Question of the month February 2018 – Find query that gives different result

In SQL Server server, consider the following queries

query 1 : select 12a4;
query 2 : select 12e4;
query 3 : select 12f4;
query 4 : select 12g4;

Only one query will produce different result than others. Find the odd one out


Question of the month January 2018 – What is the practical usage of table with only one identity column?

I wonder why it is possible to create a table with only one column that too with identity property.

Have you ever used such a table?
What is the practical usage of table with just only one column with identity property?

Create table testing
test_id int identity(1,1) not null

Happy holidays from T-SQL

Curious to know the result of the following query? All you need to do is, in SQL Server, goto SSMS, set the result mode to Text (Press CTRL+T) and then execute the following code

set nocount on select space(17-len(replicate(
char(135),no)))+ replicate(char(135),no*2-1)
from (select top 10 row_number() over (
order by (select 1)) as no from 
(select 0 as no union all select 0 union 
all select 0) as t1 
cross join (select 0 as no union 
all select 0 union all 
select 0) as t2) as t union all 
select space(14)+replicate(char(124),5) union 
all select space(10)+
as varchar(100))

MySQL – Functions to get current date and time

You may often need to do some data filters based on the current date and time. In MySQL you can use the system functions available to get current date and time.

Refer the following examples.

1 Get current date



SELECT CURDATE() AS today_date

The result is


2 Get current time



SELECT CURTIME() AS today_time

The result is


3 Get Current Date and time

SELECT NOW() AS today_date_time

The result is


MySQL – How to create random number with fixed length?

One of my friends asked me “How do I create a 10 digit random number?”

MySQL supports RAND() system function which can produce a random number between 0 and 1 with 16 digits as the decimal part.

An example for a random value can be obtained using

SELECT RAND() as random_number;

The result is


Note that every time you run this code, you will get a different number.

Now to get 10 digit whole number, multiple it by 10000000000 and omit the decimal part by converting the result into UNSIGNED number

SELECT CAST(rand()*10000000000 as UNSIGNED) as random_number

The result is


This can be modified easily to get other number with fixed digits. For example if you want a random 4 digit number, you can use

SELECT CAST(rand()*10000 as UNSIGNED) as random_number

The result is


You can parameterize this to work for any number of fixed digits you want

MySQL – Simple ways to know version number with @@version and version()

If you want to know the version number of MySQL server, there are two simple methods available.

You can use system variable @@VERSION as shown below

SELECT @@VERSION as mysql_version;

Other method is to use system function VERSION()

SELECT VERSION() as mysql_version

Both of them returns the following result


Depends on the version of the server, you may get the different version number

Note : @@VERSION is already available in SQL Server database engine as a global variable to get the version information

MySQL – Concatenate column values for each group with GROUP_CONCAT function

As I said in my earlier posts, MySQL has some interesting features that make the things simpler. GROUP_CONCAT is one of such functions

This function concatenates values from several rows into a single row separated by the delimiter specified.

For example consider the following example with simple data set

create table customer_visits(customer_id int, place_name varchar(100));

insert into customer_visits (customer_id,place_name)
select 1,'Chennai' union all
select 1,'Denmark' union all
select 1,'USA' union all
select 2,'UK' union all
select 2,'Argentina'

Now for each customer id, if you want to concatenate the visited places in a single string separated by comma, you can use the following code

select customer_id,
       GROUP_CONCAT(place_name) as visited_places
group by

The result is

customer_id      visited_places
1                Chennai,Denmark,USA
2                UK,Argentina

Note that by default values are concatenated using comma. If you want to use different delimiter, say for example a semicolon (;), you can use SEPARATOR clause to do it as shown below.

select customer_id,
       GROUP_CONCAT(place_name SEPARATOR ';') as visited_places
group by

The result is

customer_id      visited_places
1                Chennai;Denmark;USA
2                UK;Argentina

GROUP_CONCAT is really a quite handy function.