Tutorial by Examples: table

Frozenset's are immutable and not assignable

foo = frozenset(["bar", 1, "Hello!"]) foo[2] = 7 # ERROR foo.add(3) # ERROR Second line would return an error since frozenset members once created aren't assignable. Third line would return error as frozensets do not support functions that can manipulate members.

Python Language • Immutable datatypes(int, float, str, tuple and frozensets)

Update query with join between two tables alternative since Postresql does not support join in update query.

update <SCHEMA_NAME>.<TABLE_NAME_1> AS A SET <COLUMN_1> = True FROM <SCHEMA_NAME>.<TABLE_NAME_2> AS B WHERE A.<COLUMN_2> = B.<COLUMN_2> AND A.<COLUMN_3> = B.<COLUMN_3>

postgresql • Postgres Tip and Tricks

Query to Copy/Move/Transafer table data from one database to other database table with same schema

First Execute CREATE EXTENSION DBLINK; Then INSERT INTO <SCHEMA_NAME>.<TABLE_NAME_1> SELECT * FROM DBLINK( 'HOST=<IP-ADDRESS> USER=<USERNAME> PASSWORD=<PASSWORD> DBNAME=<DATABASE>', 'SELECT * FROM <SCHEMA_NAME>.<TABLE_NAME_2...

postgresql • Postgres Tip and Tricks

Set a custom prefix for WordPress tables

When you install WordPress to your server, the installation script will place a prefix in front of all the WordPress MySQL table names. This prefix is set to 'wp_' by default. The WordPress posts table will be called wp_posts for example. By changing the table prefix you can create some security by ...

WordPress • Secure your installation

chai-immutable plugin

Install from npm chai, chai-immutable, and ts-node npm install --save-dev chai chai-immutable ts-node Install types for mocha and chai npm install --save-dev @types/mocha @types/chai Write simple test file: import {List, Set} from 'immutable'; import * as chai from 'cha...

TypeScript • Unit Testing

Create Table in Java using Document API

In the following example we will be creating a table called Membership using the AWS Java SDK for DynamoDB. The table will consist of items that represent team assignments. The table will be partitioned by TeamID. Each team will have multiple members, identified by the MemberID (as a sort key). AWS...

amazon-dynamodb • How to create a DynamoDB Table

Table per hierarchy

This approach will generate one table on the database to represent all the inheritance structure. Example: public abstract class Person { public int Id { get; set; } public string Name { get; set; } public DateTime BirthDate { get; set; } } public class Employee : Person { ...

Entity Framework • Inheritance with EntityFramework (Code First)

Table per type

This approach will generate (n+1) tables on the database to represent all the inheritance structure where n is the number of subclasses. How to: public abstract class Person { public int Id { get; set; } public string Name { get; set; } public DateTime BirthDate { get; set; } } ...

Entity Framework • Inheritance with EntityFramework (Code First)

Create Immutable version of DateTime from Mutable prior PHP 5.6

To create \DateTimeImmutable in PHP 5.6+ use: \DateTimeImmutable::createFromMutable($concrete); Prior PHP 5.6 you can use: \DateTimeImmutable::createFromFormat(\DateTime::ISO8601, $mutable->format(\DateTime::ISO8601), $mutable->getTimezone());

PHP • Datetime Class

Updatable nested serializers

Nested serializers by default don't support create and update. To support this without duplicating DRF create/update logic, it is important to remove the nested data from validated_data before delegating to super: # an ordinary serializer class UserProfileSerializer(serializers.ModelSerializer): ...

django-rest-framework • Serializers

Create a table with columns to store sub-second time.

CREATE TABLE times ( dt DATETIME(3), ts TIMESTAMP(3) ); makes a table with millisecond-precision date / time fields. INSERT INTO times VALUES (NOW(3), NOW(3)); inserts a row containing NOW() values with millisecond precision into the table. INSERT INTO times VALUES ('2015-01...

MySQL • Time with subsecond precision

Drop tables from database

DROP TABLE Database.table_name

MySQL • Drop Table

Immutable collections

The System.Collections.Immutable NuGet package provides immutable collection classes. Creating and adding items var stack = ImmutableStack.Create<int>(); var stack2 = stack.Push(1); // stack is still empty, stack2 contains 1 var stack3 = stack.Push(2); // stack2 still contains only one, st...

C# Language • Functional Programming

Connect to Server, Create Table, Query Data

Install the package: $ pip install pymssql import pymssql SERVER = "servername" USER = "username" PASSWORD = "password" DATABASE = "dbname" connection = pymssql.connect(server=SERVER, user=USER, password=PASSWORD, database=DATABASE...

Python Language • Connecting Python to SQL Server

The Basics (Tables and Inline CSS)

Tables for Layout The structure of an HTML email file is similar to that of a web page: <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Hello!</title> </head> <body> &...

email • Getting started with email

Self Referencing Employee Table

ms-access • Self-Referencing tables

Creating a Hash Table

Example of creating an empty HashTable: $hashTable = @{} Example of creating a HashTable with data: $hashTable = @{ Name1 = 'Value' Name2 = 'Value' Name3 = 'Value3' }

PowerShell • HashTables

Access a hash table value by key.

An example of defining a hash table and accessing a value by the key $hashTable = @{ Key1 = 'Value1' Key2 = 'Value2' } $hashTable.Key1 #output Value1 An example of accessing a key with invalid characters for a property name: $hashTable = @{ 'Key 1' = 'Value3' Key2 = 'Val...

PowerShell • HashTables

Looping over a hash table

$hashTable = @{ Key1 = 'Value1' Key2 = 'Value2' } foreach($key in $hashTable.Keys) { $value = $hashTable.$key Write-Output "$key : $value" } #Output Key1 : Value1 Key2 : Value2

PowerShell • HashTables

Add a key value pair to an existing hash table

An example, to add a "Key2" key with a value of "Value2" to the hash table, using the addition operator: $hashTable = @{ Key1 = 'Value1' } $hashTable += @{Key2 = 'Value2'} $hashTable #Output Name Value ---- -----...

PowerShell • HashTables