April 2002
Intermediate to advanced
336 pages
9h 58m
English
Content preview from Mastering Oracle SQLBecome 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.
Getting Dates In and Out of a Database
In the real world, dates are not always represented using Oracle’s DATE datatype. At various times, we’ll need to convert DATEs to other datatypes and vice versa. This is particularly true when we interface an Oracle database with an external system, for example when we are accepting date input from an external system in which dates are represented as strings of characters (or even as numbers), or when we are sending output from an Oracle database to another application that doesn’t understand Oracle’s DATE datatype. We also need to convert DATE values to text when we display dates on a screen or generate a printed report.
Oracle provides two extremely useful functions to convert dates:
TO_DATE
TO_CHAR
As their names suggest, TO_DATE is used to convert character data, or numeric data, into a DATE value, and TO_CHAR is used to convert a DATE value into a string of characters. Date formats, discussed later in this section, come in particularly handy for such conversions.
TO_DATE
TO_DATE is a built-in SQL function that converts a character string into a date. Input to the TO_DATE function can be a string literal, a PL/SQL variable, or a database column of the CHAR or VARCHAR2 datatype.
Call TO_DATE as follows:
TO_DATE(string [,format])
The syntax elements are:
- string
Specifies a string literal, a PL/SQL variable, or a database column containing character data (or even numeric data) convertible to a date.
- format
Specifies the format of the input string. ...
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.