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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

Data analysis report these are example queries to use on final data

Data analysis
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The role of data analysis will come into picture, once you have cleaned and filter the raw unstructured data. The next stage is called analysis. Your success of data analysis project is based preparing highly informative final report.

Tip: 
What could you investigate with data

To prepare analysis report, you need to ask some intelligent questions. These are example questions you can use. Based on your questions, you  need to prepare SQL queries to get the desired report or dashboard from your final data or cleaned data. 

The report or dashboard should be such that it should improve client business.
Let us use some case study on world bank data, what are the questions come into mind:

  1.  How much (in USD) is spent on healthcare in total in each country? 
  2. How much (in USD) is spent per capita in each country?
  3.  In which country is the most spent per person?
  4.  In which country is the least spent? 
  5. What is the average for each continent?
  6. For the world?
  7. What is the relationship between public and private health expenditure in each country? 
  8. Where do citizens spend more (private expenditure)? 
  9. Where does the state spend more (public expenditure)?
  10.  Is there a relationship between expenditure on healthcare and average life expectancy? 
  11. Does it make any difference if the expenditure is public or private?  
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