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

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Null Values and Performance

I always try to build the database avoiding any NULL values in my tables, and I have successfully had done this so far. (Hey, I am very new to database design.) But still there are times when saving ...
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3answers
3k views

Easier way to handle so many isnull() situation

Is there any good way to avoid writing so many times isnull() function inside sproc ? I have stored procedure that use almost 30 times isnull() function, I think that I am miss a concept , but until I ...
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2answers
569 views

MYSQL only Show columns which allow null

I need to be able to pull the column names which allow a NULL value, I know that show columns from TABLE Will give show me the table properties and whether or not the column allows null values, ...
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3answers
5k views

Select query to retrieve values even if are null

I need some help in a query. Need to retrieve data from 1 table, even if one of the field has null value. Here's an example: Select name, SUM(credit) as credit From expenses Where name like ...
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2answers
84 views

How to select data in the same table on different rows that are empty?

I use this select on my SQLite database: SELECT attributeX FROM table GROUP BY attributeX HAVING COUNT(attributeY) = 0; My table: attributeX (type integer) | attributeY (type text) ...
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1answer
582 views

How different clauses treat Null/Unknow in SQL Server 2012?

(relatively new to SQL and SQL Server) I am reading SQL Server 2012 T-SQL Fundamentals by Itzik Ben-Gan. Autor states that: SQL has different treatments for UNKNOWN in different language ...
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4answers
916 views

MySql Order by isnull() Performance Problem

my sql below is use for listing stock added from 10 days ago. Order by isnull(Price) is use so that stock without any price yet will still being listed. AddDate and Price has an index. SELECT Id, ...
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1answer
44 views

Pivoting with NULL Dates

I'm attempting the pivot below: SELECT EmpID as ID, [1] as January, [2] as February, [3] as March, [4] as April, [5] as May, [6] as June, [7] ...
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1answer
141 views

How can I insert records 'into null' in Oracle?

I'm looking for a way to insert records into a 'black hole'; i.e. execute a query for a certain table successfully, but make the records disappear. Something like INSERT INTO NULL, if you will. MySQL ...
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1answer
179 views

Alternatives to NULL for missing data [duplicate]

I am using PostgreSQL and trying to write value constraints. Is it possible to record missing data as distinct from NULL values in a numeric field without using an arbitrary numeric value? For many ...
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2answers
440 views

Expand sparse table with self outer join on distinct values

I have this: g1 | g2 | x ---------+-----------+----- New York | Monday | 210 New York | Tuesday | 258 Chicago | Monday | 30 Chicago | Wednesday | 25 LA | Thursday | 40 ...
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2answers
1k 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 ...
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1answer
78 views

What relevance does the table-level ANSI_NULL setting have?

Apparently, SQL Server stores the current ANSI_NULL setting when creating a table (see related questions here and here). However, when I execute SELECT * FROM myVeryOldTable WHERE ...
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1answer
543 views

Creating a partial unique constraint for MySQL

I have the same question as asked in a previous post: PostgreSQL multi-column unique constraint and NULL values. But the solution there is not applicable as I am using MySQL instead of PostgreSQL. My ...
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1answer
807 views

Conditional Where Statement Involving a NULL value?

Trying to find a way to pass off a third value within a 'bit' field. I would like to be able to utilize NULL as a searchable value. As in 'True', 'False', or 'NULL', the only issue is I'm unsure how ...
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1answer
1k views

How to change the display of an empty string in mysql command line tool?

I'm maintaining a database with InnoDB tables. These tables have some columns of type (from show create table): `val0` varchar(30) default NULL, `val1` varchar(30) default NULL, etc... From the ...
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1answer
26 views

always error “cannot insert value NULL” sqlserver

I want to update table "tmpiscunitmap.tr_kpi_id" year_period=2016 with value from table "tmp_kpi.tr_kpi_id where year_period=2016" with condition tmpiscunitmap.tr_kpi_id = tmp_kpi.tr_kpi_id on ...
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1answer
38 views

generate new column from another table column, treating nulls are unique

I have a table that looks like the following: |device_id | login_id | ----------------------- | 1 | NULL | | 2 | A | | 3 | A | | 4 ...
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1answer
34 views

cant order NULL value properly (mysql)

So I got this view in mysql : CREATE VIEW vote_question_totals AS SELECT question_id , SUM((vote_question_type)='1') question_total_plus , SUM((vote_question_type)='-1') question_total_minus , ...
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1answer
956 views

How to update where subquery value is null in SQL Server

I am attempting to update a column if another value from a subquery is less than a certain value or null: UPDATE Customer SET PriceClassID = 'A' FROM (SELECT custid, SUM(curybaldue) as last_sum FROM ...
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1answer
2k views

Query performance of a NULL vs an empty ('') varchar in SQL Server 2012

I have 3 indexed fields in a query: int, int, and varchar(250). The query performs well when all 3 conditions are specified with real values. The int columns always have values, but there are plenty ...
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1answer
140 views

Why is replication attempting to distribute NULL values into Identity columns

We are sporadically getting this error: Explicit value must be specified for identity column in our replication environment. I have checked the transaction command that is reporting the error and it ...
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0answers
18 views

Null Dimensions in SSAS [closed]

Several years ago 2008, I create a data warehouse using Business Objects. Business Objects did not process Outer Joins well and used SQL for all of its queries. Therefore, for every dimension I ...
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0answers
70 views

How to replace empty, multi-column result with single 'none'

If it is possible to make query in Oracle which will return single column/row with value "none" instead of empty, multi-column result? Otherwise return proper amount of columns with result. This is ...
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1answer
376 views

Populate one table with data from another one on selected cells

I have a problem with filling empty cells in one table with data from another one. I got a table with user emails - some of the fields are empty, some are already containing emails. I gathered the ...
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0answers
23 views

How do I include nulls during comparisons in SQLServer? [duplicate]

So basically in SQLServer a NULL means there is no value and thus can't be compared which returns some unexpected results. For example, the following query doesn't return rows where value IS NULL but ...
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1answer
334 views

Database Normalization: A Case Of The NULLs [duplicate]

I'm trying to learn about proper database management and am having a hard time with designing a database that doesn't rely on NULLs. If you think I'm crazy for embarking on this, it is because of SQL ...
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0answers
104 views

How to merge rows based on how much data they have?

I am cleaning data and I formed a table something like this: file | product | color | product_id --------------------------------------------- one.csv pipe blue null ...
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0answers
81 views

Dealing with null values in non-nullable columns in a NoSQL database

If I have an existing table in a NoSQL database cluster and I want to add a new column that should never return null, how do I handle it in my application code? I can update all exist records and ...
0
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1answer
95 views

SQL Server's aggregate functions ignore nulls. How do I correct this?

According to MS's knowledgebase, Except for COUNT, aggregate functions ignore null values. Does anyone know how I can get it to work correctly, that is, return a null if it attempts to ...
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2answers
739 views

Is where x = 0 or x is null to be replaced by where isnull(x, 0) = 0 resp. where NVL(x, 0) = 0

Think of x as a column containing null, 0, 1. Only less than 1 % of the rows contain 1. There is no logical difference between 0 and Null. Is it a good idea to insist, that isnull rather than NVL is ...
0
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1answer
294 views

sql-server optimize query with lots of null checks

I have a query such as: select something from somewhere join stuff on condition join more_stuff on condition where somewhere.sometime is null and somewhere.someone is null and stuff.whatever is null ...
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3answers
852 views

Two nullable columns one required to have value

No-Explanation Question: Is there anyway to have a constrain of 2 null values that always requires 1 to have value ? For example two date columns both null but having at least 1 that requires to have ...
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2answers
164 views

oracle null value in quotes - yet another newbie question

I have a where clause like "and uc.completion_status in ('[P....]') " here ('[P....]') is the user input from taken a dropdown list in the user interface. and dropdown list consists three options ...
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2answers
21 views

How to get the second string in the ORA-02296 error to show something meaningful

Whenever I run the following script*: ALTER TABLE ANIMAL.MONKEY MODIFY TAIL_COUNT NOT NULL; I receive the following error: ORA-02296: cannot enable (ANIMAL.) - null values found I have a ...
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1answer
328 views

TSQL change column constraint between null and not null

I am doing a exercise to change a column's constraint between null to not null. Table name: Production.categoriesTest. Please review my question and give me suggestion on what I did wrong and how to ...
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1answer
5k views

WITH ROLLUP WHERE x IS NULL

I tried to find this question somewhere else on here, and found a couple that were similar to it -- but all the answers seemed pretty convoluted, and I think it was surprising to me because I just ...
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1answer
17 views

How to prevent #Error values derived from Nulls in an outer join

Suppose I have two tables to outer join Tab1: ID Nam 1 Joe 2 Moe 3 Flo Tab2: ID Val y w 1 stuff 66 33 2 duff 67 44 and one of the resulting columns is derived -- i.e., ...
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2answers
288 views

mysql UNIQUE KEY multiple columns with one column as NULL

I understand the way UNIQUE KEY works in Mysql 5.5+, and understand that NULL allows duplicate entries to be created. In following schema and I would finally want that family_relation should have ...
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2answers
315 views

insert inserted id to another table

Here's the scenario: create table a ( id serial primary key, val text ); create table b ( id serial primary key, a_id integer references a(id) ); create rule a_inserted as on insert to a do ...
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1answer
38 views

multi-column FKs with NULL values

I understand that in PostgreSQL if there is a multi-column FK from table B to table A and one or more of the FK columns in table B are nullable then the FK is still considered as "honored" for the ...
0
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1answer
34 views

Dealing with co-dependent not null columns

Say I have a table entities (subclassed by people and organizations tables), where each entry requires a primary_email_id. The entities table looks like this: entities ======== id INT AUTO_INCREMENT ...
0
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1answer
517 views

Return a default value in group by if selected column is null

I am trying to run a group by statement which works fine however, one of the "group" is null. How do I return "Unknown" for that row? For example: 10000 A 9999 B 9990 C 4 etc. First ...
0
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1answer
624 views

MySQL warnings while loading integer data into table (SOLVED)

For some reason, after loading a large amount of data into the following table (from a single file), all of the values register as 0. CREATE TABLE secondTable ( freq int NULL, w1 int NULL, w2 int ...
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1answer
1k views

Find ID columns with null value in oracle database

I need a way to iterate through all tables in tablespace "T_ECOS" and find all ID with null value in oracle database Any suggestion?
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0answers
27 views

Postgresql indexing for IS NULL

I have two similar queries, whose only difference (in the last two lines) is that one uses IS NULL while the other compares defined values. Query #1 takes only a few minutes: UPDATE ...
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1answer
36 views

Filling not applicable fields with N/A rather than leaving them empty or Null [duplicate]

I have a database of few million records, many of the fields (call them Ec1 to EcN) have either Null or empty string in them. When I looked at them more closely, I found that for many records, several ...
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1answer
88 views

LEFT JOIN DEFAULT NULL VALUE

I had query simplified like this : SELECT a.id, a.name, b.* FROM a LEFT JOIN b ON a.id=b.id Which b is from group concat select (very dynamic column). Sometime there are 3 column in b, sometime ...
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0answers
54 views

Null in Varchar datatype

I am using a SQL Server database. If NULL value is inserted to a VARCHAR datatype column, what will be the memory size used for the column?
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1answer
288 views

MySQL is inserting “” as 0 in decimal fields. How to stop that?

The fields are nullable, so they do allow nulls. Why would MySQL convert "" to 0 instead of NULL? Is there a way to force it to be NULL instead?