Tagged Questions
2
votes
1answer
90 views
Update “NULL” string to Actual NULL value
I have a table that contains NULL values but the problem is that some of the values are actually string "NULL" and not actual NULLS so when you trying something like
where date is null
it will not ...
1
vote
2answers
122 views
Only one NULL for one part of primary key
I have two date columns : "start date" and "finish date".
I want to make sure that there can be only one null value in the "finish date" column (which should be current state if it's NULL) for one ...
12
votes
3answers
769 views
Why does ANSI SQL define SUM(no rows) as NULL?
The ANSI SQL standard defines (chapter 6.5, set function specification) the following behaviour for aggregate functions on empty result sets:
COUNT(...) = 0
AVG(...) = NULL
MIN(...) = NULL
MAX(...) = ...
4
votes
2answers
134 views
Checking a wide table for nulls [duplicate]
Possible Duplicate:
Test if any fields are NULL
I am new here. I have a table with 70-odd columns. Is there a way I can check the number of rows with at least one null value in any column ...
9
votes
1answer
382 views
Why does NOT IN with a set containing NULL always return FALSE/NULL?
I had a query (for Postgres and Informix) with a NOT IN clause containing a subquery that in some cases returned NULL values, causing that clause (and the entire query) to fail to return anything.
...
4
votes
1answer
169 views
Adding SPARSE made table much bigger
I have a generic log table, about 5m rows.
There's a "strongly typed" field that stores event type, and a bunch of "losely typed" columns that contain data relevant to the event. That is, meaning of ...
5
votes
7answers
559 views
Database table and NULLs
I know that there have been many opinions/sides concerning NULL values in a database.
I have not understood though what is the best practice for this.
I.e. if I have a relational table with an ...
9
votes
3answers
4k views
PostgreSQL multi-column unique constraint and NULL values
I have a table like the following:
create table my_table (
id int8 not null,
id_A int8 not null,
id_B int8 not null,
id_C int8 null,
constraint pk_my_table primary key (id),
constraint ...
3
votes
0answers
259 views
To NULL or not to NULL? [duplicate]
Possible Duplicate:
Why shouldn't we allow NULLs?
I've heard that it's a bad idea to do database design such that nullable fields exist. However, eliminating nullables often cause much ...
1
vote
2answers
430 views
null check and string concatenation
Can I do better than this query?
select func_returns_str('key1') ||
nvl2( func_returns_str('key2'),
',' || func_returns_str('key2'),
null)
from dual;
I ...
3
votes
2answers
827 views
PostgreSQL: count datasets / lines containing NULL values
I'm looking for a easy function to get the number of datasets (of any table) containing NULL values. It's not important how many columns are involved.
For example:
CREATE TABLE tab1 (
id INTEGER ...
35
votes
4answers
5k views
What is the difference between select count(*) and select count(any_non_null_column)?
I seem to remember that (on Oracle) there is a difference between uttering select count(*) from any_table and select count(any_non_null_column) from any_table.
What are the differences between these ...
