Questions tagged [null]
A database concept used to represent missing, unknown or inapplicable data.
298
questions
0
votes
1answer
50 views
What is the best way to store optional values in table?
I have a large table that will be partitioned (about 300 million rows). There are currently 57 columns in the table. At the moment we also have an 'Option' column, which is to hold values that would ...
-3
votes
1answer
42 views
Why am I getting errors which cannot logically happen? [duplicate]
I'm ready for the nuthouse at this point. This error makes me want to stab my eyes out after staring at the screen and testing stuff for literally MONTHS now!
The offending code, which looks to me ...
0
votes
1answer
23 views
Postgres 11 - Range Partitioning on a Date Column with NULL values
We have a table structure with parent and child records inside the same table. They are referenced via a column (parentId) which references the parent (and null on the top parent records). Also, we ...
0
votes
1answer
73 views
Testing a Hive array for IS NULL says not null
I have a table containing an array, and I want to check if it is empty or NULL. It appears that I cannot check the NULL directly! Can anyone shed light on why the NULL check isn't working?
create ...
1
vote
2answers
52 views
Why does my SELECT query not return null values? [duplicate]
I have the following SQL script:
CREATE temporary table if not EXISTS the_values (
key SERIAL,
value INTEGER NULL
);
insert into the_values(value) values (null),(1),(null),(2),(3),(4),(5),(6),(10),...
0
votes
0answers
24 views
MySql view returns a single NULL value for a NOT NULL column, why?
I am working with a database built by a vendor, which I have remote access to. I noticed that the field modify_date on one of the views is not null, according to DBeaver.
the tick indicates "not ...
-1
votes
1answer
45 views
Joining 3 tables together and selecting the null elements without using is not null [closed]
select Name from Passagerare
left join EB
on Passagerare.Personnr = EB.Personnr
left join MM
on Passagerare.Personnr = MM.Personnr
where Passagerare.Personnr = EB.Personnr or Passagerare.Personnr =...
4
votes
2answers
159 views
How can I set a column to NOT NULL without locking the table during a table scan?
(former question was: Will Postgres use a multi-column index when setting multiple colums not null?)
Typically, when I set a column not null, if it doesn't have an index then I add it first, so that ...
0
votes
2answers
20 views
How to check if staff member has end date with a Null value
I have a database that records employees tasks throughout the organisation and when they finish etc., I need to identify if each employee, has at least one row with a null value in either finish.
...
0
votes
3answers
51 views
Problem with IF statement [closed]
I am having an issue with this stored procedure. When the user selects "Yes", it should do what it says in the if statement for the "Yes" but it does not do anything, it does not insert anything into ...
0
votes
1answer
39 views
JOIN/Union Two tables, removing NULL where possible (similar to pandas concatenate)
I am wondering how to perform an operation that I guess is most akin to a concatenate if you're familiar with pandas.
Basically, what I want to do seems like a UNION where records are "collapsed" in ...
1
vote
2answers
46 views
Should fields that are set to Not Null also have a constraint refusing empty strings?
Any field that I would expect a value (Like an orderNumber or customerNumber) I would set as not nullable.
If I'm expecting the value of the field to be not null, shouldn't I also always have a ...
0
votes
0answers
12 views
What is the commonly-accepted practice to denote the different meaning of NULLs?
I am thinking about what's the meaning of NULL in my database systems. In some columns it mean unknown / missing data. In some columns it mean a not-applicable field. In some columns it mean the ...
1
vote
1answer
27 views
In SQL Server, for numeric data type, can the CHARACTER_MAXIMUM_LENGTH be different from NULL?
I have a SQL Server with numeric types for few columns.
When getting a table structure, I have the following results:
Query:
SELECT *
FROM DB.INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = '...
0
votes
1answer
59 views
How to remove NULL values in multidimensional array?
SELECT dt.name,dt.description,dt.odobj,dt.defval,dt.datatypeid
,array_agg(array[dtv.description::text,dtv.odobj::text,dtv.name::text,dtv.datatypevalueid::text,dtv.datatypeid::text]) as ...
4
votes
2answers
283 views
Why is the result of a totally deterministic and all-encompassing “case” in select query in view nullable?
I have a table, with Id as the primary key.
create table Anything
(
Id bigint not null primary key identity(1, 1)
)
When I look at this table in Object Explorer, I see this image of course:
As ...
0
votes
0answers
18 views
How to get latest record of partition when Field1 & Field2 is not null or get latest record where one is null and 2nd latest where same field isn't?
Hard question to verbalize in the title with character constraint, sorry.
I have Table1 with the fields PartitionField, ImportantField1, ImportantField2, DateField.
ImportantField1 or ImportantField2 ...
1
vote
0answers
29 views
Why does PostgreSQL explicitly cast NULL to parameter data type in functions?
Let's say I create the following function:
create or replace function my_new_function(
p_something text default null
)
etc....
But if I go to check the function on PostgreSQL I see this instead:
...
2
votes
1answer
33 views
How to filter table 2 before joining to table 1 so that the result still includes all of table 1, even if no match in table 2?
The following returns all rows from table 1 where post_type = dlm_download. It groups like values from table 2 by the matching column in table 1 so that each row in table 1 has a maximum of one ...
1
vote
1answer
79 views
Database Design: Normalization and NULL values
I have normalized my table from 0NF to 2NF (hopefully correct).
How do I now go from 2NF to 3NF?
Also, ResponseToTransactionId is a recursive foreign key that will contain NULL values a lot of the ...
0
votes
2answers
17 views
Is there any way to force at least one column NOT NULL
I have a schedule_days table that is having id, day, date columns.
id - auto increment, primary key
day - weekday - enum(weekdays) default not null
date - a specific date - default not null
...
-2
votes
1answer
136 views
Working with NULL Date Fields [closed]
I have a derived VARCHAR date field that I need to use for deriving another field, based off of whether or not the date field has a value. The derived date field is called "AmortDate" and I'm ...
1
vote
3answers
74 views
NULL as a @variable within WHERE clasue
I would like to SET 'IS NULL' as a variable and use it in a WHERE clause.
I will be unioning many tables together that carry the same WHERE clause and would like flexibility to use a variable for my ...
0
votes
1answer
57 views
Column values in SQL Server changes to null [closed]
There is one specific column whose value automatically changes to null after data is inserted into it.
I have tried to update the column from designer, update the column with query, delete the ...
1
vote
1answer
32 views
Null check condition in Where clause
DECLARE @SubDesc1 nvarchar(100)
SET @SubDesc1 = null
I would like to do something like that.
Query 1
SELECT *
From Table1
where Category = 'Category1'
AND [Description] ='ABC'
AND ...
0
votes
2answers
23 views
Work around average behaviour with nulls
I have two tables:
Product (PK product_id, brand, model)
Order (PK invoice_id, customer_name, customer_email, FK product_id)
I am trying to find the product(s) whose number of times that product is ...
6
votes
1answer
145 views
Why does ORDER BY NULLS LAST affect the query plan on a primary key?
Using PostgreSQL 11, I have the following table with around 450 million rows:
postgres=> \d+ sales
Table "public.sales"
...
-1
votes
1answer
60 views
Can't get this query to work properly
I've been trying to get the following query working for days but I can't seem to solve my issue. I'm using the MySQL version 5.7.9
I have the following database:
CREATE TABLE user (
id INT NOT ...
1
vote
2answers
191 views
How to filter hstore where values are not null in a trigger?
The easiest way to explain the question is in the usage of an audit trigger.
However, on insert it saves all values, including null values. I want to filter out the null values in the hstore(NEW.*). ...
2
votes
2answers
38 views
NULL rows and IS NULL
I've been writing some queries that look like this:
SELECT
...
FROM table_a a
LEFT JOIN table_b b
ON b.id = a.id
LEFT JOIN table_c c
ON c.id = a.id
In these queries only one of the joins can ...
-1
votes
1answer
21 views
null value in postgres functions
I am new in postgres and i found this issue with this simple function
CREATE OR REPLACE FUNCTION "public"."TEST"("disponibile" int2=0, "extra" int2=0, "ordini" int2=0, "prenotata" int2=0)
RETURNS "...
2
votes
0answers
56 views
Oracle DISTINCT with NULLable columns
There is a longstanding(?) problem(?) with Oracle that if you want to use a DISTINCT select on a column which has a B*-Tree Index but is nullable, that the index is not used. (As other answers suggest,...
1
vote
3answers
282 views
Take average of multiple nullable columns
I have an example table (year) as below in PostgreSQL 9.5:
Name | 2010 | 2011 | 2012
-------------------------
A | 10 | | 40
B | 10 | 20 | 30
Now, if I write a simple query as ...
6
votes
2answers
609 views
NULL value causes blank row in SELECT results for text concatenation
I have a query for producing some text for creating some VALUES text to put in a .sql file for inserting some rows. I get a blank line in the results:
postgres=# SELECT ' (' || obj_id || ', ''' || ...
3
votes
2answers
154 views
How to understand “NULL NOT IN” when the set is empty?
The SQL in this question is for Oracle. But you can simply remove FROM dual to make it work on SQL Server (which returns the same result as Oracle).
I have the following SQL:
SELECT 1
FROM dual
...
7
votes
1answer
427 views
Multiple BIT datatype columns in the same table
Consider the following information coming from Microsoft SQL docs pages:
The SQL Server Database Engine optimizes storage of bit columns. If
there are 8 or fewer bit columns in a table, the ...
1
vote
1answer
44 views
Why null is getting compared with null in the join condition in SQL Server 2016?
It's a simple self join I am trying to do on below data
and the O/P I am getting after running following query (This is not the complete output, just showing the null part of it)
select a.col1, a....
12
votes
3answers
817 views
Increase speed altering column on large table to NON NULL
I recently added a NULL-able bit column to a table which has close to 500 million rows. There's not a default on the column, however all inserts are specifying a value of 0 or 1, and I ran a one-time ...
1
vote
2answers
1k views
MySQL 8.0 cannot insert NULL values to date field
I'm trying to insert a data from file to MYSQL 8.0 using the InnoDB engine.
I'm using this query:
LOAD DATA INFILE '/var/lib/mysql-files/item_new_1_4.dat'
INTO TABLE Item FIELDS TERMINATED BY '|';
...
0
votes
1answer
53 views
Comparing nullable column values using “IS NULL” versus “= NULL”
I'm dealing with nullable values in a column of a table, i'm wondering why this:
with cte as (
select 'c1'::text as c1,null::text as c2
union
select 'c2'::text as c1,null::text as c2
)
...
1
vote
1answer
2k views
LEFT JOIN and handling NULL Values [closed]
I have two tables.
Table 1:
A B
------
1 'A'
2 'B'
3 'C'
Table 2:
A C
----------
2 15
3 20
I'm using the following query:
SELECT table1.A, table1.B, table2.C
FROM table1
...
0
votes
3answers
153 views
MySQL, IF statement, variables, and NULL
After struggling for too long with something that should have been simple, I had a question to ask, but while writing it, I kept looking for solutions and I finally found the solution. I am posting it ...
-1
votes
1answer
53 views
Replace NULLs with value
Here is my temporary table:
CREATE TABLE #test123(
c1 float,
c2 float,
c3 float,
c4 float,
c5 float
);
INSERT #test123(c1,c2,c3,c4,c5)
VALUES (2,3,NULL,1,2),
(2,NULL,NULL,...
14
votes
3answers
4k views
How to get the last not-null value in an ordered column of a huge table?
I have the following input:
id | value
----+-------
1 | 136
2 | NULL
3 | 650
4 | NULL
5 | NULL
6 | NULL
7 | 954
8 | NULL
9 | 104
10 | NULL
I expect the following ...
asked Mar 31 '19 at 17:19
peterh - Reinstate Monica
1,6235 gold badges20 silver badges35 bronze badges
2
votes
2answers
413 views
How can the concatenatation of a text and a NULL value return a non-null result?
Assert 1
The concatenation operator || can concatenate any string type values, returning text. In Postgres, every type has a text representation and can be cast to text. Consequently, quoting the ...
0
votes
1answer
124 views
Display all fields with null values in a particular row in SQL Server
I have a requirement where I want to fetch and display all the fields with NULL value for a particular row in the table.
Some thing like:
select 'all columns with NULL'
from table_xyz
where ...
2
votes
1answer
348 views
Conditional ORDER BY based on NULL values in the column
I have a table like this.
table(student_name nvarchar(20) not NULL, grades int).
When I write
select * from table
order by grades asc
It shows this
student_name | grades
---------------------
...
10
votes
1answer
3k views
Why do I need to cast NULL to column type?
I've got a helper that's generating some code to do bulk updates for me and generates SQL that looks like this:
(Both the active and core fields are of type boolean)
UPDATE fields as t set "active" =...
0
votes
3answers
20 views
MYSQL: Display NULL value when foreing key is NULL
I have the following database structure in MYSQL:
CREATE TABLE xs_bugtracking (
`id` INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
`product` VARCHAR(64) NOT ...
2
votes
1answer
1k views
PostgreSQL performance with (col = value or col is NULL)
This question deals with PostgreSQL 9.5 query performance.
The table is:
CREATE TABLE big_table
(
id integer NOT NULL,
flag bigint NOT NULL,
time timestamp with timezone NOT NULL,
val ...
