sql-ref-identifier-clause.md

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global	Identifier clause	IDENTIFIER clause	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

Converts a constant STRING expression into a SQL object name. The purpose of this clause is to allow for templating of identifiers in SQL statements without opening up the risk of SQL injection attacks. Typically, this clause is used with a parameter marker or a variable as argument.

Syntax

IDENTIFIER ( strExpr )

Parameters

• strExpr: A constant STRING expression. Typically, the expression includes a parameter marker.

Returns

A (qualified) identifier which can be used as a:

• qualified table name
• namespace name
• function name
• qualified column or attribute reference

Examples

Scala examples

These examples use named parameter markers to templatize queries.

// Creation of a table using parameter marker.
spark.sql("CREATE TABLE IDENTIFIER(:mytab)(c1 INT)", args = Map("mytab" -> "tab1")).show()

spark.sql("DESCRIBE IDENTIFIER(:mytab)", args = Map("mytab" -> "tab1")).show()
+--------+---------+-------+
|col_name|data_type|comment|
+--------+---------+-------+
|      c1|      int|   NULL|
+--------+---------+-------+

// Altering a table with a fixed schema and a parameterized table name. 
spark.sql("ALTER TABLE IDENTIFIER('default.' || :mytab) ADD COLUMN c2 INT", args = Map("mytab" -> "tab1")).show()

spark.sql("DESCRIBE IDENTIFIER(:mytab)", args = Map("mytab" -> "default.tab1")).show()
+--------+---------+-------+
|col_name|data_type|comment|
+--------+---------+-------+
|      c1|      int|   NULL|
|      c2|      int|   NULL|
+--------+---------+-------+

// A parameterized reference to a table in a query. This table name is qualified and uses back-ticks.
spark.sql("SELECT * FROM IDENTIFIER(:mytab)", args = Map("mytab" -> "`default`.`tab1`")).show()
+---+---+
| c1| c2|
+---+---+
+---+---+


// You cannot qualify the IDENTIFIER clause or use it as a qualifier itself.
spark.sql("SELECT * FROM myschema.IDENTIFIER(:mytab)", args = Map("mytab" -> "`tab1`")).show()
[INVALID_SQL_SYNTAX.INVALID_TABLE_VALUED_FUNC_NAME] `myschema`.`IDENTIFIER`.

spark.sql("SELECT * FROM IDENTIFIER(:myschema).mytab", args = Map("mychema" -> "`default`")).show()
[PARSE_SYNTAX_ERROR]

// Dropping a table with separate schema and table parameters.
spark.sql("DROP TABLE IDENTIFIER(:myschema || '.' || :mytab)", args = Map("myschema" -> "default", "mytab" -> "tab1")).show()

// A parameterized column reference
spark.sql("SELECT IDENTIFIER(:col) FROM VALUES(1) AS T(c1)", args = Map("col" -> "t.c1")).show()
+---+
| c1|
+---+
|  1|
+---+

// Passing in a function name as a parameter
spark.sql("SELECT IDENTIFIER(:func)(-1)", args = Map("func" -> "abs")).show();
+-------+
|abs(-1)|
+-------+
|      1|
+-------+

SQL examples

These examples use SQL variables to templatize queries.

DECLARE mytab = 'tab1';

-- Creation of a table using variable.
CREATE TABLE IDENTIFIER(mytab)(c1 INT);

DESCRIBE IDENTIFIER(mytab);
+--------+---------+-------+
|col_name|data_type|comment|
+--------+---------+-------+
|      c1|      int|   NULL|
+--------+---------+-------+

-- Altering a table with a fixed schema and a parameterized table name. 
ALTER TABLE IDENTIFIER('default.' || mytab) ADD COLUMN c2 INT;

SET VAR mytab = '`default`.`tab1`';
DESCRIBE IDENTIFIER(mytab);
+--------+---------+-------+
|col_name|data_type|comment|
+--------+---------+-------+
|      c1|      int|   NULL|
|      c2|      int|   NULL|
+--------+---------+-------+

-- A parameterized reference to a table in a query. This table name is qualified and uses back-ticks.
SELECT * FROM IDENTIFIER(mytab);
+---+---+
| c1| c2|
+---+---+
+---+---+


-- Dropping a table with separate schema and table parameters.
DECLARE myschema = 'default';
SET VAR mytab = 'tab1';
DROP TABLE IDENTIFIER(myschema || '.' || mytab);

-- A parameterized column reference
DECLARE col = 't.c1';
SELECT IDENTIFIER(col) FROM VALUES(1) AS T(c1);
+---+
| c1|
+---+
|  1|
+---+

-- Passing in a function name as a parameter
DECLARE func = 'abs';
SELECT IDENTIFIER(func)(-1);
+-------+
|abs(-1)|
+-------+
|      1|
+-------+