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Constraints

NOT NULL CONSTRAINT -    Ensures that a column cannot have a null value. DEFAULT CONSTRAINT -    Provides a default value for a column when none is specified  UNIQUE CONSTRAINT -   Ensures that all values in columns are different  CHECK CONSTRAINT -   Makes sure that all values in a column satisfy certain criteria  PRIMARY KEY CONSTRAINT -   Used to uniquely identify a row in the table  FOREIGN KEY CONSTRAINT -   Used to ensure referential integrity of the data  Primary Key - is used uniquely to identify each row in a table . It can consist of one or more columns on a table . When Multiple columns are used on a table it is called composite key.  Foreign Key - Foreign key is a column or columns that references a column most often primary key of another table . The purpose of foreign key is to maintain referential integrity of the data. Pg admin  Data base - training - right click on training - query click  Always add semi colen to run the query  Int - integer  varchar - variable charact
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Transportation Part 2

 #Principles in Transportation 

1. Economies of Scale - There are certain FC And VC , FC remains same but VC changes . Fc divided into many units when the units are more . You are selling at lower cost. A single product may not have single demand therefore they try to combine them . More quantity you are transporting more cost is divided .

2. Economies of distance ( tapering principle ) - Assume you are transferring a parcel 500 km from the point , and another to 500 km , Then in that case If you are covering 1000 km at stretch so that your cost is reducing .

Assume 2 parcel to send to place a and b both are 500 km from Mumbai , one is in Northern and other is southern , But compare this with 1000 km straight gone . 1000km taken at stretch is less costly , it is because you were spending a lot of amount in loading and unloading when it is not stretched . 

#Participants - 

1. Shipper 

2. Receiver 

3. Carrier 

4. Government 

5. Public 

#Factors Influencing Transportation 

  • Nature of goods 
  • Availability 
  • Distance 
  • Cost 
  • Delivery time 
  • Frequency 
  • Capabilities of mode 
  • Speed 
  • Reliability 
  • Safety 

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