rails generate rspec:install

List All rails Process:  $   ps auxw | grep rails

Kill Process:  $kill -9 1563

This guide covers different ways to retrieve data from the database using Active Record. By referring to this guide, you will be able to:

• Find records using a variety of methods and conditions
• Specify the order, retrieved attributes, grouping, and other properties of the found records
• Use eager loading to reduce the number of database queries needed for data retrieval
• Use dynamic finders methods
• Create named scopes to add custom finding behavior to your models
• Check for the existence of particular records
• Perform various calculations on Active Record models

Model.find(:all, options) is equivalent to Model.all(options)

# Very inefficient when users table has thousands of rows.

User.all.each do |user|

 NewsLetter.weekly_deliver(user)

end

> mysqldump -u username -ppassword database_name > FILE.sql

• Import A MySQL Database

> # mysql -u username -ppassword database_name < FILE.sql

Summary:In this tutorial, you will learn how to use database cursor in stored procedure to loop over a result set in MySQL.

MySQL supports cursor in stored procedures, functions and triggers. Cursor is used to iterate through a set of rows, which returned by a query, and process individual row. Currently with all versions greater 5.x, MySQL cursor has following properties:

• Read only: it means you cannot update the cursor.
• Non-scrollable: it only can traverse in one direction and cannot skip, move back or forth in result set.
• Asensitive: you should avoid update table while open a cursor on that table otherwise you may get unexpected results.

MySQL supports following statements for working with cursor.

First you have to declare a cursor using DECLARE statement:

DELIMITER $$
 DROP PROCEDURE IF EXISTS CursorProc$$
 CREATE PROCEDURE CursorProc()
 BEGIN
 DECLARE  no_more_products, quantity_in_stock INT DEFAULT 0;
 DECLARE  prd_code VARCHAR(255);
             DECLARE  cur_product CURSOR FOR
 SELECT  productCode FROM products;
   DECLARE  CONTINUE HANDLER FOR NOT FOUND
 SET  no_more_products = 1;

 /* for  loggging information */
 CREATE  TABLE infologs (
 Id int(11) NOT NULL AUTO_INCREMENT,
 Msg varchar(255) NOT NULL,
 PRIMARY KEY (Id)
 );
 OPEN  cur_product;

 FETCH  cur_product INTO prd_code;
 REPEAT
 SELECT  quantityInStock INTO quantity_in_stock
 FROM  products
 WHERE  productCode = prd_code;

 IF  quantity_in_stock < 100 THEN
 INSERT  INTO infologs(msg)
 VALUES  (prd_code);
 END  IF;
 FETCH  cur_product INTO prd_code;
 UNTIL  no_more_products = 1
 END REPEAT;
 CLOSE  cur_product;
 SELECT *  FROM infologs;
 DROP TABLE  infologs;
 END$$
 DELIMITER;

Summary: In this tutorial, you will learn how to use various loop statements including WHILE, REPEAT and LOOP to run a block of code repeatedly in MySQL.

MySQL stored programming language supports loop which allows you to process commands iteratively. The standard loops are discuss as follows

WHILE loop

The syntax of while loop is as follows:

DELIMITER $$
DROP PROCEDURE IF EXISTS WhileLoopProc$$
CREATE PROCEDURE WhileLoopProc()
      BEGIN
              DECLARE x  INT;
              DECLARE str  VARCHAR(255);
              SET x = 1;
              SET str =  '';
              WHILE x  <= 5 DO
                          SET  str = CONCAT(str,x,',');
                          SET  x = x + 1;
              END WHILE;
              SELECT str;
      END$$
  DELIMITER ;

DELIMITER $$
DROP PROCEDURE IF EXISTS RepeatLoopProc$$
CREATE PROCEDURE RepeatLoopProc()
      BEGIN
              DECLARE x  INT;
              DECLARE str  VARCHAR(255);
              SET x = 1;
              SET str =  '';
              REPEAT
                          SET  str = CONCAT(str,x,',');
                          SET  x = x + 1;
              UNTIL x  > 5
              END REPEAT;
              SELECT str;
      END$$
DELIMITER ;

DELIMITER $$
DROP PROCEDURE IF EXISTS LOOPLoopProc$$
CREATE PROCEDURE LOOPLoopProc()
      BEGIN
              DECLARE x  INT;
              DECLARE str  VARCHAR(255);
              SET x = 1;
              SET str =  '';
              loop_label:  LOOP
                          IF  x > 10 THEN
                                      LEAVE  loop_label;
                          END  IF;
                          SET  x = x + 1;
                          IF  (x mod 2) THEN
                                      ITERATE  loop_label;
                          ELSE
                                      SET  str = CONCAT(str,x,',');
                          END  IF;

              END LOOP;
              SELECT str;
      END$$
DELIMITER ;

Conditional control enables you to execute the code based on the value of an expression or a combination of expression using logical operators. MySQL supports two conditional control statement such as IF and CASE.

The IF Statement

The syntax of IF statement is simple as follows:

Summary: In this tutorial, you will learn how to write MySQL stored procedures with parameters. We will also give you a couple of stored procedure examples to help you understand more about using parameters in stored procedures.

Almost stored procedures you develop require parameters. Parameters make the stored procedure more flexible and useful. In MySQL, a parameter has one of three modes IN, OUT and INOUT.

• IN this is the default mode. IN indicates that a parameter can be passed into stored procedures but any modification inside stored procedure does not change parameter. Suppose you pass parameter Id, which is equal 10, into stored procedure GetAll(Id), after executing the stored procedure the value of Id is still 10 even though the GetAll stored procedure can change the value of it.
• OUT this mode indicates that stored procedure can change this parameter and pass back to the calling program.
• INOUT obviously this mode is combined of IN and OUT mode; you can pass parameter into stored procedure and get it back with the new value from calling program.

The syntax of defining a parameter in stored procedure is as follows:

MODE param_name param_type(param_size)

MODE could be IN, OUT or INOUT depending on the purpose of parameter you specified.
param_name is the name of the parameter. The name must not be the same as the column name of tables and following naming convention. Followed the parameter name is the type of parameter and its size.

Each parameter is separated by a comma if the stored procedure more than one parameter.

Let’s practice with following examples to understand more.

The first example is a stored procedure to get all offices in a country. Here is the SQL source code:

DELIMITER //
 CREATE PROCEDURE GetOfficeByCountry(IN countryName VARCHAR(255))
    BEGIN
		SELECT city, phone
		FROM offices
		WHERE country = countryName;
    END //
 DELIMITER ;

DELIMITER $$
CREATE PROCEDURE CountOrderByStatus(
		IN orderStatus VARCHAR(25),
		OUT total INT)
    BEGIN
		SELECT count(orderNumber)
		INTO total
		FROM orders
		WHERE status = orderStatus;
    END$$
 DELIMITER ;

DELIMITER $$
CREATE PROCEDURE `Capitalize`(INOUT str VARCHAR(1024))
BEGIN
	DECLARE i INT DEFAULT 1;
	DECLARE myc, pc CHAR(1);
 	DECLARE outstr VARCHAR(1000) DEFAULT str;
 	WHILE i <= CHAR_LENGTH(str) DO
		SET myc = SUBSTRING(str, i, 1);
		SET pc = CASE WHEN i = 1 THEN ' '
			      ELSE SUBSTRING(str, i - 1, 1)
			 END;
		IF pc IN (' ', '&', '''', '_', '?', ';', ':', '!', ',', '-', '/', '(', '.') THEN
		    SET outstr = INSERT(outstr, i, 1, UPPER(myc));
		END IF;
		SET i = i + 1;
	END WHILE;
	SET str = outstr;
END$$
DELIMITER ;