spark-instrumented-optimizer/docs/sql-ref-identifier.md

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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

{ letter | digit | '_' } [ , ... ]

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

`c [ ... ]`

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 </code> to escape special characters (e.g., <code>).

Examples

-- 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 (`a`b` int);
org.apache.spark.sql.catalyst.parser.ParseException:
no viable alternative at input 'CREATE TABLE test (`a`b`'(line 1, pos 23)

-- This CREATE TABLE works
CREATE TABLE test (`a``b` int);