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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 Find Folder Space in Linux Easily

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Here's an example that shows how to use find command to get directory utilized space in Linux. Many of a time during production support, or when crontab jobs failed, the reasons behind is space shortage of a directory.

Folder space


The find is handy you can use to get utilized space of a directory. That helps you to delete unnecessary files (that actually make some space).


Linux find command


Here's the find command that I have used in our project. You will find here the detailed explanation of this command and how to use it.


find /home/srini -xdev -ls | sort +6rn | head -20


Part#1: Directory path


In the first part,  after the find you need to give the directory's path for which folder you are going to find space.


Part#2: Option -xdev


The second part is -xdev, which gives the space usage of all the subdirectories.


Part#3: Option -ls


The next part is the -ls option that provides a sorted list of all the subdirectories. 

Part#4: Sort command


Then, the sort command sorts based on the value +6rn.


Sort options


-n Sort numerically (10 will sort after 2), ignore blanks and tabs 
-r Reverse the order of sort 
-f Sort upper- and lowercase together 
+x Ignore first x fields when sorting


Part#5: Option +xrn


The value +6 states to ignore 6 columns in the sort. The option +rn sorts in descending order of memory.


Sort command


Part#6: Option head -20


The head -20 gets the top 20 rows of directories details.

The command you can use to find the folders which takes more space.

Tip#1 I have gone through the best books and Udemy courses. I am giving here for your reference. Here is the book on Bash scripting and Udemy course is Bash Mastery helpful to know more.

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