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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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Python Program: JSON to CSV Conversion

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JavaScript object notion is also called JSON file, it's data you can write to a CSV file. Here's a sample python logic for your ready reference. 




You can write a simple python program by importing the JSON, and CSV packages. This is your first step. It is helpful to use all the JSON methods in your python logic. That means the required package is JSON.

So far, so good. In the next step, I'll show you how to write a Python program. You'll also find each term explained.


What is JSON File

JSON is key value pair file. The popular use of JSON file is to transmit data between heterogeneous applications. Python supports JSON file.


What is CSV File

The CSV is comma separated file. It is popularly used to send and receive data.


How to Write JSON file data to a CSV file

Here the JSON data that has written to CSV file. It's simple method and you can use for CSV file conversion use.

import csv, json

json_string = '[{"value1": 1, "value2": 2,"value3": 1.234}]'
data = json.loads(json_string)
headers = data[0].keys()

with open('sample.csv', 'w') as f:
writer = csv.DictWriter(f, fieldnames=headers)
writer.writeheader()
writer.writerows(data)


with open('sample.csv', 'r') as f:
    print(f)
    for row in f:
        print(row)

Output:

<_io.TextIOWrapper name='file.csv' mode='r' encoding='UTF-8'>
value1,value2,value3

1,2,1.234


** Process exited - Return Code: 0 **
Press Enter to exit terminal

Conclusion

The output CSV file has both headers and rows, and the data is comma seprated.


References

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