IS EMPTY

This is a translation reference to convert the Oracle IS EMPTY statement to Snowflake

This section is a work in progress; information may change in the future.

Description

Use the IS [NOT] EMPTY conditions to test whether a specified nested table is empty, regardless whether any elements of the collection are NULL. (Documentation).

Oracle syntax

nested_table IS [ NOT ] EMPTY

Sample Source Patterns

Oracle

The following example shows the usage of the IS EMPTY statement. The statement is applied over a nested table which uses a UDT as the definition type. The output shows the name of the employees who do not have a phone number.

IN -> Oracle_01.sql
CREATE TYPE phone_number_type AS OBJECT (phone_number VARCHAR2(30));
/

CREATE TYPE phone_number_list AS TABLE OF phone_number_type;

CREATE TABLE employee (
    emp_id NUMBER,
    emp_name VARCHAR2(50),
    phone_numbers_col phone_number_list
) NESTED TABLE phone_numbers_col STORE AS nested_tab return as value;

INSERT INTO employee VALUES (
    1,
    'John Doe',
    phone_number_list(phone_number_type('1234567890'))
);
/

INSERT INTO employee VALUES (
    2,
    'Jane Smith',
    phone_number_list()
);

SELECT emp_name
FROM employee
WHERE phone_numbers_col IS EMPTY;

Snowflake

The Snowflake query shown below is the equivalence of the functionality of the IS EMPTY statement. Particularly, the IS EMPTY statement has a difference between a NULL and an EMPTY object.

Notice that the User-Defined Types are transformed to a VARIANT. The VARIANT type in Snowflake is able to store objects and arrays. Since a nested table is a sequence of information, the ARRAY type is the most suitable type to redefine them and verify is the object ARRAY is empty.

The ARRAY_SIZE equivalent solution also allows to ask for nullability of the nested table (transformed to VARIANT). In other words, the VARIANT type can also store NULLs and empty ARRAYs.

OUT -> Oracle_01.sql
!!!RESOLVE EWI!!! /*** SSC-EWI-0056 - CUSTOM TYPES ARE NOT SUPPORTED IN SNOWFLAKE BUT REFERENCES TO THIS CUSTOM TYPE WERE CHANGED TO VARIANT ***/!!!
CREATE TYPE phone_number_type AS OBJECT (phone_number VARCHAR2(30))
;

!!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'NESTED TABLE' NODE ***/!!!

CREATE TYPE phone_number_list AS TABLE OF phone_number_type;

CREATE OR REPLACE TABLE employee (
    emp_id NUMBER(38, 18) /*** SSC-FDM-0006 - NUMBER TYPE COLUMN MAY NOT BEHAVE SIMILARLY IN SNOWFLAKE. ***/,
    emp_name VARCHAR(50),
    phone_numbers_col VARIANT !!!RESOLVE EWI!!! /*** SSC-EWI-0062 - CUSTOM TYPE 'phone_number_list' USAGE CHANGED TO VARIANT ***/!!!
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"oracle"}}'
;

CREATE OR REPLACE VIEW PUBLIC.employee_view
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "" }}'
AS
SELECT
    emp_id,
    emp_name,
    phone_numbers_col
FROM
    employee;

INSERT INTO employee
VALUES (
    1,
    'John Doe',
    phone_number_list(phone_number_type('1234567890') !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'phone_number_type' NODE ***/!!!) !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'phone_number_list' NODE ***/!!!
);

INSERT INTO employee
VALUES (
    2,
    'Jane Smith',
    phone_number_list() !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'phone_number_list' NODE ***/!!!
);

SELECT emp_name
FROM
    employee
WHERE
    ARRAY_SIZE( phone_numbers_col) = 0;

Other possible combinations

DescriptionOracleSnowflake

Ask for a IS NOT EMPTY

(...)
WHERE phone_numbers_col IS NOT EMPTY;
(...)
WHERE ARRAY_SIZE(phone_numbers_col) != 0;

Ask for NULL instead of EMPTY

(...)
WHERE phone_numbers_col IS NULL;
(...)
WHERE ARRAY_SIZE(phone_numbers_col) IS NULL;