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SQL Interview Success: Unlocking the Top 5 Frequently Asked Queries

 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

5 Python File Modes You Need

Here're top five Python file modes explained. The purpose is to open, read, write the files. There are occasions you need to deal with data, which is present in the files. You need to give correct file-modes to handle the files in Python.

Python file modes crucial to handle the files. Here is the list of file modes to use correctly in your program.
Python file open modes

5 Python File Modes You Need

Here's an example code how to you can use file mode:

filename = input('Enter a filename : ')
f1 = open(filename, 'mode')

1- Python File mode w 

To open the file for writing, you need 'w' mode. The beauty of this is If the file does not exist, it creates one. This mode's purpose is to write the file. If you try to read, you will get an error.

2- Python File mode w+

To Open the file for Reading and Writing, you need 'w+' mode. For instance, you used w+, you have tried to read the file - after writing, it displays blank. The reason is after writing cursor position will point at the end of the file.

3- Python File mode a

It appends the records at the end of the existing file. The file must exist to use this mode.

4- Python File mode r

To open a file in read-only mode. If the file does not exist, it throws an error.

5- Python File mode r+

Both read and write. When you write the data to the file, it writes at the end. Now, the cursor is at the end of the file. When you perform read, it gives blank.

In the 'r+' mode, if the file does not exist, and if you try to read, which gives an error.

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