dtenedor commented on code in PR #36950:
URL: https://github.com/apache/spark/pull/36950#discussion_r908766310
##########
docs/sql-ref-number-pattern.md:
##########
@@ -19,4 +19,165 @@ license: |
limitations under the License.
---
-TODO: Add the content of Number Patterns for Formatting and Parsing
+### Description
+
+Functions such as `to_number` and `to_char` support converting between values
of string and
+Decimal type. Such functions accept format strings indicating how to map
between these types.
+
+### Syntax
+
+Number format strings support the following syntax:
+
+```
+ { ' [ S ] [ $ ]
+ [ 0 | 9 | G | , ] [...]
+ [ . | D ]
+ [ 0 | 9 ] [...]
+ [ $ ] [ PR | MI | S ] ' }
+```
+
+### Elements
+
+Each number format string can contain the following elements (case
insensitive):
+
+- **`0`** or **`9`**
+
+ Specifies an expected digit between `0` and `9`.
+
+ A sequence of 0 or 9 in the format string matches a sequence of digits with
the same or smaller
+ size. If the 0/9 sequence starts with 0 and is before the decimal point, it
requires matching the
+ number of digits: when parsing, it matches only a digit sequence of the same
size; when
+ formatting, the result string adds left-padding with zeros to the digit
sequence to reach the
+ same size. Otherwise, the 0/9 sequence matches any digit sequence with the
same or smaller size
+ when parsing, and pads the digit sequence with spaces in the result string
when formatting. Note
+ that the digit sequence will become a '#' sequence if the size is larger
than the 0/9 sequence.
+
+- **`.`** or **`D`**
+
+ Specifies the position of the decimal point.
+
+ The input value does not need to include a decimal point.
+
+- **`,`** or **`G`**
+
+ Specifies the position of the `,` grouping (thousands) separator.
+
+ There must be a `0` or `9` to the left and right of each grouping separator.
+
+- **`$`**
+
+ Specifies the location of the `$` currency sign. This character may only be
specified once.
+
+- **`S`**
+
+ Specifies the position of an optional '+' or '-' sign. This character may
only be specified once.
+
+- **`MI`**
+
+ Specifies an optional `-` sign at the end, but no `+`.
Review Comment:
Good catch -- we ended up allowing `MI` at the beginning as well during
conversations while building the feature. I updated these docs accordingly.
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