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

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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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367 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?
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If I assign a NVL constraint to a nullable column will it display an error or it will retrieve the records?

I have a database in which some tables have to be joined to fetch the data. The problem is that in one table the column is nullable (nullable is set to yes or no constraint given for that column) and ...
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Oracle 12c, exclude rows wher two columns are both null

Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit I am trying to select rows with a non-null value in one of two columns. Data is being selected from a view (MY_VIEW) with both ...
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MySQL - query join returning zero recs from table with data

I've provided a file that has the table structure and some sample data that I'm working with. I don't understand why I'm getting nulls from a joined table, where there is data. Here's my query ...
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190 views

Accept null value on parent column in multipart relationship

EDIT: I've come up with one poor solution (below) that requires some denormalization, but does avoid the risks of UDFs in CHECK constraints. I would appreciate your help if you have a better answer. ...
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490 views

H2 SELECT NULLABLE or other equivalent to check a column has NOT NULL constraint or not

I would like to check if a column has a NOT NULL constraint in order to start an automated upgrade of the table definition. However in H2 the SQL SELECT NULLABLE FROM TABLE_NAME doesn't return me the ...
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Inserting null value without quotes postgresql

I'm creating a php application which relies on postgresql. Now i have this query: $query= 'INSERT INTO "users" ("name", "username", "email", "phone") VALUES (\''. $name .'\', \''. $username .'\', ...