following query and it does not seem to find a result when it should be listed.
Query:
SELECT COUNT(1) FROM mydb WHERE status = 'Y' AND year IS NOT NULL
It doesn't seem to be picking up when I do have an integer value for my year column. Why is this the case?
Related
I have the following table in PostgreSQL DB:
DB exempt
I need a PostgreSQL command to get a specific value from tbl column, based on time_launched and id columns. More precisely, I need to get a value from tbl column which corresponds to a specific id and latest (time-wise) value from time_launched column. Consequently, the request should return "x" as an output.
I've tried those requests (using psycopg2 module) but they did not work:
db_object.execute("SELECT * FROM check_ids WHERE id = %s AND MIN(time_launched)", (id_variable,))
db_object.execute(SELECT DISTINCT on(id, check_id) id, check_id, time_launched, tbl, tbl_1 FROM check_ids order by id, check_id time_launched desc)
Looks like a simple ORDER BY with a LIMIT 1 should do the trick:
SELECT tbl
FROM check_ids
WHERE id = %s
ORDER BY time_launched DESC
LIMIT 1
The WHERE clause filters results by the provided id, the ORDER BY clause ensures results are sorted in reverse chronological order, and LIMIT 1 only returns the first (most recent) row
This question already has an answer here:
Postgresql - Compare a string with a null value
(1 answer)
Closed last month.
I red a bunch of questions about handling NULL values in rust-postgresql, but they don't mention my personal case.
I need to select rows using a WHERE with a parameter that can be NULL, like
SELECT id FROM TABLE WHERE name=$1
If the Option used to set $1 is None, it doesn't retrieve any rows.
So i have to split the query under a IF, like
if myname.is_some()
SELECT id FROM TABLE WHERE name=$1
else
SELECT id FROM TABLE WHERE name=NULL
There is a better way to handle a NULL in a WHERE clause with a single line of code?
I tried to handle it with the "default" way.
I hope there is a faster way.
If a NULL parameter means "all rows" you can use an OR:
SELECT id
FROM TABLE
WHERE name = $1
OR $1 IS NULL;
If you want to find those where the name is NULL if the parameter is NULL, you can use IS NOT DISTINCT FROM:
SELECT id
FROM TABLE
WHERE name is not distinct from $1
I have table like below. For distinct combination of user ID and Product ID SQL will select product bought from store ID 1 or 2? Is it determinictic?
My code
SELECT (DISTINCT CONCAT(UserID, ProductID)), Date, StoreID FROM X
This isn't valid syntax. You can have
select [column_list] from X
or you can have
select distinct [column_list] from X
The difference is that the first will return one row for every row in the table while the second will return one row for every unique combination of the column values in your column list.
Adding "distinct" to a statement will reliably produce the same results every time unless the underlying data changes, so in this sense, "distinct" is deterministic. However, it is not a function so the term "deterministic" doesn't really apply.
You may actually want a "group by" clause like the following (in which case you have to actually specify how you want the engine to pick values for columns not in your group):
select
concat(UserId, ProductID)
, min(Date)
, max(Store)
from
x
group by
concat(UserId, ProductID)
Results:
results
I have a query :
select distinct(donorig_cdn),cerhue_num_rfa,max(cerhue_dt) from t_certif_hue
group by donorig_cdn,cerhue_num_rfa
order by donorig_cdn
it returns me some repeated ids with different cerhue_num_rfa
how do i return only one line for the repeated ids with cerhue_num_rfa that matches the max of date (cerhue_dt) .. and have at the end only 10 results instead of 15 ?
Postgres has SELECT DISTINCT ON to the rescue. It only returns the first row found for each value of the given column. So, all you need is an order that ensures the latest entry comes first. No need for grouping.
SELECT DISTINCT ON (donorig_cdn) donorig_cdn,cerhue_num_rfa,cerhue_dt
FROM t_certif_hue
ORDER BY donorig_cdn, cerhue_dt DESC;
I have two tables on a Sql Server 2008.
ownership with 3 fields and case with another 3 fields I need to join both on the ID field (bigint).
For testing purposes I'm only using one field from each table. This field is bigint and has values from 1 to 170 (for now).
My query is:
SELECT DISTINCT
ownership.fCase,
case.id
FROM
ownership LEFT JOIN case ON (case.id=ownership.fCase)
WHERE
ownership.dUser='demo'
This was expected to return 4 rows with the same values on both columns. Problem is that the last row of the right table comes as null for the fCase = 140. This is the only value above 100.
If I run the query without the WHERE clause it show all rows on the left table but the values on the right only apear if below 101 otherwise shows null.
Can someone help me, am I doing something wrong or is this a limitation or a bug?
Case is also a verb so it may be getting confused. Try your table and column names in []. E.G. [case].[id] = [ownership].[fCase]. Are you like double check sure that [case].[id] and [ownership].[fCase] are both bigint. If your current values are 1-170 then why bigint (9,223,372,036,854,775,807)? Does that column accept nulls?