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SQL Interview Success: Unlocking the Top 5 Frequently Asked Queries

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 Here are the five top commonly asked SQL queries in the interviews. These you can expect in Data Analyst, or, Data Engineer interviews. Top SQL Queries for Interviews 01. Joins The commonly asked question pertains to providing two tables, determining the number of rows that will return on various join types, and the resultant. Table1 -------- id ---- 1 1 2 3 Table2 -------- id ---- 1 3 1 NULL Output ------- Inner join --------------- 5 rows will return The result will be: =============== 1  1 1   1 1   1 1    1 3    3 02. Substring and Concat Here, we need to write an SQL query to make the upper case of the first letter and the small case of the remaining letter. Table1 ------ ename ===== raJu venKat kRIshna Solution: ========== SELECT CONCAT(UPPER(SUBSTRING(name, 1, 1)), LOWER(SUBSTRING(name, 2))) AS capitalized_name FROM Table1; 03. Case statement SQL Query ========= SELECT Code1, Code2,      CASE         WHEN Code1 = 'A' AND Code2 = 'AA' THEN "A" | "A
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Internet of Things Top Communication Protocols

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The IoT envisions hundreds or thousands of end-devices with sensing, actuating, processing, and communication capabilities able to be connected to the Internet. These devices can be directly connected using cellular technologies such as 2G/3G/Long Term Evolution and beyond (5G) or they can be connected through a gateway, forming a local area network, to get connection to the Internet.

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The latter is the case where the end-devices usually form Machine to Machine (M2M) networks using various radio technologies, such as Zigbee (based on the IEEE 802.15.4 Standard), Wi-Fi (based on
the IEEE 802.11 Standard), 6LowPAN over Zigbee (IPv6 over Low Power Personal Area Regardless the specific wireless technology used to deploy the M2M network, all the end-devices should make their data available to the Internet. 

This can be achieved either by sending the information to a proprietary web server accessible from the Internet or by employing the cloud.

#The role of protocols in IoT
#The role of protocols in IoT

Online platforms such as ThingSpeak.com or Open.Sen.se, among any other alternatives, are virtual clouds able to receive, store, and process data. Besides acting as remote data bases, M2M clouds also offer the following key services:

1. They offer Application Programming Interfaces (API) with built-in functions for end-users, thus providing the option to monitor and control end-devices remotely from a client device.

2. They act as asynchronous intermediate nodes between the end-devices and final applications running on devices such as smart phones, tablets or desktops. Our paper focuses on the protocols that handle the communication between the gateways, the public Internet, and the final applications (Figure 1). They are application layer protocols that are used to update online servers with the latest end-device values but also to carry commands from applications to the end-device actuators.

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