IDENTIFIER 子句

適用於： Databricks SQL Databricks Runtime 13.3 LTS 和更新版本

IDENTIFIER 子句會將常數位符串解譯為：

• 數據表或檢視名稱
• 函數名稱
• 數據行名稱
• 功能變數名稱
• 架構名稱

子句會啟用 SQL 語句的 SQL 插入式安全參數化。

下列語句支援IDENTIFIER子句：

• CREATE、ALTER、DROP、UNDROP 的數據表、檢視或函數名稱
• MERGE、UPDATE、DELETE、INSERT、COPY INTO 的數據表名稱
• SHOW 或 DESCRIBE 的目標
• 使用架構
• 函式調用
• 查詢中所參考的數據行或檢視。 這包括內嵌在 DDL 或 DML 語句中的查詢。

使用identifier子句時，它可能不會內嵌在標識碼內。

語法

IDENTIFIER ( strExpr )

參數

• strExpr：常數 STRING 運算式通常包含一或多個 參數標記。

範例

Scala

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

// 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"))

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

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

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

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

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

// Passing in an aggregate function name as a parameter
spark.sql("SELECT IDENTIFIER(agg)(c1) FROM VALUES(1), (2) AS T(c1)", args = Map("agg" -> "max"))

SQL

-- Creation of a table using variable.
> DECLARE mytab = 'tab1';
> CREATE TABLE IDENTIFIER(mytab)(c1 INT);

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

-- Inserting using a parameterized table name. The table name is qualified and uses back-ticks.
> SET VAR mytab = '`default`.`tab1`';
> INSERT INTO IDENTIFIER(mytab) VALUES(1, 2);

-- A parameterized reference to a table in a query.
> SELECT * FROM IDENTIFIER(mytab);
  1   2

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

 -- You cannot qualify the IDENTIFIER claue or use it as a qualifier itself.
> SELECT * FROM myschema.IDENTIFIER('tab');
Error: PARSE_SYNTAX_ERROR

> SELECT * FROM IDENTIFIER('default').mytab;
Error: PARSE_SYNTAX_ERROR

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

-- Passing in an aggregate function name as a parameter
> DECLARE agg = 'max';
> SELECT IDENTIFIER(agg)(c1) FROM VALUES(1), (2) AS T(c1);
  2

相關

• 識別碼
• 參數標記
• 名稱