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

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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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78 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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40 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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76 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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61 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 ...
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41 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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120 views

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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29 views

Import CSV script executes and returns NULL on localhost

I have been running this import script on localhost to import CSV fields to my database. The script executes and returns the rows as NULL and no data is inserted. It would be great to get another set ...
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48 views

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 ...