DaveBirdsall commented on a change in pull request #1767: [TRAFODION-3254] Add
*SPLIT_PART Function* in Trafodion SQL Reference Manual
URL: https://github.com/apache/trafodion/pull/1767#discussion_r248090026
##########
File path:
docs/sql_reference/src/asciidoc/_chapters/sql_functions_and_expressions.adoc
##########
@@ -8829,6 +8829,222 @@ with the character set specified by _char-set-name_.
SPACE(3)
```
+<<<
+[[split_part_function]]
+== SPLIT_PART Function
+
+The SPLIT_PART function returns the n^th^ substring that is split on the
defined `_delimiter_` and `_filed-position_`.
+
+SPLIT_PART is a Trafodion SQL extension.
+
+`SPLIT_PART (_source-string, delimiter, filed-position_)`
+
+[[syntax_description_of_split_part]]
+=== Syntax Description of SPLIT_PART
+
+* `_source-string_`
++
+is a string to be split.
++
+NOTE: The `_source-string_` must be character and cannot be NULL.
+
+* `_delimiter_`
++
+is a delimiter to split a `_source-string_`.
++
+The delimiter can contain multiple characters, not just a single character.
Multiple characters are considered as a whole, not individually. For example,
if the delimiter is "coder", then the source-string is split around "coder"
rather than "c", "o", "d", "e" and "r".
++
+NOTE: The `_delimiter_` cannot be NULL.
++
+NOTE: The function counts from the first `_delimiter_` if the `_delimiter_`
appears more than once in the souce-string.
++
+Example
++
+```
+SQL>SELECT SPLIT_PART ('technical writer','t',2) FROM DUAL;
+
+(EXPR)
+------------------------
+echnical wri
+
+--- 1 row(s) selected.
+```
++
+NOTE: The function returns an empty string if the `_delimiter_` does not exist
in the souce-string.
++
+Example
++
+```
+SQL>SELECT SPLIT_PART ('technical_writer','@_@',1) FROM DUAL;
+
+(EXPR)
+----------------------
+
+
+--- 1 row(s) selected.
+```
++
+NOTE: Empty space before of after the `_delimiter_` is served as a valid part
if the `_source-string_` starts or ends with the `_delimiter_`.
++
+Example
++
+```
+SQL>SELECT SPLIT_PART ('|t|e|c|h|n|i|c|a|l', '|', 1), SPLIT_PART
('|w|r|i|t|e|r|', '|', 8) FROM DUAL;
+
+(EXPR) (EXPR)
+------------------ -------------
+
+
+--- 1 row(s) selected.
+```
+
+* `_filed-position_`
++
+is the n^th^ part of the `_souce-string_` to return.
++
+NOTE: The `_filed-position_` must be an integer greater than 0.
++
+NOTE: The `_filed-position_` cannot be NULL.
++
+NOTE: The function returns an empty string if the `_filed-position_` exceeds
the number of `_souce-string_` parts after splitting.
++
+Example
++
+```
+SQL>SELECT SPLIT_PART ('technical writer',' ',3) FROM DUAL;
+
+(EXPR)
+----------------
+
+
+--- 1 row(s) selected.
+```
+
+[[considertaion_for_split_part]]
+=== Considertaion for SPLIT_PART
+
+This function returns an empty string if any parameter is NULL.
Review comment:
I found this was not true. If NULL is supplied for any parameter, we get
error 4097, as you described above. If I have a nullable column, and one of the
rows has a null value in that column, I found that SPLIT_PART returned a null
value instead. (This surprised me, actually; I would expect that
split_part(null,'x',3) would have the same behavior as split_part(col1,'x',3)
if col1 happens to be null. I think that is a bug.)
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