-- 10/21
tee 2024_10_21_sql_log.txt
use toyu

-- Redefine the delimiter to end the procedure.
-- default delimiter: ;
DELIMITER //

-- IN: pass by value; 
--  OUT: copy out when exiting.
CREATE OR REPLACE PROCEDURE deptInfo(IN dCode VARCHAR(4), OUT numFaculty INT)
BEGIN   -- dcode: ‘CSCI’; numFaculty: Null
   --  Display some information.
   SELECT d.deptName, d.SchoolCode, t1.n_majors, t2.n_minors
   FROM toyu.department AS d INNER JOIN
      (SELECT COUNT(stuId) AS n_majors
      FROM toyu.student
      WHERE major = dCode) AS t1 INNER JOIN
      (SELECT COUNT(stuId) AS n_minors
      FROM toyu.student
      WHERE minor = dCode) AS t2
   WHERE d.deptCode = dCode;

   -- MySQL does not direct sending output to console.
   -- It is necessary to use a SQL statement.
   SELECT 'Debuggin comment can be put here.';
   SELECT CONCAT('Faculty in the department: ', dCode) AS faculty;

   SELECT *
   FROM faculty AS f
   WHERE f.deptCode = dCode;

   SELECT COUNT(f.facId) INTO numFaculty
   FROM toyu.faculty AS f
   WHERE f.deptCode = dCode;
END //

DELIMITER ;

SHOW CREATE PROCEDURE deptInfo;

SET @numFaculty = 0;
SET @dCode = 'CSCI';
CALL deptInfo(@dCode, @numFaculty);
SELECT @dCode, @numFaculty;

CALL deptInfo('CSCI', @numFaculty);
SELECT 'CSCI', @numFaculty;

CALL deptInfo('CSCI', 4);
SELECT 'CSCI', @numFaculty;
ERROR 1414 (42000): OUT or INOUT argument 2 for routine toyu.deptInfo is not a variable or NEW pseudo-variable in BEFORE trigger
MariaDB [toyu]> SELECT 'CSCI', @numFaculty;

SET @dCode = 'ITEC';
CALL deptInfo(@dCode, @numFaculty);
SELECT @dCode, @numFaculty;

DROP PROCEDURE deptInfo;



-- A simple function
DELIMITER //

-- pragma 

-- mode: IN only; OUT and IN OUT not acceptable in a function


CREATE OR REPLACE FUNCTION n_major(dCode varchar(4)) RETURNS INT
READS SQL DATA
BEGIN
   DECLARE count INT DEFAULT 0;

   SELECT COUNT(*) INTO count
   FROM toyu.student
   WHERE major = dCode;

   RETURN count;
END //

DELIMITER ;

SHOW CREATE FUNCTION n_major;

SELECT n_major('CSCI');
SELECT n_major('ITEC');


-- A simple function
DELIMITER //

CREATE OR REPLACE FUNCTION n_major(dCode varchar(4)) RETURNS INT
READS SQL DATA
BEGIN
   DECLARE count INT DEFAULT 0;

   SELECT COUNT(*)
   FROM toyu.student
   WHERE major = dCode;

   RETURN count;
END //

DELIMITER ;
ERROR 1415 (0A000): Not allowed to return a result set from a function