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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

Big Data: Top Hadoop Interview Questions (4 of 5)

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1) What is MAP Reduce program? - You need to give actual steps in this program - You have to write scripts and codes 2) What is MAPReduce? -Mapreduce is a data processing model -It is combination of 2 parts. One is Mappers and the other one is Reducers 3)What will happen in Mapping phase? It takes the input data, and feeds each data element into the mapper 4)What is the function of Reducer? The reducer process all outputs from mapper and arrives at a final result 5)What kind of input required for Mapreduce? It should be structured in the form of (Key,Value) pairs 6)What is HDFS? HDFS is a file system designed for large-scale data processing under frameworks such as MapReduce. 7) Is HDFS like UNIX? No, but commands in HDFS works similarly to UNIX 8) What is Simple file command? hadoop fs -ls 9) How to copy data into HDFS file system? Copy a file into HDFS from local system 10) What is default working directory in HDFS? /user/$USER $USER ==> Your log