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Published byFelicia Hoover Modified over 9 years ago
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RDBMS MySQL
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MySQL is a Relational Database Management System MySQL allows multiple tables to be related to each other. Similar to a Grandparent to a parent, a parent to child and so forth.
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Table Fields When you create a table make the first field an int, unsigned, auto increment and primary key – Ints are whole numbers – Unsigned are numbers that are positive only – Auto increment set the table to automatically add a new number in this field every time a new record is added to the next available number – Primary key means that the field is easily searched on and each record has a unique value.
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Table Fields for Child Tables If you have a child table the second field should be a foreign key – Foreign key field names are based on the table name and the field name manufactuer_id – The field type should be the same as the primary key of the parent table – Index this field – Other fields should then follow.
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Basic Flat table A flat table with manufacturer, product and comments. Basic until you start adding more data
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Basic Flat table More data Issues with duplicate info Table data sizes increases
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Basic Flat table Data may not be the same or inconsistent
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Normalization The solution of not having a flat table with duplicate data and inconsistent information is to normalize the tables. That is to make multiple tables from the one where data is not duplicated.
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Normalization Besides making the different tables you need to add the foreign keys Foreign key is a term for a field that is indexed and the values relate to another table.
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Normalization Besides making the different tables you need to add the foreign keys Foreign key is a term for a field that is indexed and the values relate to another table.
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The SQL call to retrieve this data is called a JOIN The type of JOIN we will be doing is a straight join using a WHERE clause The names of field now need to be proceeded with the table name. The table name and field is separated with a period. SELECT manufacture.name, product.name FROM manufacturer, product WHERE manufacturer.id = product.manufacturer_id
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The SQL call to retrieve this data is called a JOIN Additional parts of the WHERE statement can be added as well as ORDER Bys and GROUP BYs
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