I have three array columns in a postgres table.
column array_a has values like {"red","blue","green"}
column array_b has values like {"blue","green"}
I would like to update column array_c to the array from array_a with any value found in array_b removed
so in this case array_c would be {"red"}
update my_table
set array_c = (
array_remove(array_a, UNNEST(array_b)));
works except that if array_b is Null everything is removed.
I can fix that by separating out the query into
WHERE array_b IS NOT NULL
and
WHERE array_b IS NULL
but is there a way to catch the null problem within the original query?
Related
I have column that is returning from my query that is an array of array. It looks like this.
array_vals: {{NULL,NULL,147.89,87.27,82.65,83.41,93.69,101.90,NULL,NULL}}
When I try to query in to my array first array I always get Null values.
select array_vals[0] from table
This returns null. But my desired results would be {NULL,NULL,147.89,87.27,82.65,83.41,93.69,101.90,NULL,NULL}
with test as (
select 1 as value, array_agg(array[1 , 3, 4]) as data
group by value
)
select data[1] from test
This returns null for me.
I'm trying to insert values in a tabla with values inside, like this table:
If you look at the column "202001" and row 22 at the end, it is null, so I want to insert manually any value.
It is null because that value it's not inserted to the database yet.
The expression I have is Sum([SH_historico_1.MONTO]/1000000) (Mounts..)
Any ideas? maybe with that SUM and then concadenate
Please try:
Alt(Sum([SH_historico_1.MONTO]/1000000),0)
where 0 is as you say "any value".
ALt function return first numeric value. So when your function will not return any number, another number is used.
Our system uses postgres for its database.
We have queries that can select rows from a database table where an array field in the table contains a specific value, e.g.:
Find which employee manages the employee with ID 123.
staff_managed_ids is a postgres array field containing an array of the employees that THIS employee manages.
This query works as expected:
select *
from employees
where 123=any(staff_managed_ids)
We now need to query where an array field contains a postgres NULL. We tried the following query, but it doesn't work:
select *
from employees
where NULL=any(staff_managed_ids)
We know the staff_managed_ids array field contains NULLs from other queries.
Are we using NULL wrongly?
NULL can not be compared using =. The only operators that work with that are IS NULL and IS NOT NULL.
To check for nulls, you need to unnest the elements:
select e.*
from employees e
where exists (select *
from unnest(e.staff_managed_ids) as x(staff_id)
where x.staff_id is null);
if all your id values are positive, you could write something like this:
select *
from employees
where (-1 < all(staff_managed_ids)) is null;
how this works is that -1 should be less than all values, however comparison with null will make the whole array comparison expression null.
original query looks like this :
UPDATE reponse_question_finale t1, reponse_question_finale t2 SET
t1.nb_question_repondu = (9-(ISNULL(t1.valeur_question_4)+ISNULL(t1.valeur_question_6)+ISNULL(t1.valeur_question_7)+ISNULL(t1.valeur_question_9))) WHERE t1.APPLICATION = t2.APPLICATION;
I know you cannot update 2 tables in a single query so i tried this :
UPDATE reponse_question_finale t1
SET nb_question_repondu = (9-(COALESCE(t1.valeur_question_4,'')::int+COALESCE(t1.valeur_question_6,'')::int+COALESCE(t1.valeur_question_7)::int+COALESCE(t1.valeur_question_9,'')::int))
WHERE t1.APPLICATION = t1.APPLICATION;
But this query gaves me an error : invalid input syntax for integer: ""
I saw that the Postgres equivalent to MySQL is COALESCE() so i think i'm on the good way here.
I also know you cannot add varchar to varchar so i tried to cast it to integer to do that. I'm not sure if i casted it correctly with parenthesis at the good place and regarding to error maybe i cannot cast to int with coalesce.
Last thing, i can certainly do a co-related sub-select to update my two tables but i'm a little lost at this point.
The output must be an integer matching the number of questions answered to a backup survey.
Any thoughts?
Thanks.
coalesce() returns the first non-null value from the list supplied. So, if the column value is null the expression COALESCE(t1.valeur_question_4,'') returns an empty string and that's why you get the error.
But it seems you want something completely different: you want check if the column is null (or empty) and then subtract a value if it is to count the number of non-null columns.
To return 1 if a value is not null or 0 if it isn't you can use:
(nullif(valeur_question_4, '') is null)::int
nullif returns null if the first value equals the second. The IS NULL condition returns a boolean (something that MySQL doesn't have) and that can be cast to an integer (where false will be cast to 0 and true to 1)
So the whole expression should be:
nb_question_repondu = 9 - (
(nullif(t1.valeur_question_4,'') is null)::int
+ (nullif(t1.valeur_question_6,'') is null)::int
+ (nullif(t1.valeur_question_7,'') is null)::int
+ (nullif(t1.valeur_question_9,'') is null)::int
)
Another option is to unpivot the columns and do a select on them in a sub-select:
update reponse_question_finale
set nb_question_repondu = (select count(*)
from (
values
(valeur_question_4),
(valeur_question_6),
(valeur_question_7),
(valeur_question_9)
) as t(q)
where nullif(trim(q),'') is not null);
Adding more columns to be considered is quite easy then, as you just need to add a single line to the values() clause
when adding a new record like this
ContentContacts c2 = new ContentContacts();
c2.updated_user = c2.created_user = loggedUserId;
c2.created_date = c2.updated_date = DateTime.UtcNow;
db.ContentContacts.AddObject(c2);
I'm getting
Cannot insert the value NULL into column 'main_email_support', table 'SQL2008R2.dbo.ContentContacts'; column does not allow nulls. INSERT fails. The statement has been terminated.
but the default value in the database is an empty string like:
why am I getting such error? shouldn't the EF says something like:
"ohh, it's a nullvalue, so let's add the column default value instead"
I did a small test, created a table with a column that had a default value but did not allow nulls.
Then this SQL Statement:
INSERT INTO [Test].[dbo].[Table_1]
([TestText])
VALUES
(null)
Gives this error:
Msg 515, Level 16, State 2, Line 1
Cannot insert the value NULL into column 'TestText', table
'Test.dbo.Table_1'; column does not allow nulls. INSERT fails.
The problem here is that the insert specifies all the columns, also those with default values. The the Insert tries to update the columns with null values.
You have 2 options:
Update the table through a view, which does not contain the default columns
Set the default values in your C# code
A default value is business logic, so there is a case for it being set in the business layer of your application.