CASE

Translation reference to convert Transact-SQL Case expression to Snowflake Scripting

Important Notice: Migration of Documentation Website

Please be advised that our documentation website is currently undergoing a migration to a new platform. To ensure you have access to the most up-to-date information, we kindly request that you visit our new documentation website located at:

Official Snowflake Snowconvert Documentation

For any immediate assistance or if you encounter any issues, please contact our support team at [email protected].

Thank you for your understanding.

Applies to

• SQL Server

• Azure Synapse Analytics

Some parts in the output code are omitted for clarity reasons.

Description

Transact-SQL has two possible formats of the Case expression. both of them for the purpose of evaluating expressions and conditionally obtaining results. The first one refers to a Simple Case Expression that will evaluate if an input_expression matches one or more of the when_expression. The second one will evaluate each Boolean_expression independently. The else clause is supported in both formats.

According to the official Transact-SQL Case documentation:

CASE can be used in any statement or clause that allows a valid expression. For example, you can use CASE in statements such as SELECT, UPDATE, DELETE and SET, and in clauses such as select_list, IN, WHERE, ORDER BY, and HAVING.

For more information regarding Transact-SQL Case, check here.

-- Simple CASE expression:   
CASE input_expression   
     WHEN when_expression THEN result_expression [ ...n ]   
     [ ELSE else_result_expression ]   
END   

-- Searched CASE expression:  
CASE  
     WHEN boolean_expression THEN result_expression [ ...n ]   
     [ ELSE else_result_expression ]   
END

Note: Transact-SQL allows to optionally encapsulate the input_expression and the boolean_expression in parentheses; Snowflake Scripting too.

Sample Source Patterns

The following examples detail two scenarios where the Case expression can be used and their differences from Snowflake Scripting.

Select using Case

Transact-SQL

Simple CASE

IN -> SqlServer_01.sql

CREATE OR ALTER PROCEDURE SelectCaseDemoProcedure
AS
      SELECT TOP 10
          LOGINID,
          CASE (MARITALSTATUS)
              WHEN 'S' THEN 'SINGLE'
              WHEN 'M' THEN 'MARIED'
              ELSE 'OTHER'
          END AS status
      FROM HUMANRESOURCES.EMPLOYEE;
GO

EXEC SelectCaseDemoProcedure;

Searched CASE

Result

Snowflake Scripting

Note that in this scenario there are no differences regarding the Case expression itself.

The declaration and assignment of the res variable is in order to demonstrate the functional equivalence between both languages. It does not appear in the actual output.

Simple CASE

OUT -> SqlServer_01.sql

CREATE OR REPLACE PROCEDURE SelectCaseDemoProcedure ()
RETURNS TABLE()
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
      DECLARE
            ProcedureResultSet RESULTSET;
      BEGIN
            ProcedureResultSet := (
            SELECT TOP 10
                  LOGINID,
                CASE (MARITALSTATUS)
                    WHEN 'S' THEN 'SINGLE'
                    WHEN 'M' THEN 'MARIED'
                    ELSE 'OTHER'
                END AS status
            FROM
                  HUMANRESOURCES.EMPLOYEE);
            RETURN TABLE(ProcedureResultSet);
      END;
$$;

CALL SelectCaseDemoProcedure();

Searched CASE

Result

Set using Case

The AdventureWorks2019 database was used in both languages to obtain the same results.

Transact-SQL

Simple Case

IN -> SqlServer_03.sql

CREATE OR ALTER PROCEDURE SetCaseDemoProcedure
AS
    DECLARE @value INT;
    DECLARE @result INT;
    SET @value = 5;
    
    SET @result =
        CASE @value
            WHEN 1 THEN @value * 10
            WHEN 3 THEN @value * 20
            WHEN 5 THEN @value * 30
            WHEN 7 THEN @value * 40
            ELSE -1
        END;
    
    RETURN @result
GO

DECLARE @result INT;
EXEC @result = SetCaseDemoProcedure;
PRINT @result;

Searched Case

Result

Snowflake Scripting

Snowflake Scripting does not allow to set a case expression directly to a variable. Both Transact-SQL Case expression formats translate to the following grammar in Snowflake Scripting.

SimpleCase

OUT -> SqlServer_03.sql

CREATE OR REPLACE PROCEDURE SetCaseDemoProcedure ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
    DECLARE
        VALUE INT;
        RESULT INT;
    BEGIN
         
         
        VALUE := 5;
        CASE (:VALUE)
            WHEN 1 THEN
                RESULT := :VALUE * 10;
            WHEN 3 THEN
                RESULT := :VALUE * 20;
            WHEN 5 THEN
                RESULT := :VALUE * 30;
            WHEN 7 THEN
                RESULT := :VALUE * 40;
            ELSE
                RESULT := -1;
        END;
        RETURN :RESULT;
    END;
$$;

DECLARE
    RESULT INT;
BEGIN
    CALL SetCaseDemoProcedure();
    !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'Print' NODE ***/!!!
    PRINT @result;
END;

Searched Case

Result

Known Issues

No issues were found.

Related EWIs

1. SSC-EWI-0073: Pending Functional Equivalence Review.