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SET VARIABLE

  • Artikkeli

Applies to: check marked yes Databricks SQL check marked yes Databricks Runtime 14.1 and above

Modifies the value of one or more temporary variables.

To set a configuration parameter use SET.

Syntax

SET { VAR | VARIABLE } { variable_name = { expression | DEFAULT } } [, ...]

SET { VAR | VARIABLE } ( variable_name [, ...] ) = ( query ) }

Parameters

  • variable_name

    Specifies the name of a temporary variable.

    If the variable cannot be found Azure Databricks raises an UNRESOLVED_VARIABLE error.

    If you specify duplicate variables Azure Databricks raises an DUPLICATE_ASSIGNMENTS error.

  • expression

    Any well-formed expression computing the new variable value.

  • DEFAULT

    Used the default expression of the variable or NULL if none was specified to compute the new variable value.

  • query

    Any well-formed query with the following restrictions:

    If the query returns no rows Azure Databricks sets all specified variables to NULL.

    You can use the DEFAULT keyword instead of a select-list expression to set a variable to its default.

Examples

> DECLARE VARIABLE myvar1 INT DEFAULT 7;
> DECLARE VARIABLE myvar2 STRING DEFAULT ‘hello’;

-- Set a SQL variable to a value
> SET VAR myvar1 = 5;
> VALUES (myvar1);
  5

-- Set a SQL variable back to DEFAULT
> SET VARIABLE myvar1 = DEFAULT;
> VALUES (myvar1);
  7

-- Set a SQL variable to the result of a scalar subquery.
> SET VARIABLE myvar1 = (SELECT max(c1) FROM VALUES(1), (2) AS T(c1));
> VALUES (myvar1);
  2

-- Set multiple variables from a query
> SET VAR (myvar1, myvar2) = (VALUES(10, 'world'));
> VALUES (myvar1, myvar2);
  10   world

-- Set multiple variables from expressions
> SET VAR myvar1 = 11, myvar2 = 'hello';
> VALUES (myvar1, myvar2);
  11   hello

-- Set multiple variables based on a query
> SET VARIABLE (myvar1, myvar2)
    = (SELECT max(c1), CAST(min(c1) AS STRING) FROM VALUES(1), (2) AS T(c1));
> VALUES (myvar1, myvar2);
  2    1

-- Assign NULLs on empty query
> SET VAR (myvar1, myvar2)
    = (SELECT max(c1), CAST(min(c1) AS STRING) FROM VALUES(1), (2) AS T(c1) HAVING max(c1) = 0);
> VALUES (myvar1, myvar2);
  NULL  NULL

-- Using a variable with an IDENTIFIER clause
> DECLARE colname STRING;
> SET VAR colname = 'c1';
> SELECT IDENTIFIER(colname) FROM VALUES(1, 2) AS T(c1, c2);
  1

> SET VARIABLE colname = 'c2';
> SELECT IDENTIFIER(colname) FROM VALUES(1, 2) AS T(c1, c2);
  2

-- Variable defaults are recomputed
> DECLARE VARIABLE val DEFAULT RAND();
> SELECT val;
  0.1234...

> SET VARIABLE val = DEFAULT;
> SELECT val;
  0.9876...