January 2002
Intermediate to advanced
640 pages
16h 39m
English
Content preview from Practical PostgreSQL
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Tables in PostgreSQL
If you are already familiar with SQL or other RDBMS packages, you probably already have a solid understanding of many of the relational database concepts put forth in this chapter. However, each RDBMS handles tables differently at the system level. This section takes a closer look at tables as they are implemented in PostgreSQL.
System Columns
PostgreSQL defines a series of system columns in all tables, which are normally invisible to the user (e.g., they will not be shown by queries unless explicitly requested). These columns contain meta-data about the content of the table’s rows. Many of these contain data that can help to differentiate between tuples (an individual state of a row) when working with transaction blocks. (See Chapter 7 for more about transactions.)
As a result of these system-defined columns, in addition to the user-defined columns of a table, any inserted row will have values in each of the columns described in Table 3-25.
Table 3-25. System columns
|
Column |
Description |
|---|---|
|
|
The unique object identifier of a row. PostgreSQL automatically adds this 4-byte number to all rows. It is never re-used within the same table. |
|
|
The oid of the table that contains a row. The name and oid of a table are related by
the |
|
|
The transaction identifier of the inserting transaction of a tuple. |
|
|
The command identifier, starting at 0, associated ... |
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.