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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

How to Decode TLV Quickly

TLV format contains three parts Tag, Length, and value. In a credit card or financial transactions, the TLV protocol supports this format. Below, you will find the ideas to decode TLV data quickly. 

According to IBM, the tag tells what type of data it is. The length field denotes the length of the value. The value-field denotes the actual value.

Structure of TLV.

TLV comprises three field values.

  1. Tag
  2. Length
  3. Value

How to Decode TLV

Decoding of TLV

The EMV labs developed tags which in turn part of EMV protocol. Each tag has an unique meaning. And the Tag and Length together takes 1 to 4 bytes of memory.

1. The Best example for TLV.

Below is the way to decode the EMV tag. The first part of the TLV format is TAG. The second part is LENGTH, and finally the VALUE.

Syntax of EMV tag:

[Tag][Value Length][Value] (ex. "9F4005F000F0A001")


Tag Name = 9F40

Value Length (in bytes) = 05 

Value (Hex representation of bytes. Example, "F0" – 1-byte) = F000F0A001

Finally, what is 9F40 tag? The EMV company assigns a value to it. Check out the complete list of EMV Tags and meanings.

2. How to read the TLV

Let me elaborate on the memory the EMV tag takes. The breakup of memory allocation is as below.


Tag: 1 or 2 bytes.

Length: 05

Value length:

F0-00-F0-A0-01 ==> 5 Bytes

The F0 is the HEX value of length 1. So the total length of the value altogether is 5 bytes.

F0+00+F0+A0+01= Total 5 bytes



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