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Software engineering facts, information, and skills categorized as PostgreSQL

Difference between null=True, blank=True in django

Priya Philip 1 year, 4 months ago

The main differnce for null and blank is 

Search database with regular expression in Django

Varghese Chacko 1 year, 5 months ago

Regex and iregex are  the two field lookups that enable us to search database with regular expressions. regex is case-sensitive where as iregexis case-insensitive.

Django - check for null in database

Varghese Chacko 1 year, 5 months ago

isnull

In django, the NULL valuein the database field is tested with field lookup isnull It takes either True or False, which correspond to SQL queries of IS NULL and IS NOT NULL, respectively.

Django field lookup - contains and icontains

Varghese Chacko 1 year, 5 months ago

Field lookups are how we specify the conditions in the WHERE clause of an SQL. They are specified as keyword arguments for QuerySet methodslike filter(), exclude() and get().

Django field lookup - exact and iexact

Varghese Chacko 1 year, 5 months ago

Field lookups are how we specify the conditions in the WHERE clause of an SQL. They are specified as keyword arguments for QuerySet methodslikefilter(), exclude() and get().

Export results of SQLs from Heroku using Data Clips

Varghese Chacko 1 year, 6 months ago

Heroku comes with nice database backup tools, both commandline and web based. But how to export results of an SQL query?

Concatenate two columns in results of SQL query in PostgreSQL

Varghese Chacko 1 year, 6 months ago

Very often, you will have the requirement to concatenate two columns in a table, on the fly in SELECT SQL. For example, first name and last name needed to be combined at username. The + operator is available in MicroSoft's database servers, but it is not part of PostgreSQL or SQL standard. PostgreSQL very well support string concatenation in SQL results. Let us assume that we have a table like

PG::Error (FATAL: too many connections for role "xxxxxxx")

Varghese Chacko 1 year, 6 months ago

PostgreSQL could be configured to limit number of simultaneous connections to the database. The heroku comes with plans having connection limits. The 'Hopby' plans comes with 20 connections where as standard plans comes startings with 120 conection. When we start developing and testing, especially automated testings, the hobby plans raise error PG::Error (FATAL: too many connections for role "xxxxxxx"). If we check the connections with heroku cli, we get

Top 10 Programming Languages Used in Web Development

Priya Philip 1 year, 6 months ago

Python
    Python is an interpreted(processed at runtime by the interpreter), object-oriented(supports Object-Oriented style), interactive, simple, easy to learn, portable, extensible, embeddable, high-level programming language for general-purpose programming. Created by Guido van Rossum at the National Research Institute for Mathematics and Computer Science in the Netherlands and first released in 1991. Python is derived from ABC, Modula-3, SmallTalk, Algol-68, C, C++, Unix shell and other scripting languages.Python's source code is avaliable under the GNU General Public License (GPL) which guarantees end users the freedom to run, study, share and modify the software.

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