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### What changes were proposed in this pull request? Document identifier in SQL Reference ### Why are the changes needed? make SQL Reference complete ### Does this PR introduce any user-facing change? Yes <img width="1049" alt="Screen Shot 2020-04-23 at 11 14 10 PM" src="https://user-images.githubusercontent.com/13592258/80180695-2f2a4f00-85b8-11ea-819b-f96872956d05.png"> <img width="1050" alt="Screen Shot 2020-04-23 at 11 32 32 PM" src="https://user-images.githubusercontent.com/13592258/80182062-e6c06080-85ba-11ea-9502-1c38358c97c9.png"> ### How was this patch tested? Manually build and check Closes #28277 from huaxingao/identifier. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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| layout | title | displayTitle | license |
|---|---|---|---|
| global | Identifiers | Identifiers | Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. |
Description
An identifier is a string used to identify a database object such as a table, view, schema, column, etc. Spark SQL has regular identifiers and delimited identifiers, which are enclosed within backticks. Both regular identifiers and delimited identifiers are case-insensitive.
Syntax
Regular Identifier
{% highlight sql %}
{ letter | digit | '_' } [ , ... ]
{% endhighlight %}
Note: If spark.sql.ansi.enabled is set to true, ANSI SQL reserved keywords cannot be used as identifiers. For more details, please refer to ANSI Compliance.
Delimited Identifier
{% highlight sql %}
c [ ... ]
{% endhighlight %}
Parameters
letter- Any letter from A-Z or a-z.
digit- Any numeral from 0 to 9.
c-
Any character from the character set. Use
`to escape special characters (e.g.,`).
Examples
{% highlight sql %} -- This CREATE TABLE fails with ParseException because of the illegal identifier name a.b CREATE TABLE test (a.b int); org.apache.spark.sql.catalyst.parser.ParseException: no viable alternative at input 'CREATE TABLE test (a.'(line 1, pos 20)
-- This CREATE TABLE works
CREATE TABLE test (a.b int);
-- This CREATE TABLE fails with ParseException because special character is not escaped CREATE TABLE test1 (ab int);
org.apache.spark.sql.catalyst.parser.ParseException:
no viable alternative at input 'CREATE TABLE test (ab`'(line 1, pos 23)
-- This CREATE TABLE works
CREATE TABLE test (a``b int);
{% endhighlight %}