Cursor with IF statement

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

This pattern defines a function that conditionally uses a cursor to fetch and return a value based on an IF statement.

Components:

1. Function Declaration:

   • CREATE FUNCTION functionName(parameters) RETURN returnType

   • Declares the function with input parameters and the return type.

2. Cursor Declaration:

   • CURSOR cursorName IS SELECT singleColumn FROM ... WHERE ... [AND col1 = localVar1];

   • Defines a cursor to select a single column from a table with optional filtering conditions.

3. Variable Declaration:

   • Declares variables, including the return variable.

4. BEGIN-END Block with IF Statement:

   • Variables assignment.

   • Check if a condition is true.

   • If true, opens the cursor, fetches the result into the return variable, closes the cursor, and returns the fetched value. (The cursor can also be opened in the ELSE block and must meet the same conditions)

   • The ELSE Block is optional, if it exists, it should only contain a single statement that can be an assignment or a RETURN statement.

The variables are transformed into a common table expression (CTE). As well as the query within the cursor to which, in addition, the FETCH FIRST 1 ROW ONLY clause is added to simulate the FETCH CURSOR behavior.

IF/ELSE statement can be handled using the CASE EXPRESSION inside the select allowing conditionals inside the queries. RETURN statement is transformed to the final select..

Queries

Oracle

IN -> Oracle_01.sql

CREATE OR REPLACE FUNCTION func1 (
   company_          IN NUMBER) RETURN NUMBER
IS
   CURSOR getmaxperiod IS
      SELECT max(col2)
      FROM   table1;
   max_period_               NUMBER := 12;
BEGIN
   IF 1 = 1 THEN
      OPEN   getmaxperiod;
      FETCH  getmaxperiod INTO max_period_ ;
      CLOSE  getmaxperiod;
      RETURN max_period_;
   ELSE
      RETURN NULL;
   END IF;
END func1;

Snowflake

OUT -> Oracle_01.sql

CREATE OR REPLACE FUNCTION func1 (company_ NUMBER(38, 18))
RETURNS NUMBER(38, 18)
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "09/06/2024" }}'
AS
$$
   WITH declaration_variables_cte0 AS
   (
      SELECT
         12 AS
         max_period_
   ),
   declaration_variables_cte1 AS
   (
      SELECT
         CASE
            WHEN 1 = 1
               THEN (
               SELECT max(col2)
               FROM   table1
               FETCH FIRST 1 ROW ONLY)
            ELSE NULL
         END AS max_period_
      FROM
         declaration_variables_cte0
   )
   SELECT
      max_period_
   FROM
      declaration_variables_cte1
$$;

Result

FUNC2(0)      |
--------------+
NULL          |

FUNC2(1)      |
--------------+
33            |

Oracle

IN -> Oracle_02.sql

CREATE OR REPLACE FUNCTION func2(
   company_          IN NUMBER) RETURN NUMBER
IS
   CURSOR getmaxperiod IS
      SELECT max(col2)
      FROM   table1;
   max_period_               NUMBER := 1;
BEGIN
   max_period_:= 2;
   IF company_ = 1 THEN
      RETURN max_period_ * 2;
   ELSE
      OPEN   getmaxperiod;
      FETCH  getmaxperiod INTO max_period_ ;
      CLOSE  getmaxperiod;
      RETURN max_period_;
   END IF;
END func2;

Snowflake

OUT -> Oracle_02.sql

CREATE OR REPLACE FUNCTION func2 (company_ NUMBER(38, 18))
RETURNS NUMBER(38, 18)
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "09/06/2024" }}'
AS
$$
   WITH declaration_variables_cte0 AS
   (
      SELECT
         1 AS
         max_period_
   ),
   declaration_variables_cte1 AS
   (
      SELECT
         2 AS
         max_period_
      FROM
         declaration_variables_cte0
   ),
   declaration_variables_cte2 AS
   (
      SELECT
         CASE
            WHEN company_ = 1
               THEN max_period_ * 2
            ELSE (
            SELECT max(col2)
            FROM   table1
            FETCH FIRST 1 ROW ONLY)
         END AS max_period_
      FROM
         declaration_variables_cte1
   )
   SELECT
      max_period_
   FROM
      declaration_variables_cte2
$$;

Result

FUNC2(0)      |
--------------+
33            |

FUNC2(1)      |
--------------+
2             |

Oracle

IN -> Oracle_03.sql

CREATE OR REPLACE FUNCTION func3 (
   company_          IN NUMBER) RETURN NUMBER
IS
   CURSOR getmaxperiod IS
      SELECT max(col2)
      FROM   table1;
   max_period_               NUMBER := 0;
BEGIN
   IF company_ = 1 THEN
      OPEN   getmaxperiod;
      FETCH  getmaxperiod INTO max_period_ ;
      CLOSE  getmaxperiod;
   END IF;
   RETURN max_period_;
END func10;

Snowflake

OUT -> Oracle_03.sql

CREATE OR REPLACE FUNCTION func3 (company_ NUMBER(38, 18))
RETURNS NUMBER(38, 18)
LANGUAGE SQL
COMMENT = '{ "origin": "sf_sc", "name": "snowconvert", "version": {  "major": 0,  "minor": 0,  "patch": "0" }, "attributes": {  "component": "oracle",  "convertedOn": "09/06/2024" }}'
AS
$$
   WITH declaration_variables_cte0 AS
   (
      SELECT
         0 AS
         max_period_
   ),
   declaration_variables_cte1 AS
   (
      SELECT
         CASE
            WHEN company_ = 1
               THEN (
               SELECT max(col2)
               FROM   table1
               FETCH FIRST 1 ROW ONLY)
            ELSE max_period_
         END AS max_period_
      FROM
         declaration_variables_cte0
   )
   SELECT
      max_period_
   FROM
      declaration_variables_cte1
$$;

Result

FUNC2(0)      |
--------------+
0             |

FUNC2(1)      |
--------------+
33            |

Known Issues

No issues were found.

Related EWIS

No EWIs related.