WHILE

Translation reference to convert Transact-SQL While Statement to Snowflake Scripting

Applies to

• SQL Server

• Azure Synapse Analytics

Description

The While statement allows an SQL statement or a block of statements to be repeatedly executed as long as the specified condition is true. The execution of statements in the WHILE loop can be controlled from inside the loop with the BREAK and CONTINUE keywords.

For more information for Transact-SQL While, check here.

WHILE Boolean_expression   
     { sql_statement | statement_block | BREAK | CONTINUE }

Note: To define a statement block, use the control-of-flow keywords BEGIN and END.

Sample Source Patterns

Basic source pattern code

Transact-SQL

The following code refers to a While Loop in Transact-SQL that iterates the @Iteration variable and controls the flow of the loop to terminate when the value of @Iteration equals 10.

Statements after the CONTINUE keyword will not be executed.

While

IN -> SqlServer_01.sql

CREATE OR ALTER PROCEDURE WhileDemoProcedure
AS
    DECLARE @iteration INT;
    SET @iteration = 1;
    
    WHILE @iteration < 100
    BEGIN
        IF @iteration = 10
            BREAK;
        ELSE
            BEGIN
                SET @iteration = @iteration + 1;
                CONTINUE;
                SET @iteration = 2 * @iteration;
            END;
    END;
    RETURN @iteration;
GO



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

Result

|iteration|
|---------|
|10       |

Snowflake Scripting

As well as Transact-SQL, in Snowflake Scripting the statements after the CONTINUE keyword will not be executed.

Notice that in Snowflake Scripting it is not necessary to use the BEGIN and END keywords to define a statement block, however it can be used if required.

While

OUT -> SqlServer_01.sql

CREATE OR REPLACE PROCEDURE WhileDemoProcedure ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
    DECLARE
        ITERATION INT;
    BEGIN
         
        ITERATION := 1;
        WHILE (:ITERATION < 100) LOOP
            IF (:ITERATION = 10) THEN
                BREAK;
            ELSE
                BEGIN
                    ITERATION := :ITERATION + 1;
                    CONTINUE;
                    ITERATION := 2 * :ITERATION;
                END;
            END IF;
        END LOOP;
        RETURN :ITERATION;
    END;
$$;

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

Loop keyword

Snowflake Scripting allows to use LOOP keyword instead of DO and the END LOOP expression instead of END WHILE .

WHILE (Boolean_expression) LOOP
    -- statement or statement block
END LOOP;

Result

|Iteration|
|---------|
|10       |

While with empty body Source Pattern

Transact-SQL

Please note this example was written while the IF ELSE statement was not supported, the differences in the results should disappear when support for the statement is implemented.

Query

IN -> SqlServer_02.sql

CREATE OR ALTER PROCEDURE WhileEmptyBodyProc
AS
BEGIN
    DECLARE @MyVar INT;
    SET @MyVar = 1;
    WHILE (@MyVar < 100)
        BEGIN
            IF @MyVar < 50
                SET @MyVar *= 5;
            ELSE
                SET @MyVar *= 3;
        END;
    RETURN @MyVar;
END;

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

Result

|result|
|------|
|125   |

Snowflake Scripting

This statement can not have an empty body in Snowflake Scripting, to solve this cases a default BREAK statement is added when an empty body is detected.

Query

OUT -> SqlServer_02.sql

CREATE OR REPLACE PROCEDURE WhileEmptyBodyProc ()
RETURNS VARCHAR
LANGUAGE SQL
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},{"attributes":{"component":"transact"}}'
EXECUTE AS CALLER
AS
$$
    DECLARE
        MYVAR INT;
        RESULT INT;
    BEGIN
        BEGIN
             
            MYVAR := 1;
            WHILE (:MYVAR < 100) LOOP
                IF (:MYVAR < 50) THEN
                    MYVAR := MYVAR * 5;
                ELSE
                    MYVAR := MYVAR * 3;
                END IF;
            END LOOP;
            RETURN :MYVAR;
        END;
         
        CALL WhileEmptyBodyProc();
        !!!RESOLVE EWI!!! /*** SSC-EWI-0073 - PENDING FUNCTIONAL EQUIVALENCE REVIEW FOR 'PRINT' NODE ***/!!!
        PRINT @result;
    END;
$$;

Result

|result|
|------|
|1     |

WHILE statement outside routines (functions and procedures)

Unlike Transact-SQL, Snowflake does not support executing isolated statements like WHILE outside routines like functions or procedures. For this scenario, the statement should be encapsulated in an anonymous block, as shown in the following example.

Transact-SQL

IN -> SqlServer_03.sql

DECLARE @iteration INT;
SET @iteration = 1;
 
WHILE @iteration < 100
BEGIN
    IF @iteration = 10
        BREAK;
    ELSE
        BEGIN
            SET @iteration = @iteration + 1;
            CONTINUE;
            SET @iteration = 2 * @iteration;
        END;
    END;

Snowflake Scripting

OUT -> SqlServer_03.sql

DECLARE
    ITERATION INT;
BEGIN
    ITERATION := 1;
    WHILE (:ITERATION < 100) LOOP
        IF (:ITERATION = 10) THEN
            BREAK;
        ELSE
            BEGIN
                ITERATION := :ITERATION + 1;
                CONTINUE;
                ITERATION := 2 * :ITERATION;
            END;
        END IF;
    END LOOP;
END;

Known Issues

No issues were found.

Related EWIs

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