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09 Dec 09

Accessing a MySQL database from Node.JS « Devthought

connection.query("SELECT * FROM TABLE").addCallback(function(result){
for (var i = 0, l = result.ROWS.length; i < l; i++){
var row = result.ROWS[i];
// do something with the data
}
});

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mysql access javascript slayer node.js

15 Sep 09

MySQL :: An Introduction to Database Normalization

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mysql database normalization tutorial codd

The first normal form (or 1NF) requires that the values in each column of a table are atomic. By atomic we mean that there are no sets of values within a column
One method for bringing a table into first normal form is to separate the entities contained in the table into separate tables
12 more annotations...
- surrogate primary key -- an artificial primary key used when a natural primary key is either unavailable or impractical.
- when using a surrogate primary key it is still important to create a UNIQUE key to ensure that duplicate records are not created inadvertently (but some would argue that if you need a UNIQUE key it would be better to stick to a composite primary key).
- There are various types of relationships that can exist between two tables:
  
  One to (Zero or) One
  One to (Zero or) Many
  Many to Many
- To represent a many-to-many relationship in a relational database we need a third table to serve as a link between the two.
- When we have a one-to-many relationship, we place a foreign key in the table representing the �many�, pointing to the primary key of the table representing the �one�.
- Columns in a table that refer to primary keys from another table are known as foreign keys, and serve the purpose of defining data relationships.
- the Second Normal Form (or 2NF) deals with relationships between composite key columns and non-key columns.
- The second normal form (or 2NF) any non-key columns must depend on the entire primary key. In the case of a composite primary key, this means that a non-key column cannot depend on only part of the composite key.
- To bring the Review table into compliance with 2NF, the Author_URL must be moved to the Author table.
- Third Normal Form (3NF) requires that all columns depend directly on the primary key. Tables violate the Third Normal Form when one column depends on another column, which in turn depends on the primary key (a transitive dependency).
- In the Publisher table the City and State fields are really dependent on the Zip column and not the Publisher_ID. To bring this table into compliance with Third Normal Form, we would need a table based on zip code:
- With our tables now separated by entity, we join the tables together in our SELECT queries and other statements to retrieve and manipulate related data

10 Sep 09

How FriendFeed uses MySQL to store schema-less data - Bret Taylor's blog

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mysql database performance scalability architecture nosql

making schema changes or adding indexes to a database with more than 10 - 20 million rows completely locks the database for hours at a time. Removing old indexes takes just as much time, and not removing them hurts performance because the database will continue to read and write to those unused blocks on every INSERT, pushing important blocks out of memory
We can change the "schema" simply by storing new properties.
3 more annotations...
- We index data in these entities by storing indexes in separate MySQL tables. If we want to index three properties in each entity, we will have three MySQL tables - one for each index.
- We can store new properties and index them in a day's time rather than a week's time, and we don't need to swap MySQL masters and slaves or do any other scary operational work to make it happen.
- Since our database is sharded, and indexes for an entity can be stored on different shards than the entities themselves, consistency is an issue

17 Jun 09

Optimizing MySQL: Configuration Directives

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mysql configuration optimization

03 Jun 09

SQL functions programmer's reference - Búsqueda de libros de Google

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sql mysql db2 oracle programming function reference

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