Default values – This is a value that will be entered automatically if the user doesn’t enter a value. For example, if they’re making an order and the number of item is not specified then probably you would use a default of one so that one item will be ordered.
Field – a field is one item in a record, in other words, for example one record in a customer database will be Mr. Jones and his address and telephone number and maybe date of birth, depeding..maybe not date of birth and one thing within that record for example a city will be one field.
Primary key – in a table there is a key, for example in a student database, the key might be the student’s ID or in a government database the key might be the person’s national insurance number and those are use these keys because they are different for every record. A primary key is the key a cannot have duplicate, so for a person or a national insurance number can only be use for one person and never duplicate.
Lock – A table or sometimes a record will be locked when its being updated. The reason for that if two people are trying to update record at the same time then whoever enters first the change will be made. But the second person to enter it will change it again. Now to stop causing problems when a record is open it is locked and then when they finish updating then it is unlocked again.
Many to many relationships – these are when two tables could be joined, for example, if the student is taking many subjects and the subject is being made it is being taken by many students then we can say that is many to many relationships. Another example will be a product could be available in many colors and a certain color could be available for many products so those are many to many relationships. And only have that in a database we have to put a table in between them to join them together.
One to many relationship – this is a way in an example… for example a person who only live in on city or for example, their mailing address will be one city. Whereas is a city could have many people.
One to one relationship – isn’t used so often. Is where for example, one person has one address. The tables are joined straight together and it doesn’t need to be used because that information could be kept in the same table but sometimes its use for security so that a separate table have more restrictions on it.
Record – a record is one line in a table. For example in a customer table, one person will have on record. In a subjects table, math will be one record, English will be in another record and this will have associated information. For example, in a customer table, one customer would be one record and that record will be include his name, address, telephone number, whole thing together is a record
Schema – a schema is a diagram showing how a whole of table is related together, for example, a customer is related to an order, an order is related to order item and order item is related to a product and if we carry on with that the whole thing together is a scheme
Table – a table is a collection of records that are very similar, so for example you have a customer table, or a subjects table, or an orders table and the orders table for example will contain order. Maybe the date and the customer and other information like that.
