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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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How to Use Help Command in HDFS

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Sometimes as a Hadoop developer it is difficult to remember all the Hadoop commands. The HELP command useful to know the correct syntax.

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How to List all HDFS Commands

hadoop
hadoop fs   ==> Enter

This will list all Hadoop commands.

Help Command in HDFS

Hadoop commands are the flavor of UNIX. If you want to see each Command description, you can go for Hadoop help command. You can use the below command for help.

hadoop fs -hlep ls 

Deleting a File in Hadoop HDFS

The below command helps   how to delete a file from Hadop cluster.

hadoop fs -rm exmaple.txt

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