Questions tagged [null]

A database concept used to represent missing, unknown or inapplicable data.

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2answers
192 views

MySQL best way to define a couple of columns as both null or both not-null

On a MySQL DB, I would like to find a way to force a couple of columns be both null or both not null at the insert / update time. This means that on each record, both columns are null or both columns ...
1
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1answer
16 views

Mysql update table from another table with condition

In mysql i have 2 table. First wp_postmeta_import Second wp_postmeta_temp These tables have these columns: meta_id post_id meta_key meta_value I need to update only my column meta_value of ...
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2answers
44 views

Using a NULL value to signify that the value does not mattter. Not that it isn't known [closed]

Say I have a table with computers where one column is a boolean "fan". If true the computer has a fan, if false it does not. It can never be null. Now I have another table with a list of ...
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2answers
70 views

How to allow NULL in foreign keys of a compound primary key

I want to have NULLs in foreign keys of a compound primary key. This is an example of what I would expect to be valid data. product_id variant_id 123-123 ABC 123-123 NULL 456-456 ABC I cannot ...
1
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2answers
41 views

EAV - COUNT()/SUM() on column and row values with and without NULLs

Assume that there is a table demo with these data: id userID title data 1 1 DATE 01-01-2021 2 1 COLOR RED 3 2 DATE 4 2 COLOR YELLOW 5 3 DATE 04-01-2021 6 3 COLOR RED 5 4 DATE 04-01-2021 6 4 ...
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1answer
21 views

Displaying null fields as 0 in mySQL select [duplicate]

I have a database that collects statistics from Usenet. When I do a basic select such as: select day, count(day) from statistics where month = 12 and year = 2020 group by day; I get the result +------+...
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3answers
214 views

Function: if either x or y are null, return null

I'm looking for an Oracle 18c function that evaluates to null if either of two variables is null. The Constraints: (details here) The function/expression can't contain spaces (so CASE won't work). I ...
2
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1answer
67 views

Find tables with columns with empty and NULL values in Postgresql

After some research I found an example where I can find tables and its columns with NULL values. But the function also returns true when the column is empty. It gives me errors when I try to add an or ...
2
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1answer
42 views

PostgreSQL's record type returning null?

I don't understand why this result is possible. Can someone explain why the first assert returns true and the second false? generate_token() is a function that generates a random bytea and inserts it ...
0
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0answers
36 views

Disallow empty strings in text columns (Aurora / PostgreSQL)

We have a Django application connected to an Oracle database running in production and we are planning to create a new instance on AWS. Both instances would coexist. On AWS we would like to use Aurora ...
-1
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1answer
645 views

How to set default value as empty string for all rows at once in MySQL while creating the table

In MySQL, while creating a table, I'like to have empty string '' as value for all needed columns instead of 'NULL'. Is it possible, is it safe and how can I do to do that at once? I have the following ...
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1answer
59 views

Get records where no column is null [duplicate]

I've a table with 100+ (nullable) columns and 10,000+ rows. I'd like to fetch rows that have no columns null. id|f001|f002|f003|....f100 1 |null|aa | ss |sada 2 |sdad|aa | ss |sada 3 |as |aa | ss |...
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1answer
28 views

Replacing Null value with existing value

How would it be possible to replace the null value from Order - column with the above existing value that has the the same Document-number? Document Value Value2 Order 1234567 4 7 ...
2
votes
2answers
194 views

Count missing values in each column of the table in PostgreSQL

Question: Which column of fortune500 (a table) has the most missing values? To find out, I have checked each column individually mentioned below, which is very tedious. SELECT SUM(CASE WHEN ...
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votes
1answer
20 views

Nullable integer as part of composite primary key

I want to store phone numbers as integers and I've created this SQL: DROP TABLE `user_id_phone`; CREATE TABLE `user_id_phone` ( `user_id` int unsigned NOT NULL, `country_code` ...
0
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1answer
113 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
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1answer
44 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
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1answer
412 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
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1answer
1k 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
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2answers
519 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),...
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0answers
70 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 ...
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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 =...
5
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2answers
507 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
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2answers
23 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
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3answers
52 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
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1answer
138 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
51 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
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0answers
14 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
76 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
554 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
285 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 ...
1
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0answers
46 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
144 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
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2answers
25 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
224 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
85 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 ...
-1
votes
1answer
68 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
38 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
24 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
297 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
327 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
46 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 ...
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votes
1answer
30 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
1answer
88 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
719 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
777 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
257 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
499 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 ...

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