CHAPTER 28 From Databases to (Photography web hosting)
CHAPTER 28 From Databases to Datatypes Taking time to properly design your project s data model is key to its success. Neglecting to do so can have dire consequences not only on storage requirements, but also on application performance, maintainability, and data integrity. In this chapter, you ll become better acquainted with the many facets of the hierarchy of objects within PostgreSQL. By its conclusion, you will be familiar with the following topics: The difference between the various levels of the PostgreSQL hierarchy, including clusters, databases, schemas, and tables. The purpose and range of PostgreSQL s supported datatypes. To facilitate reference, these datatypes are broken into four categories: date and time, numeric, textual, and Boolean. PostgreSQL s table attributes, which serve to further modify the behavior of tables and their columns. How to use advanced concepts, such as constraints and domains, to help further enforce data integrity. Working with Databases While most people think of a database as a single entity, the truth is that a single installation of PostgreSQL can handle many unique databases at the same time. This collection of databases is technically referred to as a cluster. In this section, we look at how to manipulate databases within a cluster. Default Databases By default, a PostgreSQL cluster comes with two template databases, template0 and template1. These databases contain all of the basic information that is needed to create new databases on the system. When you initially connect to a new installation of PostgreSQL, you ll want to connect to the template1 database and use that to create a new database. If there are schema objects or extensions that you need to load into PostgreSQL that you want all future databases to have access to, you can load them into the template1 database. The template0 database is mainly provided as a backup in case you manage to modify your template1 database in a manner that cannot be corrected.
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