Questions tagged [null]
A database concept used to represent missing, unknown or inapplicable data.
0
votes
0answers
13 views
Pagination using seek-method with nullable columns, sharing a composite index with ORDER BY
I have the following table:
CREATE TABLE users(
id text PRIMARY KEY, -- actually a uuid
organization_id text NOT NULL,
lname text NOT NULL,
fname text NOT NULL
-- other irrelevant fields
);
...
9
votes
1answer
222 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
16 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
62 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 ...
0
votes
1answer
55 views
WHEN MATCHED clause fails if there's a NULL in the ON columns [duplicate]
I'm using a query with merge that works fine if all columns in the ON clause have a value but WHEN MATCHED omits if there's a NULL mark in one of the columns:
MERGE PEPS AS peps
USING (Lots of Cols..
...
1
vote
0answers
38 views
Should I Use Nulls/Blanks to Convey Meaning in a Related Column Representing a Category?
I'm designing a personal database that has a table which contains categories for seasonal events of a video game. In my design I have a related column from Events to Items (one to many [1:m] ...
1
vote
0answers
50 views
Allow Null Columns vs separate 1-to-many tables
Perhaps similar questions have been asked, but this is re having null columns.
I am too inexperienced to determine what would be the sounder way to approach the design of this database. Is it better ...
2
votes
1answer
95 views
Is there a function which the opposite of NULLIF?
I am aware of the NULLIF function which compares two values and returns NULL if they match.
Is there a function which will compare two values and return NULL if they don’t match? That is filter out ...
1
vote
2answers
27 views
Replace Null values with values from the same column by matching values in a different column
I have a table with some null values in column "date":
platform date id
---------------------------
web 2018-10-10 1
mob 1
mob 1
web ...
-2
votes
2answers
68 views
How to display null records/rows from table
For ex: I have a record with name = "sga_target", and no record exists where name = "_exafusion_enabled". I still want to display a row with "_exafusion_enabled" as name and NULL as value, without ...
0
votes
1answer
31 views
MySQL Varchar Primary Key With Not Null Constraint Accepting Nulls
I have the following table definition:
CREATE TABLE `invite` (
`id` varchar(255) CHARACTER SET utf8 NOT NULL,
`email` varchar(255) CHARACTER SET utf8 NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `...
1
vote
1answer
22 views
Why doesn't jsonb constructor from a NULL record behave like hstore constructor?
When I construct an hstore
CREATE EXTENSION hstore;
SELECT hstore(null::my_type);
hstore
------------------------------------------------
"name"=>NULL, "...
0
votes
1answer
27 views
IS NOT DISTINCT FROM vs row-wise equality with =
Looking at the below query,
SELECT null IS NOT DISTINCT FROM null AS indf,
null = null AS eq;
indf | eq
------+----
t |
From this we can see the result of the IS NOT DISTINCT FROM is true, ...
0
votes
1answer
56 views
Using NULL values for foreign key with normalization
I am creating a table as follows:
Building (PK: buildingID)
Area (PK: areaID, FK: buildingID)
Room (PK: roomID, FK: buildingID, FK: areaID)
All rooms are in a building. Some rooms can be in an area ...
1
vote
3answers
146 views
Returning 0 if value is NULL
SELECT
p.id
, ig.NumReceived
, og.NumShipped
, coalesce(
(p.StartingInventory - og.NumShipped + ig.NumReceived),
p.StartingInventory
) as OnHand
, p.ProductName
, p....
0
votes
3answers
37 views
Difference of two columns with possible NULL cells
I need to sort a table by the difference of two columns as
SELECT (first - second) AS dif
FROM table1
ORDER BY dif DESC
but the two columns can be NULL. In this case, it returns the error:
...
2
votes
3answers
89 views
Select the greatest value from each column, even if one of the values is null
I have a road_age_test table:
create table road_age_test (
surface_year int,
base_year int
);
insert into road_age_test (surface_year, base_year) values (10,20);
insert into road_age_test (...
1
vote
1answer
612 views
How to represent NULL in relational algebra?
In the 3rd part of the question below:
Study the tables given below and write relational algebra expressions for the queries that follow.
STUDENT(+ROLLNO, NAME, AGE, GENDER, ADDRESS, ADVISOR)
...
0
votes
1answer
942 views
Does PostgreSQL index null values? [closed]
If I have a table like so:
Food
-----------------
name | price | x
Let's say I create an index on name & price, but the database has a bunch of null values for both name & price in some of ...
6
votes
2answers
86 views
Deriving a computed column based on several nullable columns
I'm a bit of an SQL novice.
I've been trying to create an auto generated column called TAG from 5 other columns, some of which can retain NULL marks.
The syntax used to create the auto generated ...
2
votes
4answers
574 views
Can @parameter IS NULL slow down the execution of query?
Option 1:
CREATE PROCEDURE [dbo].[GetStudents]
@MinimumAge int = NULL
AS
select * from Students s where @MinimumAge is null or s.Age >= @MinimumAge
Option 2:
CREATE PROCEDURE [dbo].[GetStudents]...
5
votes
1answer
355 views
How to add a named constraint in Oracle SQL?
I have a table. I need to add a NOT NULL constraint to one of the columns. This is my best attempt at a solution:
alter table clookup add CONSTRAINT lookup_9 NOT NULL (clookup_col)
This produces ...
1
vote
1answer
182 views
SQL Query For Displaying 'No Data Found' for values containing null and 0 along with other records
The following was one of the practice questions in the online course i took on udemy for SQL.
I have a table 'emp' and consider the below names in the query map to their corresponding columns in ...
1
vote
0answers
249 views
Apache Phoenix Upsert not working while trying to update null/empty columns
Step 1: Update a column with null value.
Upsert into abc.tablename (Rowkeycombo1, Rowkeycombo2, columnname) values (123,to_date('1988-08-06'),null);
This works fine and the column then appears to ...
5
votes
1answer
658 views
SQL Server - Adding non-nullable column to existing table - SSDT Publishing
Due to business logic, we need a new column in a table that is critical to ensure is always populated. Updating existing references that insert/update is difficult but doable, but ensuring future code/...
-1
votes
1answer
18 views
Table for factory data along with user data
When creating master tables which are usually distinguished by a PK, say user_id, I'm often faced with the situation where I want to have a few pre-defined rows in the table.
I want data from these ...
-2
votes
1answer
48 views
HOW to work with NULL in a NOT NULL column?
I have a column that is specifyed as (int, not null).
I've been trying to insert NULL for the missing records of that column,
can anyone give me a hint?
0
votes
3answers
2k views
SQL left join returns null column [closed]
I am trying to do a LEFT JOIN on two tables, where one table has a datetime column, and the other table has a date column. As I am working in SQL Server, I used CONVERT to change the datetime to date. ...
3
votes
2answers
824 views
Count NULL values per row
I would like to count the number of null's present per row in a table without enumerating column names. For example:
WITH t as (VALUES
(NULL ,'hi',2,NULL,'null'),
('' ,'hi',2,3,'test'),
(NULL ,'...
1
vote
1answer
37 views
Not Null Fields and Unmatched Number of Columns
I am in charge of a task of migrating data from MySQL to PostgreSQL. I have already migrated the MySQL database to PostgreSQL with the help of pgloader. My problem is I need to insert the data from ...
5
votes
2answers
2k views
Conditional string concatenation in PostgreSQL
I have a table parcels which currently contains the columns owner_addr1, owner_addr2, owner_addr3. Sometimes, one or both of the latter two fields is empty. I want to combine them into a single new ...
1
vote
1answer
367 views
Transpose Rows to column
Can anyone Please help me to transpose below result
+------+------------+-------+
| SVR | dates | count |
+------+------------+-------+
| SRV1 | 03/25/2018 | 1 |
| SRV1 | 04/06/2018 | 59 ...
0
votes
2answers
726 views
COALESCE with cast
I'm pulling data from a jsonb column in Postgres, and casting it to an integer to compare it against a count. The problem is that in some cases the data apparently can't be cast to integer and I get:
...
0
votes
3answers
68 views
How to show a column as NULL if it doesn't exist in match?
I have a query as shown below.
In this query I am trying to get the result of orders which don't have messages (which I thought as null). But I was expecting that this query would produce a NULL in ...
0
votes
1answer
55 views
How to get 0 in the null value fields
select *
from
(
select type,SUM(ISNULL(amount,0)) AS amount,month(date) as date from tbl_cashmaster
where date between '2016/12/31' and '2017/12/31'
group by type,month(date)
) src
...
-1
votes
2answers
94 views
Sorting a Date Column in Microsoft SQL Server Management Studio
I have a table (master) with the following columns:
Order # (integer)
Location (varchar)
Est Start Date (date)
I want to return all rows. I want the rows sorted by Est Start Date, in ascending order,...
0
votes
1answer
263 views
Keep default value as 0.0 for 0 or NULL for numeric column
I have a numeric column Number(28,3) in which I have to insert value as 0.0 ,
whenever I encounter 0 or NULL/blank at the time of data insertion.
I have tried below :
NVL(col_name,0.0)
but it's ...
4
votes
2answers
668 views
SQL Server: specifying a unique optional column
SQL Server has a quirk with optional unique columns: you cannot have more than one null in a table.
For example:
create table employees (
id int identity(1,1) primary key,
givenname nvarchar(...
2
votes
0answers
82 views
Inserting two NULLs values into an UNIQUE column in SQLite
I use: sqlite-jdbc-3.21.0.jar
Error received:
SQLite_CONSTRAINT_UNIQUE] A UNIQUE constraint failed: companies.ncf
I ask a few things to the user, there is two fields that are optional to complete ...
6
votes
1answer
96 views
Join on NULL Key Column Optimizing as Table and Index Scans
I have a question about this query plan.
We have a table in a test environment, Order_Details_Taxes, that has 11,225,799 rows. This table has a column, OrdTax_PLTax_LoadDtl_Key, which is NULL on ...
1
vote
1answer
66 views
Firebird: table and null data
I'm working with Firebird database. I have a big table with many thousand of rows. Each line records the status of an object at regular intervals for many objects. I need to register new properties ...
4
votes
1answer
81 views
Why does PostgreSQL create an additional NULL bitmap if all fields after the 8th are NOT NULL?
I don't refer to the 1 Byte null bitmap included in the row header that could be used to flag null values for any of the first 8 columns. See:
https://stackoverflow.com/questions/12145772/do-...
1
vote
1answer
339 views
How to handle null value number DataWarehouse [duplicate]
I have a question.
I'm developing a Data Warehouse, I retrieve the data from my reconciled level, this in order to keep updated my Data Warehouse, but i am not sure how to handle some numeric fields ...
1
vote
3answers
142 views
Array to string sometimes concatenates fewer values
array_to_string(array_agg(array_to_string(array[
highlights,exceptions,inter_note,inter_status::text
,comp_note,comp_status::text,hard_note,hard_status::text]
,'|#|'::...
4
votes
1answer
34 views
Why does null and true evaluate to null but null or true evaluates to true?
Why does null and true evaluate to null in PostgreSQL but null or true evaluates to true?
I would have thought using null with and or or would've evaluated to null in both cases?
5
votes
2answers
104 views
Replacing NULL values with one string from provided list
I am trying to replace NULL values in table by using SELECT with one (randomized?) string from the set that I provide to the compiler.
Example:
|id | date |
+---+------+
| 1 | 2017 |
| 2 | NULL |...
1
vote
1answer
54 views
Having two entities that are the same except for 1 distinct attribute
In an example scenario for a database design assignment, a company provides hotel rooms (split into two entities - Hotel and Room) and apartments. So the database will contain the following entities:
...
3
votes
1answer
73 views
SSIS / SSAS: Handling Age Columns
I have some columns representing Age in a table, taking values from 0 to 100, but also -1 for 'Missing Value'. I don't want to store them as strings to be able to find average age etc., but SSAS turns ...
3
votes
1answer
534 views
SSIS - SSAS: Missing data handling
I have a solution in SSDT with a SSIS and a SSAS project, with missing values in both numeric and text columns.
Is it a good practice converting all the missing values of these columns to NULL during ...
5
votes
2answers
154 views
How to capture missing information in SQL Server tables
I have a few tables with nullable columns in a SQL Server database. Those nullable attributes are either not supplied at the time of row creation or they are not applicable in some cases.
I realized ...
