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9 Aug 2016
Jeffrey J. Keller
Window Functions: Part Two: Aggregating Data
In part one of this series on SQL Server window functions, the functionality of the OVER() clause was discussed. This article will focus on aggregate functions. The majority of these can be used in conjunction with OVER. Some, like SUM() and AVG(), are widely used. Others — including VARP() and CHECKSUM_AGG() — are not as well-known, but are potentially quite useful. OVER defines the user-specified range on which a function is applied.
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2 Aug 2016
Patrycja Dybka
The History of Slonik, the PostgreSQL Elephant Logo
Logos are powerful. What better way to remind people of a product than an eye-catching, memorable symbol? With that in mind, today we’ll answer the question ‘Why did PostgreSQL choose an elephant for its logo?’ Every product or company has its logo – something that identifies and encapsulates the essence of their brand. In time, it practically becomes the brand: can you imagine McDonald’s without its golden arches? What if the Coca-Cola logo was suddenly done in purple block print?
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23 Jun 2016
Maria Alcaraz
Your First Steps With the Geography Data Type
Geographical applications are everywhere: GPS and sat nav systems, maps, get-a-taxi apps, real estate portals, etc. Behind each of them is a spatial database storing geographical data, and supporting spatial queries. In this article, we will introduce PostGIS, the main open-source spatial database manager. PostGIS is a spatial database extension for the PostgreSQL relational database. It adds support for geographic objects, allowing location queries to be run in SQL. PostGIS adds two main data types to PostgreSQL: geography and geometry.
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21 Jun 2016
Jeffrey J. Keller
Window Functions in SQL Server: Part One: The OVER() Clause
Window functions were first introduced in standard SQL 2003 and then extended in SQL 2008. Since SQL Server 2005, Microsoft has been steadily improving window functions in the database engine. These functions perform an aggregate operation against a user-defined range of rows (the window) and return a detail-level value for each row. Well-known aggregate functions include SUM, AVG, MIN, MAX, and many others. Recent versions of SQL Server have introduced ranking and analytic functions such as LAG, LEAD, RANK, CUME_DIST, and many others.
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19 May 2016
Maria Alcaraz
Pivot Tables in PostgreSQL Using the Crosstab Function
Some years ago, when PostgreSQL version 8.3 was released, a new extension called tablefunc was introduced. This extension provides a really interesting set of functions. One of them is the crosstab function, which is used for pivot table creation. That's what we'll cover in this article. The simplest way to explain how this function works is using an example with a pivot table. First, we will explain our initial point from a practical perspective, then we'll define the pivot table we want.
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5 May 2015
Adrian Więch
5 Tips to Optimize Your SQL Queries
The SQL Language seems easy to learn – the commands follow a simple syntax and don't describe the specific algorithms used to retrieve data. The simplicity might, however, be deceptive. Not all the database functions operate with the same efficiency. Two very similar queries can vary significantly in terms of the computation time. This article presents some of the best practices that can greatly boost your SQL queries. 1. Learn How to Create Indexes Properly Learning how to index properly is the best thing you can do to improve the performance of your SQL queries.
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14 Jan 2015
Patrycja Dybka
Oracle Collations: Binary and Linguistic Collations
Oracle bases its language support on the values of parameters that begin with NLS. These parameters specify, for example, how to display currency or how the name of a day is spelled. The table below presents some of the NLS parameters. By using one of them, NLS_SORT, we can specify the sort method (binary or linguistic) for both SQL WHERE clause operations and NLSSORT function operations. Option Name Description NLS_LANG The current language, territory, and database character set, which are determined by session-wide globalization parameters.
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5 Jan 2015
Patrycja Dybka
PostgreSQL Collations
List Collations Collations in PostgreSQL are available depending on operating system support. For example, in Ubuntu type the following to list the names of the available collations: locale -a The same locales are available in PostgreSQL in the pg_collation catalog (mappings from an SQL name to operating system locale categories). select * from pg_collation; collname | collnamespace | collowner | collencoding | collcollate | collctype -----------+---------------+-----------+--------------+-------------+------------ default | 11 | 10 | -1 | | C | 11 | 10 | -1 | C | C POSIX | 11 | 10 | -1 | POSIX | POSIX C.
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31 Dec 2014
Agnieszka Kozubek-Krycuń
MySQL Collations
List Collations To list all collations available in MySQL, use SHOW COLLATION; +-------------------+----------+-----+---------+----------+---------+ | Collation | Charset | Id | Default | Compiled | Sortlen | +-------------------+----------+-----+---------+----------+---------+ | big5_chinese_ci | big5 | 1 | Yes | Yes | 1 | | big5_bin | big5 | 84 | | Yes | 1 | | dec8_swedish_ci | dec8 | 3 | Yes | Yes | 1 | | dec8_bin | dec8 | 69 | | Yes | 1 | | cp850_general_ci | cp850 | 4 | Yes | Yes | 1 | | cp850_bin | cp850 | 80 | | Yes | 1 | | hp8_english_ci | hp8 | 6 | Yes | Yes | 1 | | hp8_bin | hp8 | 72 | | Yes | 1 | | koi8r_general_ci | koi8r | 7 | Yes | Yes | 1 | | koi8r_bin | koi8r | 74 | | Yes | 1 | | latin1_german1_ci | latin1 | 5 | | Yes | 1 | | latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 | | latin1_danish_ci | latin1 | 15 | | Yes | 1 | | latin1_german2_ci | latin1 | 31 | | Yes | 2 | | latin1_bin | latin1 | 47 | | Yes | 1 | | latin1_general_ci | latin1 | 48 | | Yes | 1 | .
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22 Dec 2014
Agnieszka Kozubek-Krycuń
How Does a Database Sort Strings?
Different languages have different alphabets and different ways to order letters within those alphabets. For example, a Polish character Ł comes right after L and before M. In Swedish, a letter Å comes almost at the end, right after Z. In French diacritics marks have no impact on the alphabetical order, so the letters À, Á and  are treated as the letter A when sorting strings. A collation is a set of rules that defines how to compare and sort character strings.
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