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MySQL Interview
IFNULLIFNULL(expression, alt_value): The expression to test whether is NULL, alt_value: The value to return if expression is NULLUNIONSELECT City, Country FROM CustomersWHERE Country='Germany'UNION...…
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Sql
SELECTSELECT column1, column2, ... FROM table_name;SELECT * FROM table_name;SELECT DISTINCTstatement is used to return only distinct (different) values.SELECT DISTINCT column1, column2, ... FROM ta...…
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Git
git diff compare the file from two different branches: git diff <branch a name> <branch b name> <file path>: in terminal, the file shows up with differences, the marker “^M” mean...…
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System Engineering
System Engineering IntroductionWhat is system engineering design, test, and evaluation to meet cost, schedule and techinical performance understand customers needs (risk management etc) ...…
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Other Concepts
SkyHook Skyhook hybrids positioning technology, incorporates Wi-Fi, GPS, cell towers, IP address and device sensors, to identify device location precisely. As of 2020. Skyhook’s coverage area inc...…
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Java
JDK vs JRE vs JVM JDK – Java Development Kit (in short JDK) is Kit which provides the environment to develop and execute(run) the Java program. JDK is a kit(or package) which includes two thin...…
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React
Accessing a Global VariableThe window is the global object in the browser environment. Any property attached to the window object can be accessed from any script on the web page, including the scri...…
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System Design
Load-Balancing Goal: help developing a scalable app, allow distributing loads across servers based on metrics such as random, round-robin, random with weighting for memory or cpu utilization etc. ...…