How to write an equivalent IF ELSE adhoc sql query in Snowflake - if-statement

Question

I am trying to create a Snowflake equivalent to the below T-SQL based adhoc query.
**T-SQL version**
Declare #i int = 0;
If(#i = 0)
PRINT '0';
Else
Begin
PRINT '1'
RETURN;
PRINT '2'
End
**Snowflake version**
Set i = 0;
If($i = 0)
Select '0';
Else
Begin
Select '1'
RETURN;
Select '2'
End
When I am running the Snowflake query from the Snowflake Web UI, I am getting an error as
SQL compilation error : syntax error line 1 at position 0 unexpected 'IF'
I have searched the snowflake documentation and did not find helpful documentation for:
If Else
Begin End
Return
Any help would be appreciated.
Thank you.

Answer 1

Snowflake does not support conditional T-SQL statements. It does support conditional expressions within a query.
For conditional statement execution, consider using Snowflake's stored procedures with embedded JavaScript if the use of conditional expressions is inadequate for your needs.
A very trivial example of a stored procedure, illustrating a conditional query execution upon call:
CREATE OR REPLACE PROCEDURE stored_proc_example(TEST_VALUE INTEGER)
RETURNS VARCHAR
LANGUAGE JAVASCRIPT
AS
$$
// Declaring SQL statement(s) to execute later
var command_1 = "SELECT 1";
var command_2 = "SELECT 2";
if (TEST_VALUE === 0) {
var stmt = snowflake.createStatement({ sqlText: command_1 });
var rs = stmt.execute();
// Omitted: Perform logic with 'rs' rows to prepare a return value
return '1';
} else {
var stmt = snowflake.createStatement({ sqlText: command_2 });
var rs = stmt.execute();
// Omitted: Perform logic with 'rs' rows to prepare a return value
return '2';
}
$$
;
Run as:
SET i=0;
CALL stored_proc_example($i);
SET i=1;
CALL stored_proc_example($i);

Answer 2

Snowflake Scripting introduced anonymous block and Branching constructs:
DECLARE
i INT DEFAULT 0;
BEGIN
IF (i = 0) THEN
RETURN 'zero';
ELSE
RETURN 'non-zero';
END IF;
END;
or:
BEGIN
LET i INT := 0;
IF (i = 0) THEN
RETURN 'zero';
ELSE
RETURN 'non-zero';
END IF;
END;
Further reading: Working with Variables

Answer 3

In Snowflake you can use CASE WHEN statements for this. Here's the documentation.

Answer 4

You can try with snowflake scripting and change your accordingly
set
stmt = $$
begin
let i := 1;
case when (i=0) then
return 0;
when (i=1 ) then
return '1 ';
else
return '2';
end ;
end;
$$;
execute immediate $stmt;

Answer 5

SELECT student_name 'Student Name',
CASE grade
WHEN 'A' THEN 'Excellent'
WHEN 'B' THEN 'Good'
WHEN 'C' THEN 'Average'
WHEN 'D' THEN 'Poor'
WHEN 'F' THEN 'Fail'
ELSE 'N/A'
END 'Grade'
FROM student
-- Output