docs: add tutorial with examples of sql null handling #16185
Conversation
| Before starting this tutorial, download and run Apache Druid on your local machine as described in | ||
| the [Local quickstart](index.md). | ||
|
|
||
| The tutorial assumes you are familiar with using the [Query view](./tutorial-sql-query-view.md) to ingest and query data. |
There was a problem hiding this comment.
i wonder if we need to call out that this tutorial expects druid.generic.useDefaultValueForNull and druid.generic.useThreeValueLogicForNativeFilters to be set to their default values of false and true respectively or if that would be confusing
There was a problem hiding this comment.
added a comment without detail since we don't want folks changing it if they're just getting started.
docs/querying/sql-data-types.md
Outdated
| runtime property controls Druid's NULL handling mode. For the most SQL compliant behavior, maintain the default value of `false`. | ||
|
|
||
| There is some performance impact for null handling. see [segment internals](../design/segments.md#handling-null-values) for more information. | ||
| For examples of null handling, see the [null handling tutorial](../tutorials/tutorial-ansi-sql-null.md). |
There was a problem hiding this comment.
link seems wrong, filename is tutorial-sql-null.md
| For example, the following expressions are equivalent: | ||
| - col IS NULL | ||
| - col = '' | ||
| Both evaluate to true if col contains an empty string. |
docs/tutorials/tutorial-sql-null.md
Outdated
|
|
||
| ## Load data with null values | ||
|
|
||
| The tutorial loads some data with null values for string and numeric columns as follows: |
There was a problem hiding this comment.
The tutorial doesn't load data for them. Rather, they need to load dat for the tutorial, right?
| SELECT * FROM "null_example" | ||
| ``` | ||
|
|
||
| |`__time`|`title`|`string_value`|`numeric_value`| |
There was a problem hiding this comment.
The table has empty columns:
docs/tutorials/tutorial-sql-null.md
Outdated
|
|
||
| Druid returns 2 for "another_value" and the empty string "". The null value is not counted. | ||
|
|
||
| Note that the null value is included in COUNT(*) but not as a count of the values in the column as follows: |
There was a problem hiding this comment.
code font for COUNT(*) since it's a specific instance of COUNT and not COUNT as a function in general
docs/tutorials/tutorial-sql-null.md
Outdated
| GROUP BY 1 | ||
| ``` | ||
|
|
||
| Druid returns the following data: |
There was a problem hiding this comment.
Your results above odn't have an intro sentence like this, and a subsequent intro sentence is slightly different, but that's not a huge deal
|
|
||
| The resulting data set only includes two rows. Druid has filtered out example 1 (`some_value`) and example 4 (`null`): | ||
|
|
||
| |`__time`|`title`|`string_value`|`numeric_value`| |
Co-authored-by: 317brian <53799971+317brian@users.noreply.github.com>
Co-authored-by: 317brian <53799971+317brian@users.noreply.github.com>
Co-authored-by: 317brian <53799971+317brian@users.noreply.github.com>
Co-authored-by: 317brian <53799971+317brian@users.noreply.github.com>
317brian
changed the title
Description
This PR has: