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DOC: Add examples to the SQL docs (#31633)
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Significantly improve the example snippets in the documentation.
The examples are part of the test suite and checked nightly.
To help readability, the existing dataset was extended (test_emp renamed
to emp plus library).
Improve output of JDBC tests to be consistent with the CLI
Add lenient flag to JDBC asserts to allow type widening (a long is
equivalent to a integer as long as the value is the same).

(cherry picked from commit de9e56a)
(cherry picked from commit 77f5e17)
(cherry picked from commit 093ea03)
(cherry picked from commit b342552)
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costin committed Jul 3, 2018
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5 changes: 5 additions & 0 deletions docs/reference/sql/language/syntax/describe-table.asciidoc
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Expand Up @@ -20,3 +20,8 @@ DESC table
.Description

`DESC` and `DESCRIBE` are aliases to <<sql-syntax-show-columns>>.

["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[describeTable]
----
255 changes: 164 additions & 91 deletions docs/reference/sql/language/syntax/select.asciidoc
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Expand Up @@ -36,23 +36,26 @@ The general execution of `SELECT` is as follows:

As with a table, every output column of a `SELECT` has a name which can be either specified per column through the `AS` keyword :

[source,sql]
["source","sql",subs="attributes,callouts,macros"]
----
SELECT column AS c
include-tagged::{sql-specs}/docs.csv-spec[selectColumnAlias]
----

Note: `AS` is an optional keyword however it helps with the readability and in some case ambiguity of the query
which is why it is recommended to specify it.

assigned by {es-sql} if no name is given:

[source,sql]
["source","sql",subs="attributes,callouts,macros"]
----
SELECT 1 + 1
include-tagged::{sql-specs}/docs.csv-spec[selectInline]
----

or if it's a simple column reference, use its name as the column name:

[source,sql]
["source","sql",subs="attributes,callouts,macros"]
----
SELECT col FROM table
include-tagged::{sql-specs}/docs.csv-spec[selectColumn]
----

[[sql-syntax-select-wildcard]]
Expand All @@ -61,11 +64,11 @@ SELECT col FROM table
To select all the columns in the source, one can use `*`:

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

which essentially returns all columsn found.
which essentially returns all(top-level fields, sub-fields, such as multi-fields are ignored] columns found.

[[sql-syntax-from]]
[float]
Expand All @@ -83,17 +86,30 @@ where:
`table_name`::

Represents the name (optionally qualified) of an existing table, either a concrete or base one (actual index) or alias.


If the table name contains special SQL characters (such as `.`,`-`,etc...) use double quotes to escape them:
[source, sql]

["source","sql",subs="attributes,callouts,macros"]
----
SELECT ... FROM "some-table"
include-tagged::{sql-specs}/docs.csv-spec[fromTableQuoted]
----

The name can be a <<multi-index, pattern>> pointing to multiple indices (likely requiring quoting as mentioned above) with the restriction that *all* resolved concrete tables have **exact mapping**.

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

`alias`::
A substitute name for the `FROM` item containing the alias. An alias is used for brevity or to eliminate ambiguity. When an alias is provided, it completely hides the actual name of the table and must be used in its place.

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

[[sql-syntax-where]]
[float]
==== WHERE Clause
Expand All @@ -111,6 +127,11 @@ where:

Represents an expression that evaluates to a `boolean`. Only the rows that match the condition (to `true`) are returned.

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

[[sql-syntax-group-by]]
[float]
==== GROUP BY
Expand All @@ -126,9 +147,79 @@ where:

`grouping_element`::

Represents an expression on which rows are being grouped _on_. It can be a column name, name or ordinal number of a column or an arbitrary expression of column values.
Represents an expression on which rows are being grouped _on_. It can be a column name, alias or ordinal number of a column or an arbitrary expression of column values.

A common, group by column name:

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

Grouping by output ordinal:

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

Grouping by alias:

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

And grouping by column expression (typically used along-side an alias):

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

When a `GROUP BY` clause is used in a `SELECT`, _all_ output expressions must be either aggregate functions or expressions used for grouping or derivatives of (otherwise there would be more than one possible value to return for each ungrouped column).

To wit:

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

Expressions over aggregates used in output:

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

Multiple aggregates used:

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

[[sql-syntax-group-by-implicit]]
[float]
===== Implicit Grouping

When an aggregation is used without an associated `GROUP BY`, an __implicit grouping__ is applied, meaning all selected rows are considered to form a single default, or implicit group.
As such, the query emits only a single row (as there is only a single group).

A common example is counting the number of records:

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

Of course, multiple aggregations can be applied:

When a `GROUP BY` clause is used in a `SELECT`, _all_ output expressions must be either aggregate functions or expressions used for grouping or derivates of (otherwise there would be more than one possible value to return for each ungrouped column).
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[groupByImplicitMultipleAggs]
----

[[sql-syntax-having]]
[float]
Expand All @@ -147,13 +238,44 @@ where:

Represents an expression that evaluates to a `boolean`. Only groups that match the condition (to `true`) are returned.

Both `WHERE` and `HAVING` are used for filtering however there are several differences between them:
Both `WHERE` and `HAVING` are used for filtering however there are several significant differences between them:

. `WHERE` works on individual *rows*, `HAVING` works on the *groups* created by ``GROUP BY``
. `WHERE` is evaluated *before* grouping, `HAVING` is evaluated *after* grouping

Note that it is possible to have a `HAVING` clause without a ``GROUP BY``. In this case, an __implicit grouping__ is applied, meaning all selected rows are considered to form a single group and `HAVING` can be applied on any of the aggregate functions specified on this group. `
As such a query emits only a single row (as there is only a single group), `HAVING` condition returns either one row (the group) or zero if the condition fails.
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[groupByHaving]
----

Further more, one can use multiple aggregate expressions inside `HAVING` even ones that are not used in the output (`SELECT`):

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

[[sql-syntax-having-group-by-implicit]]
[float]
===== Implicit Grouping

As indicated above, it is possible to have a `HAVING` clause without a ``GROUP BY``. In this case, the so-called <<sql-syntax-group-by-implicit, __implicit grouping__>> is applied, meaning all selected rows are considered to form a single group and `HAVING` can be applied on any of the aggregate functions specified on this group. `
As such, the query emits only a single row (as there is only a single group) and `HAVING` condition returns either one row (the group) or zero if the condition fails.

In this example, `HAVING` matches:

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

//However `HAVING` can also not match, in which case an empty result is returned:
//
//["source","sql",subs="attributes,callouts,macros"]
//----
//include-tagged::{sql-specs}/docs.csv-spec[groupByHavingImplicitNoMatch]
//----
[[sql-syntax-order-by]]
[float]
Expand All @@ -178,30 +300,10 @@ IMPORTANT: When used along-side, `GROUP BY` expression can point _only_ to the c
For example, the following query sorts by an arbitrary input field (`page_count`):
[source,js]
--------------------------------------------------
POST /_xpack/sql?format=txt
{
"query": "SELECT * FROM library ORDER BY page_count DESC LIMIT 5"
}
--------------------------------------------------
// CONSOLE
// TEST[setup:library]

which results in something like:

[source,text]
--------------------------------------------------
author | name | page_count | release_date
-----------------+--------------------+---------------+------------------------
Peter F. Hamilton|Pandora's Star |768 |2004-03-02T00:00:00.000Z
Vernor Vinge |A Fire Upon the Deep|613 |1992-06-01T00:00:00.000Z
Frank Herbert |Dune |604 |1965-06-01T00:00:00.000Z
Alastair Reynolds|Revelation Space |585 |2000-03-15T00:00:00.000Z
James S.A. Corey |Leviathan Wakes |561 |2011-06-02T00:00:00.000Z
--------------------------------------------------
// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/]
// TESTRESPONSE[_cat]
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[orderByBasic]
----
[[sql-syntax-order-by-score]]
==== Order By Score
Expand All @@ -215,58 +317,22 @@ combined using the same rules as {es}'s
To sort based on the `score`, use the special function `SCORE()`:
[source,js]
--------------------------------------------------
POST /_xpack/sql?format=txt
{
"query": "SELECT SCORE(), * FROM library WHERE match(name, 'dune') ORDER BY SCORE() DESC"
}
--------------------------------------------------
// CONSOLE
// TEST[setup:library]

Which results in something like:

[source,text]
--------------------------------------------------
SCORE() | author | name | page_count | release_date
---------------+---------------+-------------------+---------------+------------------------
2.288635 |Frank Herbert |Dune |604 |1965-06-01T00:00:00.000Z
1.8893257 |Frank Herbert |Dune Messiah |331 |1969-10-15T00:00:00.000Z
1.6086555 |Frank Herbert |Children of Dune |408 |1976-04-21T00:00:00.000Z
1.4005898 |Frank Herbert |God Emperor of Dune|454 |1981-05-28T00:00:00.000Z
--------------------------------------------------
// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/ s/\(/\\\(/ s/\)/\\\)/]
// TESTRESPONSE[_cat]

Note that you can return `SCORE()` by adding it to the where clause. This
is possible even if you are not sorting by `SCORE()`:

[source,js]
--------------------------------------------------
POST /_xpack/sql?format=txt
{
"query": "SELECT SCORE(), * FROM library WHERE match(name, 'dune') ORDER BY page_count DESC"
}
--------------------------------------------------
// CONSOLE
// TEST[setup:library]

[source,text]
--------------------------------------------------
SCORE() | author | name | page_count | release_date
---------------+---------------+-------------------+---------------+------------------------
2.288635 |Frank Herbert |Dune |604 |1965-06-01T00:00:00.000Z
1.4005898 |Frank Herbert |God Emperor of Dune|454 |1981-05-28T00:00:00.000Z
1.6086555 |Frank Herbert |Children of Dune |408 |1976-04-21T00:00:00.000Z
1.8893257 |Frank Herbert |Dune Messiah |331 |1969-10-15T00:00:00.000Z
--------------------------------------------------
// TESTRESPONSE[s/\|/\\|/ s/\+/\\+/ s/\(/\\\(/ s/\)/\\\)/]
// TESTRESPONSE[_cat]
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[orderByScore]
----
Note that you can return `SCORE()` by using a full-text search predicate in the `WHERE` clause.
This is possible even if `SCORE()` is not used for sorting:
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[orderByScoreWithMatch]
----
NOTE:
Trying to return `score` from a non full-text queries will return the same value for all results, as
all are equilley relevant.
Trying to return `score` from a non full-text query will return the same value for all results, as
all are equally relevant.
[[sql-syntax-limit]]
[float]
Expand All @@ -284,3 +350,10 @@ where
count:: is a positive integer or zero indicating the maximum *possible* number of results being returned (as there might be less matches than the limit). If `0` is specified, no results are returned.
ALL:: indicates there is no limit and thus all results are being returned.
To return
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[limitBasic]
----
5 changes: 5 additions & 0 deletions docs/reference/sql/language/syntax/show-columns.asciidoc
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Expand Up @@ -12,3 +12,8 @@ SHOW COLUMNS [ FROM | IN ] ? table
.Description

List the columns in table and their data type (and other attributes).

["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[showColumns]
----
31 changes: 31 additions & 0 deletions docs/reference/sql/language/syntax/show-functions.asciidoc
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Expand Up @@ -14,3 +14,34 @@ SHOW FUNCTIONS [ LIKE? pattern<1>? ]?
.Description

List all the SQL functions and their type. The `LIKE` clause can be used to restrict the list of names to the given pattern.

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

The list of functions returned can be customized based on the pattern.

It can be an exact match:
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[showFunctionsLikeExact]
----

A wildcard for exactly one character:
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[showFunctionsLikeChar]
----

A wildcard matching zero or more characters:
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[showFunctionsLikeWildcard]
----

Or of course, a variation of the above:
["source","sql",subs="attributes,callouts,macros"]
----
include-tagged::{sql-specs}/docs.csv-spec[showFunctionsWithPattern]
----
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