MySQL存储过程

1.参数验证和错误反馈
mysql 5.5开始引入SIGNAL语句,通过它可以反馈存储过程的数据验证错误.在5.5之前的版本,只能通过其它方法变通解决.
SIGNAL语句的语法:
SIGNAL SQLSTATE [value] sqlstate_value

[SET MESSAGE_TEXT = message[,mysql_ERRNO = mysql_error_number]];

例子:

USE ap;

DROP PROCEDURE IF EXISTS insert_invoice;

DELIMITER //

CREATE PROCEDURE insert_invoice
(
  vendor_id_param        INT,
  invoice_number_param   VARCHAR(50),
  invoice_date_param     DATE,
  invoice_total_param    DECIMAL(9,2),
  terms_id_param         INT,
  invoice_due_date_param DATE
)
BEGIN
  DECLARE terms_id_var           INT;
  DECLARE invoice_due_date_var   DATE;  
  DECLARE terms_due_days_var     INT;

  -- Validate paramater values
  IF invoice_total_param < 0 THEN     SIGNAL SQLSTATE '22003'       SET MESSAGE_TEXT = 'The invoice_total column must be a positive number.',        MYSQL_ERRNO = 1264;   ELSEIF invoice_total_param >= 1000000 THEN
    SIGNAL SQLSTATE '22003'
      SET MESSAGE_TEXT = 'The invoice_total column must be less than 1,000,000.', 
      MYSQL_ERRNO = 1264;
  END IF;

  -- Set default values for parameters
  IF terms_id_param IS NULL THEN
    SELECT default_terms_id INTO terms_id_var
    FROM vendors WHERE vendor_id = vendor_id_param;
  ELSE
    SET terms_id_var = terms_id_param;
  END IF;
  IF invoice_due_date_param IS NULL THEN
    SELECT terms_due_days INTO terms_due_days_var
      FROM terms WHERE terms_id = terms_id_var;
    SELECT DATE_ADD(invoice_date_param, INTERVAL terms_due_days_var DAY) 
      INTO invoice_due_date_var;
  ELSE
    SET invoice_due_date_var = invoice_due_date_param;
  END IF;

  INSERT INTO invoices
         (vendor_id, invoice_number, invoice_date, 
          invoice_total, terms_id, invoice_due_date)
  VALUES (vendor_id_param, invoice_number_param, invoice_date_param, 
          invoice_total_param, terms_id_var, invoice_due_date_var);
END//

DELIMITER ;

-- test
CALL insert_invoice(34, 'ZXA-080', '2012-01-18', 14092.59, 
                    3, '2012-03-18');
CALL insert_invoice(34, 'ZXA-082', '2012-01-18', 14092.59,
                    NULL, NULL);

-- this statement raises an error
CALL insert_invoice(34, 'ZXA-083', '2012-01-18', -14092.59,
                    NULL, NULL);

-- clean up
SELECT * FROM invoices WHERE invoice_id >= 115;

DELETE FROM invoices WHERE invoice_id >= 115;

2.使用动态SQL
通过PREPARE,EXECUTE,DEALLOCATE等语句可以在存储过程中创建动态SQL.

例子:

USE ap;

DROP PROCEDURE IF EXISTS select_invoices;

DELIMITER //

CREATE PROCEDURE select_invoices
(
  min_invoice_date_param   DATE,
  min_invoice_total_param  DECIMAL(9,2)
)
BEGIN
  DECLARE select_clause VARCHAR(200);
  DECLARE where_clause  VARCHAR(200);

  SET select_clause = "SELECT invoice_id, invoice_number, 
                       invoice_date, invoice_total 
                       FROM invoices ";      
  SET where_clause =  "WHERE ";

  IF min_invoice_date_param IS NOT NULL THEN
    SET where_clause = CONCAT(where_clause, 
       " invoice_date > '", min_invoice_date_param, "'");
  END IF;

  IF min_invoice_total_param IS NOT NULL THEN
    IF where_clause != "WHERE " THEN
      SET where_clause = CONCAT(where_clause, "AND ");
    END IF;
    SET where_clause = CONCAT(where_clause, 
       "invoice_total > ", min_invoice_total_param);
  END IF;

  IF where_clause = "WHERE " THEN
    SET @dynamic_sql = select_clause;
  ELSE
    SET @dynamic_sql = CONCAT(select_clause, where_clause);    
  END IF;

  PREPARE select_invoices_statement
  FROM @dynamic_sql;

  EXECUTE select_invoices_statement;

  DEALLOCATE PREPARE select_invoices_statement;  
END//

DELIMITER ;

CALL select_invoices('2011-07-25', 100);

CALL select_invoices('2011-07-25', NULL);

CALL select_invoices(NULL, 1000);

CALL select_invoices(NULL, NULL);

3.使用游标

游标定义:
DECLARE cursor_name CURSOR FOR select_statement;
游标错误控制:
DECLARE CONTINUE HANDLER FOR NOT FOUND handler_statement;
打开游标:
OPEN cursor_name;
获取游标行的值并保存到一系列变量中:
FETCH cursor_name INTO variable1[, variable2][, variable3]…;
关闭游标:
CLOSE cursor_name;

例子:

USE ap;

DROP PROCEDURE IF EXISTS test;

DELIMITER //

CREATE PROCEDURE test()
BEGIN
  DECLARE invoice_id_var    INT;
  DECLARE invoice_total_var DECIMAL(9,2);  
  DECLARE row_not_found     TINYINT DEFAULT FALSE;
  DECLARE update_count      INT DEFAULT 0;

  DECLARE invoices_cursor CURSOR FOR
    SELECT invoice_id, invoice_total  FROM invoices
    WHERE invoice_total - payment_total - credit_total > 0;

  DECLARE CONTINUE HANDLER FOR NOT FOUND
    SET row_not_found = TRUE;

  OPEN invoices_cursor;

  WHILE row_not_found = FALSE DO
    FETCH invoices_cursor INTO invoice_id_var, invoice_total_var;

    IF invoice_total_var > 1000 THEN
      UPDATE invoices
      SET credit_total = credit_total + (invoice_total * .1)
      WHERE invoice_id = invoice_id_var;

      SET update_count = update_count + 1;
    END IF;
  END WHILE;

  CLOSE invoices_cursor;

  SELECT CONCAT(update_count, ' row(s) updated.');

END//

DELIMITER ;

CALL test();

4.事务控制

先定义一个sql_error标识,然后对SQLEXCEPTION进行捕捉,最后根据sql_error标识来控制事务的commit或rollback.

看例子:

USE ap;

DROP PROCEDURE IF EXISTS test;

DELIMITER //

CREATE PROCEDURE test()
BEGIN
  DECLARE sql_error INT DEFAULT FALSE;
  
  DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
    SET sql_error = TRUE;

  START TRANSACTION;
  
  INSERT INTO invoices
  VALUES (115, 34, 'ZXA-080', '2011-06-30', 
          14092.59, 0, 0, 3, '2011-09-30', NULL);

  INSERT INTO invoice_line_items 
  VALUES (115, 1, 160, 4447.23, 'HW upgrade');
  
  INSERT INTO invoice_line_items 
  VALUES (115, 2, 167, 9645.36, 'OS upgrade');
  
  IF sql_error = FALSE THEN
    COMMIT;
    SELECT 'The transaction was committed.';
  ELSE
    ROLLBACK;
    SELECT 'The transaction was rolled back.';
  END IF;
END//

DELIMITER ;

CALL test();

-- Check data
SELECT invoice_id, invoice_number
FROM invoices WHERE invoice_id = 115;

SELECT invoice_id, invoice_sequence, line_item_description
FROM invoice_line_items WHERE invoice_id = 115;

-- Clean up
DELETE FROM invoice_line_items WHERE invoice_id = 115;
DELETE FROM invoices WHERE invoice_id = 115;