feature: add example

Author: cyyeh

.gitignore

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+.DS_Store

README.md

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-# vulcan-sql-examples
+# VulcanSQL Examples
+
+This repo contains source code of VulcanSQL examples.

covid19-global-data-api/.gitignore

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+node_modules
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+.DS_Store

covid19-global-data-api/README.md

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+# COVID 19 Global Data API
+
+## Project Introduction
+
+This sample project is based on [VulcanSQL](https://github.com/Canner/vulcan-sql/). VulcanSQL is a Data API Framework that helps data folks build scalable data APIs using only SQL templates without any backend skills required.
+
+In this project, we expose some apis based on COVID 19 Global Data downloaded from [WHO Coronavirus (COVID-19) Dashboard](https://covid19.who.int/data), and `WHO-COVID-19-global-data.csv` is the downloaded file.
+
+## Setup
+
+- [Install VulcanSQL from NPM](https://vulcansql.com/docs/get-started/installation#install-from-npm)
+- `npm install` in the root of project directory
+- `vulcan start --watch` and `vulcan catalog` in two seperate shell windows, and you can now access API documentation at `http://localhost:3000/docs` and catalog at `http://localhost:4000`
+
+## APIs introduction
+
+- `/countries`: get a list of countries and their country codes
+- `/max_cases`: get a list of countries or WHO regions that have the most cases on a given date range
+- `/max_deaths`: get a list of countries or WHO regions that have the most deaths on a given date range
+- `/min_cases`: get a list of countries or WHO regions that have the minimum cases on a given date range
+- `/min_deaths`: get a list of countries or WHO regions that have the minimum deaths on a given date range
+- `/reports`: get a list of COVID-19 reports by countries and date range
+- `/who_regions`: get a list of WHO regions
+
+## Data introduction
+
+|Field name|Type|Description|
+|---|---|---|
+|Date_reported|Date|Date of reporting to WHO|
+|Country_code|String|ISO Alpha-2 country code|
+|Country|String|Country, territory, area|
+|WHO_region|String|WHO regional offices: WHO Member States are grouped into six WHO regions -- Regional Office for Africa (AFRO), Regional Office for the Americas (AMRO), Regional Office for South-East Asia (SEARO), Regional Office for Europe (EURO), Regional Office for the Eastern Mediterranean (EMRO), and Regional Office for the Western Pacific (WPRO).|
+|New_cases|Integer|New confirmed cases. Calculated by subtracting previous cumulative case count from current cumulative cases count.|
+|Cumulative_cases|Integer|Cumulative confirmed cases reported to WHO to date.|
+|New_deaths|Integer|New confirmed deaths. Calculated by subtracting previous cumulative deaths from current cumulative deaths.|
+|Cumulative_deaths|Integer|Cumulative confirmed deaths reported to WHO to date.|
+
+## Data Visualizations
+
+- [Streamlit](visualizations/streamlit/)