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

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1answer
16 views

Alter TEXT column to NOT NULL when there is existing NULL rows

Mysql does not support default values for TEXT columns. I have a live database with NULL values What is the proper way to change all null values to a predefined value and change the column to not ...
-4
votes
0answers
24 views

How to populate a value into the null value of two duplicate records, one with some value and the other with the null [closed]

Data: Accnt No: | Trans_id| Amount| Remarks XXXXXXX100 | 501 | 100 | successful XXXXXXX102 | 503 | 5000 | successful XXXXXXX102 | 503 | | successful XXXXXXX103 | 505 | ...
0
votes
2answers
33 views

General Database Optimizations - correct data types - why to avoid NULL? [closed]

Oracle recommends: Choose the correct data types and size to: – Avoid NULLs – Improve performance – Protect data – Use data compression where appropriate I don't understand why I need to avoid ...
77
votes
7answers
20k views

Why shouldn't we allow NULLs?

I remember reading this one article about database design and I also remember it said you should have field properties of NOT NULL. I don't remember why this was the case though. All I can seem to ...
0
votes
3answers
44 views

What data type for a column which can have three states: yes, no, unknown

I have an application where the user can decide between: yes no unknown I started to use a boolean column which is nullable. But things get quite complicated since my framework (django) does not ...
2
votes
1answer
38 views

Using GROUP BY WITH ROLLUP on column that contains NULL

I have the following table (see it on SQL Fiddle) (I created to break down my problem): | ID | word | ---------------- | 5 | "Hello" | | 6 | NULL | | 7 | "World" | | 8 | "World" | Now I ...
-1
votes
0answers
27 views

View NULLABLE Column Issue

I have a View that contains a column from a base table. The column is set to NOT NULL in the base table. However, in the view it is set as NULL. Even if I mouse over the CREATE VIEW script it shows ...
2
votes
5answers
130 views

How can I allow part of a key to be null and enforce uniqueness of records with nulls?

I have an Access table called Engagement with four fields: Emp_id, Year, Week, Act_id It records when an employee is/was engaged in an activity. Each field is Number and each makes up part of the ...
11
votes
3answers
5k views

Comparing Columns that can contain NULLS - is there a more elegant way?

I know that you can't compare a value to NULL and expect a result without adding something like in the following code... SELECT * FROM A INNER JOIN B ON A.ID = B.ID WHERE A.STRING &...
0
votes
0answers
44 views

Simplifying this NULL check [duplicate]

Is there a way to simplify this check? I would like to compare if two columns are equal and that includes if one is NULL and the other has a value (which would mean they're considered different). (A.[...
0
votes
1answer
18 views

Where clause returns null, but need to return 0

Need an SQL Statement for the following: Table a partID partNumber Table b partID purchased SELECT a.partNumber FROM a WHERE (SELECT SUM(b.purchased) WHERE b.partID=a.partID) > 0 If ...
1
vote
1answer
49 views

Distinguish between unknown and non-present foreign keys

I'm in the situation of importing data from multiple other applications. The data is stored in multiple tables that contain foreign keys. Some of these applications don't provide all the needed data ...
-3
votes
2answers
77 views

Case statement by using IsNull and IsNotNull [closed]

ALTER FUNCTION [dbo].[addC]() RETURNS varchar(255) AS BEGIN DECLARE @desc varchar(255); DECLARE @desc1 varchar(255); SET @desc = '' SET @desc1 = '' Declare c1 Cursor for ...
2
votes
3answers
86 views

Full Outer Join shows NULL when Group By is used

I have 4 subqueries and each of the subquery is grouped by 'Group name'. The attempt is to have each subquery as a column all grouped by the 'Group Name'. Here is the query: select coalesce(co....
4
votes
2answers
337 views

How do I order by NULLS LAST if my database doesn't support it?

Select FullName, Login FROM [User] ORDER BY FullName desc, login asc Results FullName Login ----------------------------- ------------------------------ M...... ...
7
votes
2answers
146 views

What are the consequences of not specifying NOT NULL in PostgreSQL for fields which can't be null?

I have an application (data is stored in PostgreSQL), where majority of the fields in the tables are always not null, but the schema for these tables does not enforce this. For example look at this ...
3
votes
2answers
79 views

Enforce uniqueness across optional attributes for an entity

I have an entity that has multiple attributes, and these attributes are themselves entities. No two entities may have the same attributes, so there needs to be a uniqueness constraint across them. ...
0
votes
2answers
37 views

Compare possible null values in one query

Question is pretty short and simple: I have following query: SELECT * FROM CTE Now I want to get all rows with only maximum value of some field. SELECT * FROM CTE WHERE NodeId = (SELECT MAX(...
1
vote
2answers
39 views

MySQL stored procedure returns null

I wrote a simple procedure to modify the whole column to a set of meaningless values. However, when I tried call NewProc('tableName','colName') it returned 1064 - You have an error in your SQL ...
5
votes
2answers
117 views

Need help with null field values

I am having a problem with syntax. I have the following statement which updates a field in a table with a value from a field in a different table. I need the statement to update the field with the ...
52
votes
7answers
14k views

If a person's name is Null then how would it break the database?

I was reading this article on BBC. It tells a story of a person named Jenifer Null and how she faces day to day problems while using online databases like booking plane tickets, net banking etc. I am ...
12
votes
3answers
697 views

Can IS DISTINCT FROM be combined with ANY or ALL somehow?

Is a postgres way of combining IS DISTINCT FROM with ANY or some other neat way of getting the same result? select count(*) from (select 'A' foo union all select 'Z' union all select null) z where ...
1
vote
3answers
185 views

Finding count of null values in 500 columns of a single table

I have 500 columns in a table in SQL Server. I want to find the count of null values in each column. Is there a way to do it using a cursor and dynamic SQL?
44
votes
5answers
32k views

Why does ALTER COLUMN to NOT NULL cause massive log file growth?

I have a table with 64m rows taking 4.3 GB on disk for its data. Each row is about 30 bytes of integer columns, plus a variable NVARCHAR(255) column for text. I added a a NULLABLE column with data-...
4
votes
2answers
2k views

Are many NULL columns harmful in mysql InnoDB?

As I explored the clustered B-tree index system of InnoDB, I think that the presence of many NULL (or small) columns has no significant effect on InnoDB performance. Does the presence of excess ...
6
votes
1answer
456 views

SQL Server Left Join strange NULL check

I've just been going through some old stored procedures, doing some optimizations and stumbled across this oddity: SELECT ISNULL(bt.BusinessTypeID, 0) AS BusinessTypeID FROM BusinessType bt LEFT JOIN ...
0
votes
2answers
72 views

How to omit multiple columns where is not null?

I've constructed the below query which satisfies the requirements, except output includes NULL values between all "vendor_address2" columns, which isn't intended. I suspect my error is somewhere ...
5
votes
3answers
6k views

Count null and not null values in a column

How to count and retrieve null and not null on same column in MySQL? mytable --------------------------------------------------- id | name | visited | registDate | ------------------...
0
votes
0answers
57 views

Comparisons with NULL values and not using ISNULL function

Hello and thank you in advance. My question is that with ansi-nulls on, how can I do a proper comparison between two fields without using an isnull function (or coalesce)? For example the following ...
0
votes
4answers
4k views

ISNULL() OR Is NULL in UPDATE statement

I have to run an UPDATE statement on live online database with about 5 lac records. I want to know which statement will run faster: Update Table set REC_ID = isnull(REC_ID,'') Update Table set ...
8
votes
4answers
43k views

Getting SELECT to return a constant value even if zero rows match

Consider this select statement: SELECT *, 1 AS query_id FROM players WHERE username='foobar'; It returns the column query_id with value 1 along with a player's other columns. How would ...
4
votes
5answers
978 views

Enforce NOT NULL for set of columns with a CHECK constraint only for new rows

I have a table and need to add a new column without a default value: Constraint: ALTER TABLE integrations.billables DROP CONSTRAINT IF EXISTS cc_at_least_one_mapping_needed_billables, ADD ...
8
votes
2answers
13k views

How do I check for a null or empty table-valued parameter?

I have a stored procedure (SS2k8) with a couple table-valued parameters that will sometimes be null or empty. I have seen this StackOverflow post that says that null/empty TVPs should simply be ...
3
votes
2answers
948 views

Using sp_BlitzIndex - Diagnosed as “Index Hoarder: Addicted to nulls”

Context: MS SQL Server 2012 In using Kendra Little's awesome tool, sp_BlitzIndex, a number of tables were diagnosed as "Index Hoarder: Addicted to nulls". I'm not looking for a debate over NULLs and ...
2
votes
4answers
5k views

Null Or Multiple Parameters When Querying

I have a stored procedure that has a parameter that must take a comma delimited varchar list of values that can be turned into a table of values or can be NULL, such as @Values VARCHAR(10) = NULL ...
0
votes
1answer
2k views

How to show NULL results from query?

i'm trying to create a procedure with filters for search. If the parameter is "NULL" the value of parameter will be column value; Here my problem: When my parameter and column value is NULL. I have ...
0
votes
1answer
260 views

Geography union via cursor returning null

I need to combine multiple geography records into a single entity to store in a spatial data table, but I've learned that the only available function in MSSQL2008R2 that accomplishes this task is ...
-1
votes
1answer
1k views

Totals Column - Blank if Zero or NULL

A report currently computes a "totals" column like so: ,CASE WHEN ISNULL(CLM_BREAKFAST_TYPEA.MealsA, 0) + ISNULL(CLM_BREAKFAST_TYPEB.MealsB, 0) = 0 THEN '' ...
3
votes
3answers
3k views

Query to find GUID's “not in” null containing subquery returns no results

When I have a query that checks if a column of type uniqueidentifer does not exist in a table that has a null value then I get no results back. If the subquery does not return a null it works fine and ...
3
votes
1answer
96 views

How to get 0 as array_length() result when there are no elements

I have a query like this: select id, array_length(users_who_like_ids,1) as ct from queryables order by 2 desc; But empty arrays (with no elements) sort on top. I'd rather have array_length() return ...
1
vote
1answer
189 views

INSERT don't work with NOT NULL but UPDATE does, why?

I have this table definition: CREATE TABLE `media` ( `id` int(11) NOT NULL AUTO_INCREMENT, `brands_id` int(11) DEFAULT NULL, `media_type` varchar(45) COLLATE utf8_unicode_ci DEFAULT NULL, `...
4
votes
2answers
455 views

Adding hstore entries to an uninitialized (NULL) column

I got bitten by this "feature" recently. If your hstore column is uninitialized and you start adding entries to it, they are all silently swallowed without error. Is this expected? create table ...
7
votes
2answers
1k views

Why is a NOT NULL computed column considered nullable in a view?

I have a table: CREATE TABLE [dbo].[Realty]( [Id] [int] IDENTITY(1,1) NOT NULL, [RankingBonus] [int] NOT NULL, [Ranking] AS ([Id]+[RankingBonus]) PERSISTED NOT NULL .... ) And a ...
9
votes
2answers
4k views

How can I help SQL Server recognize my indexed view column is NOT NULL-able?

I have the following indexed view defined in SQL Server 2008 (you can download a working schema from gist for testing purposes): CREATE VIEW dbo.balances WITH SCHEMABINDING AS SELECT user_id ...
0
votes
1answer
1k 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?
5
votes
4answers
3k views

How to exclude NULL values inside CONCAT MySQL?

If I have this - tadd is the Address table: CONCAT(tadd.street_number, ' ', tadd.street_name,', ', tadd.apt_number,', ', tadd.city,', ', tadd....
2
votes
1answer
227 views

Unique Index/Constraint with multiple columns, one column is nullable

My questions is whether it's possible to have unique index comprised of multiple columns where one of the columns may contain NULL. Example: A table named 'regulated_person' has a number of columns ...
3
votes
1answer
135 views

Display non-null and null count using case statement

In total there are 10 values in my table, 5 of which are null. I need to display the count using case statement in Oracle, like output below: Sample Data: +------+ | Eid | +------+ | 1 | | 2 |...
2
votes
1answer
72 views

Why does coalescing make this query quicker?

I have the following query SELECT SQL_NO_CACHE `table1`.* FROM `table1` LEFT JOIN `table2` ON table2.id = table1.table2_id WHERE (`table2`.`date_assigned` >= '2015-06-21') AND ( ...
1
vote
1answer
93 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?