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

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63 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 ( ...
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0answers
23 views

How to best distinguish between “types” of missing data?

I am working on large tables (> 100 fields each) currently organized in flat-files in csv-format. An Oracle DB is to be created to store all the data and allow for several more or less intricate ...
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0answers
96 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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0answers
116 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
94 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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30 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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402 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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57 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 ...