Categories:

Conditional expression functions , Semi-structured and structured data functions (Type Predicates)

IS_NULL_VALUE¶

Returns TRUE if its VARIANT argument is a JSON null value.

Important

The JSON null value is distinct from the SQL NULL value.

This function returns TRUE only for JSON null values, not SQL NULL values. The difference is shown in the first and third rows in the output for the example below.

A missing JSON value is converted to a SQL NULL value, for which IS_NULL_VALUE returns NULL. The 4th column in the output for the example below shows this.

This function is different from the IS [ NOT ] NULL function.

See also:

IS_<object_type>

Syntax¶

IS_NULL_VALUE( <variant_expr> )
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Arguments¶

variant_expr

An expression that evaluates to a value of type VARIANT.

Returns¶

This function returns a value of type BOOLEAN or NULL:

  • Returns TRUE for a JSON null value.

  • Returns FALSE for a non-null JSON value.

  • Returns NULL for a SQL NULL value.

Examples¶

This example uses the IS_NULL_VALUE function. First, create a table with a VARIANT column:

CREATE OR REPLACE TABLE test_is_null_value_function (
  variant_value VARIANT);
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Insert a string value into the column using the PARSE_JSON function:

INSERT INTO test_is_null_value_function (variant_value)
  (SELECT PARSE_JSON('"string value"'));
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Note

The PARSE_JSON function returns a VARIANT value.

Insert a JSON null value into the column:

INSERT INTO test_is_null_value_function (variant_value)
  (SELECT PARSE_JSON('null'));
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Insert an empty object into the column:

INSERT INTO test_is_null_value_function (variant_value)
  (SELECT PARSE_JSON('{}'));
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Insert two rows with JSON name/value pairs into the VARIANT column :

INSERT INTO test_is_null_value_function (variant_value)
  (SELECT PARSE_JSON('{"x": null}'));

INSERT INTO test_is_null_value_function (variant_value)
  (SELECT PARSE_JSON('{"x": "foo"}'));
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Insert a NULL into the column:

INSERT INTO test_is_null_value_function (variant_value)
  (SELECT PARSE_JSON(NULL));
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Query the table:

SELECT variant_value,
       variant_value:x value_of_x,
       IS_NULL_VALUE(variant_value) is_variant_value_a_json_null,
       IS_NULL_VALUE(variant_value:x) is_x_a_json_null,
       IS_NULL_VALUE(variant_value:y) is_y_a_json_null
  FROM test_is_null_value_function;
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+----------------+------------+------------------------------+------------------+------------------+
| VARIANT_VALUE  | VALUE_OF_X | IS_VARIANT_VALUE_A_JSON_NULL | IS_X_A_JSON_NULL | IS_Y_A_JSON_NULL |
|----------------+------------+------------------------------+------------------+------------------|
| "string value" | NULL       | False                        | NULL             | NULL             |
| null           | NULL       | True                         | NULL             | NULL             |
| {}             | NULL       | False                        | NULL             | NULL             |
| {              | null       | False                        | True             | NULL             |
|   "x": null    |            |                              |                  |                  |
| }              |            |                              |                  |                  |
| {              | "foo"      | False                        | False            | NULL             |
|   "x": "foo"   |            |                              |                  |                  |
| }              |            |                              |                  |                  |
| NULL           | NULL       | NULL                         | NULL             | NULL             |
+----------------+------------+------------------------------+------------------+------------------+

In the query results:

  • The variant_value column shows six rows of inserted VARIANT values.

  • The value_of_x column shows the JSON value for the name x in each row.

  • The is_variant_value_a_json_null column returns the results of the IS_NULL_VALUE function for the VARIANT value in each row.

  • The is_x_a_json_null column returns the results of the IS_NULL_VALUE function for the name x in each row. Rows without an x name return NULL.

  • The is_y_a_json_null column returns the results of the IS_NULL_VALUE function for the name y in each row. Because there is no matching y name in any row, all of the rows return NULL.

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