January 2002
Intermediate to advanced
640 pages
16h 39m
English
Content preview from Practical PostgreSQLBecome 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,
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Chapter 5. Operators and Functions
This chapter expands on the operators and functions available to PostgreSQL. These character symbols and identifiers allow you to flexibly modify and compare results within SQL statements. The results of these operations can be used in a variety of ways, from updating existing row data, to constraining query results to only rows matching particular conditions.
PostgreSQL supports the usual variety of standard SQL operators and functions as defined by
the ANSI/ISO SQL standards, such as mathematical operators, basic text formatting functions, and
date and time value extraction. PostgreSQL also comes with a rich set of custom PostgreSQL
extensions, such as regular expression comparison operators, and the flexible to_char(
) text conversion function.
Take note that these sections describe the native operators and functions available to PostgreSQL. An excellent feature of PostgreSQL is its extensibility in this area. Once you have a solid understanding of operators and functions, you may be interested in developing your own. These techniques are described in Chapter 7.
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