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SQL: [docs] Add documentation for COALESCE #35740

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Nov 21, 2018
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SQL: [docs] Add documentation for COALESCE #35740

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SQL: [docs] Add documentation for COALESCE
matriv Nov 20, 2018
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matriv Nov 20, 2018
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46 changes: 46 additions & 0 deletions docs/reference/sql/functions/conditional.asciidoc
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Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
[role="xpack"]
[testenv="basic"]
[[sql-functions-conditional]]
=== Conditional Functions

Functions that return one of their arguments by evaluating in an if-else manner.

[[sql-functions-conditional-coalesce]]
==== `COALESCE`

.Synopsis
[source, sql]
----
COALESCE ( expression<1>, expression<2>, ... )
----

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Enumerating the parameters should happen in a section called Input. Also, there has to be an Output section. Something like:

==== `COALESCE`

.Synopsis:
[source, sql]
--------------------------------------------------
COALESCE ( expression<1>, expression<2>, ... )
--------------------------------------------------

*Input*:

<1> 1st expression
<2> 2nd expression
....

*Output*: one expression or `null`

.Description:

Returns the first of its arguments that is not null.
If all arguments are null, then it returns `null`.

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Also, I would add in the description (to enforce the ... in the parameters list), that the function can take an arbitrary number of arguments.

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The statement about arbitrary number of arguments is there. Please, ignore my comment.

*Input*:

<1> 1st expression

<2> 2nd expression

...

**N**th expression

COALESCE can take an arbitrary number of arguments.

*Output*: one of the expressions or `null`

.Description

Returns the first of its arguments that is not null.
If all arguments are null, then it returns `null`.



["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[coalesceReturnNonNull]
----

["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[coalesceReturnNull]
----
2 changes: 2 additions & 0 deletions docs/reference/sql/functions/index.asciidoc
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Expand Up @@ -12,6 +12,7 @@
* <<sql-functions-math, Mathematical>>
* <<sql-functions-string, String>>
* <<sql-functions-type-conversion,Type Conversion>>
* <<sql-functions-conditional, Conditional>>

include::operators.asciidoc[]
include::aggs.asciidoc[]
Expand All @@ -20,3 +21,4 @@ include::search.asciidoc[]
include::math.asciidoc[]
include::string.asciidoc[]
include::type-conversion.asciidoc[]
include::conditional.asciidoc[]
21 changes: 21 additions & 0 deletions x-pack/plugin/sql/qa/src/main/resources/docs.csv-spec
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Expand Up @@ -1510,3 +1510,24 @@ SELECT TRUNCATE(-345.153, 1) AS trimmed;
// end::mathTruncateWithPositiveParameter
;


coalesceReturnNonNull
// tag::coalesceReturnNonNull
SELECT COALESCE(null, 'elastic', 'search') AS "coalesce";

coalesce
---------------
elastic
// end::coalesceReturnNonNull
;


coalesceReturnNull
// tag::coalesceReturnNull
SELECT COALESCE(null, null, null, null) AS "coalesce";

coalesce
---------------
null
// end::coalesceReturnNull
;