I have already written a similar article to delete duplicate records in SQL Server and MySQL.
Here, You can also access that articles.

Delete all duplicate rows in MySQL

Delete all duplicates rows except one in SQL Server

Recently, I got one request for one script to delete duplicate records in PostgreSQL.
Most of the Database Developers have such a requirement to delete duplicate records from the Database.

Like SQL Server, ROW_NUMBER() PARTITION BY is also available in PostgreSQL.
I have prepared this script, using simple inner query with the use of ROW_NUMBER() PARTITION BY clause.

Create a sample table:

CREATE TABLE tbl_RemoveDuplicate
(	
	ID INTEGER PRIMARY KEY
	,Name VARCHAR(150)
);

Insert few duplicate records:

INSERT INTO tbl_RemoveDuplicate VALUES
(1,'ABC'),(2,'XYZ')
,(3,'XYZ'),(4,'RFQ')
,(5,'PQR'),(6,'EFG')
,(7,'EFG'),(8,'ABC');

Except one, Delete all duplicate records:

DELETE FROM tbl_RemoveDuplicate
WHERE ID IN 
(SELECT ID
FROM (SELECT id,
	     ROW_NUMBER() OVER (partition BY Name ORDER BY ID) AS RowNumber
     FROM tbl_RemoveDuplicate) AS T
WHERE T.RowNumber > 1);

Check the result:

SELECT *FROM tbl_RemoveDuplicate;
 id | name
----+------
  1 | ABC
  2 | XYZ
  4 | RFQ
  5 | PQR
  6 | EFG
(5 rows)

Check the below input data and require output data to find order which step is 0 with status D and for the same order other status are P.

Input Data:

OrderID Step        Status
------- ----------- ------
ABC     0           D
ABC     1           P
ABC     2           P
ABC     3           P
XYZ     0           D
XYZ     1           D
EFQ     0           D

Expected Output:

OrderID
-------
ABC

Create a table with sample data:

CREATE TABLE tbl_Orders
(
	OrderID CHAR(5) 
	,Step INTEGER 
	,Status CHAR(1) 
)
GO 

INSERT INTO tbl_Orders
VALUES
('ABC', 0, 'D'),
('ABC', 1, 'P'),
('ABC', 2, 'P'),
('ABC', 3, 'P'),
('XYZ', 0, 'D'),
('XYZ', 1, 'D'),
('EFQ', 0, 'D'),
('EFQ', 1, 'D')
GO

Solution 1: Using CTE

with ctetest as 
( 
SELECT OrderID,Step,Status FROM tbl_Orders WHERE Step = 0 and Status = 'D'
)
select distinct a.OrderID from ctetest a inner join tbl_Orders b on a.OrderID = b.OrderID and b.Status = 'P'

Solution 2: Using GROUP BY .. Having

SELECT OrderID 
FROM tbl_Orders
GROUP BY OrderID
HAVING COUNT(*) =    
COUNT(CASE WHEN Step <> 0 AND Status = 'P' THEN 1 ELSE NULL END) 
+ COUNT(CASE WHEN Step = 0 AND Status = 'D' THEN 1 ELSE NULL END)

Please try the different solutions for this puzzle and share it via comment...

When we are working with different versions of database, database professionals are comparing the objects between databases of SQL Server.
They must make sure about that all databases are in sync.

Using this T-SQL Script, you can compare two databases and find a list of unmatched objects like: Constraints, Tables, Views, Stored Procedure, Triggers.

Sample demonstration:
First, Create two sample databases:

CREATE DATABASE ABC
GO
CREATE DATABASE XYZ
GO

Create few sample tables in both the databases:

CREATE TABLE ABC.dbo.tbl_Test
(
	ID INT
	,MyDate DATE
)
GO

CREATE TABLE ABC.dbo.tbl_MyTest
(
	ID INT
	,Name VARCHAR(50)
)
GO

CREATE TABLE XYZ.dbo.tbl_Test
(
	ID INT
	,MyDate DATE
)
GO

CREATE TABLE XYZ.dbo.tbl_MyFinal
(
	ID INT
	,Name VARCHAR(50)
)
GO

T-SQL Script to compare objects between two databases:
According to your databases, You can change the name of @SourceDatabase and @DestinationDatabase.

DECLARE @SourceDatabase VARCHAR(50) 
DECLARE @DestinationDatabase VARCHAR(50) 
DECLARE @SQL VARCHAR(MAX) 
     
SELECT @SourceDatabase = 'ABC' 
SELECT @DestinationDatabase = 'XYZ'
     
SELECT @SQL = 
'
	SELECT 
		ISNULL(S.name,D.name) ObjectName
		,CASE  
			WHEN S.object_id IS NULL 
				THEN D.type_desc + '' is missing in the Source Database: '	+ @SourceDatabase + ''' 
			WHEN D.object_id IS NULL 
				THEN S.type_desc +  '' is missing in the Destination Database: ' + @DestinationDatabase + ''' 
		END ''Status'' 
	FROM 
	(
		SELECT * FROM ' + @SourceDatabase + '.SYS.objects  
		WHERE Type_desc not in (''INTERNAL_TABLE'',''SYSTEM_TABLE'',''SERVICE_QUEUE'')
	) AS S  
	FULL OUTER JOIN 
	(
		SELECT * FROM ' + @DestinationDatabase + '.SYS.objects  
		WHERE Type_desc not in (''INTERNAL_TABLE'',''SYSTEM_TABLE'',''SERVICE_QUEUE'')
	) AS D 
	ON S.name = D.name 
		AND S.type = D.type 
	ORDER BY isnull(S.type,D.type)
'  
EXEC (@Sql)

The Result:

ObjectName                         Status
------------------  -------------------------------------------------------
tbl_Test              NULL
tbl_MyFinal           USER_TABLE is missing in the Source Database: ABC
tbl_MyTest            USER_TABLE is missing in the Destination Database: XYZ

Check the below input data and expected output to generate the group of sequences.

Input Data:

Name SeqNo
---- -----------
A    1
A    2
A    3
B    1
B    2
C    1
C    2
C    3
D    1
D    2
D    3
D    4
D    5

Expected Output:

Name SequenceNo_Groups
---- --------------------
A    11,12,13
A    11,12,13
A    11,12,13
B    21,22
B    21,22
C    31,32,33
C    31,32,33
C    31,32,33
D    41,42,43,44,45
D    41,42,43,44,45
D    41,42,43,44,45
D    41,42,43,44,45
D    41,42,43,44,45

Create a table with sample data:

CREATE TABLE TestSequences
(
	Name VARCHAR(3)
	,SeqNo INT
)
GO

INSERT INTO TestSequences
VALUES
('A' ,1)
,('A' ,2)
,('A' ,3)
,('B' ,1)
,('B' ,2)
,('C' ,1)
,('C' ,2)
,('C' ,3)
,('D' ,1)
,('D' ,2)
,('D' ,3)
,('D' ,4)
,('D' ,5)
 GO

Solution:

;WITH CTE AS
(
    SELECT b.Name , CAST(rnk  * 10 + SeqNo AS VARCHAR(3)) rnk FROM
    (
        SELECT * , ROW_NUMBER() OVER ( ORDER BY (SELECT NULL) )  rnk  FROM
        (
            SELECT DISTINCT Name FROM TestSequences
        ) a
    ) b
    INNER JOIN TestSequences a on b.Name = a.Name
)
SELECT Name, STUFF ((SELECT ',' + rnk FROM CTE w WHERE w.Name = t.Name FOR XML PATH('')) , 1,1,'') SequenceNo_Groups
FROM CTE t

Please try the different solution for this puzzle and share it via comment...

In this post, I am sharing an example of applying Full Text Search on PostgreSQL Table with Index.

Here, I am using tsvector for full text search which is document type and uses match operator like @@.

PostgreSQL: Example of Trigram Index for Full Text Search using pg_trgm Extension

Below is an example:

Create a sample table with data:

CREATE TABLE tbl_Textdata
(id int, txt character varying);

INSERT INTO tbl_Textdata VALUES
(1,'I am DBA'),(2,'database research & development'),(3,'think for data only')
,(4,'data is important'),(5,'data is a future'),(6,'I am data owner');

Do Full Text Searching:

SELECT txt
FROM tbl_Textdata
WHERE to_tsvector(txt) @@ to_tsquery('data');

Result:

txt
--------------------------
'think for data only'
'data is important'
'data is a future'
'I am data owner'

Apply an Index on require Text Pattern:

CREATE INDEX tbl_Textdata_txt_idx ON tbl_Textdata USING GIN (to_tsvector('english',txt));

Check the execution plan:

explain analyze
SELECT txt
FROM tbl_Textdata
WHERE to_tsvector(txt) @@ to_tsquery('data');

'Seq Scan on tbl_textdata  (cost=0.00..4.07 rows=1 width=32) (actual time=0.043..0.058 rows=4 loops=1)'
'  Filter: (to_tsvector((txt)::text) @@ to_tsquery('data'::text))'
'  Rows Removed by Filter: 2'
'Planning time: 5.494 ms'
'Execution time: 0.083 ms'

Check the below input data and expected output to generate the report on range basis on the common combination of SendFlag and ReceiveFlag.

Input Data:

ID          CreationDate SendFlag ReceiveFlag
----------- ------------ -------- -----------
1           2016-08-08   0        0
2           2016-10-01   0        0
3           2016-11-26   1        0
4           2016-12-26   1        0
5           2017-01-08   1        0
6           2017-03-10   1        1
7           2017-06-20   1        1
8           2017-08-15   0        1

Expected Output:

StartID     EndID       SendFlag ReceiveFlag
----------- ----------- -------- -----------
1           2           0        0
3           5           1        0
6           7           1        1
8           8           0        1

Create a table with sample data:

CREATE TABLE Flags
(
	ID INT 
	,CreationDate DATE
	,SendFlag BIT
	,ReceiveFlag BIT
)
GO
 
INSERT INTO Flags 
VALUES
(1,'20160808',0,0)
,(2,'20161001',0,0)
,(3,'20161126',1,0)
,(4,'20161226',1,0)
,(5,'20170108',1,0)
,(6,'20170310',1,1)
,(7,'20170620',1,1)
,(8,'20170815',0,1)
GO

Solution:

;WITH CTE1 AS
(
    SELECT f.*, ROW_NUMBER() OVER (ORDER BY f.ID) rnk
    FROM Flags f left JOIN Flags f2 on f.id + 1 = f2.id and f.SendFlag = f2.SendFlag and f.ReceiveFlag  = f2.ReceiveFlag
    WHERE f2.ID IS NULL
),
CTE2 AS
(
    SELECT f2.*,ROW_NUMBER() OVER (ORDER BY f2.ID) rnk
    FROM Flags f RIGHT JOIN Flags f2 on f.id = f2.id - 1 and f.SendFlag = f2.SendFlag and f.ReceiveFlag  = f2.ReceiveFlag
    WHERE f.ID IS NULL
)
SELECT c2.ID as StartID,c1.ID as EndID,c1.SendFlag,c2.ReceiveFlag 
FROM CTE1 c1 INNER JOIN CTE2 c2 on c1.rnk = c2.rnk

Please try the different solution for this puzzle and share it via comment...

We all are aware about the ACID Properties of Database System (Atomicity, Consistency, Isolation, Durability).
If you don’t know about the ACID, please visit below article.

ACID Properties in Database System (Atomicity, Consistency, Isolation, Durability)

In last one decade, lots of new Database Products available in the Market. The types are: RDBMS Products, NoSQL Products, BIGDATA, MPP Products.

My Question is, how do you choose best database product for your project?

Traditional Answer, The first preference of Database Designer would be ACID Properties oriented Databases.

But most of the NoSQL Databases are not providing full support of ACID Properties, then also NoSQL Databases are popular and People are using it for different purposes.

Because most of the NoSQL Databases are not ACID oriented, but they are CAP oriented.

What is CAP theorem (Consistency, Availability, Partition)?

CAP Published by Eric Brewer in 2000, the theorem is a set of basic requirements that describe any distributed system like: NoSQL Cassandra, MongoDB, CouchDB.

Consistency:

All nodes can see the same data at the same time. The data are the same across the cluster, so you can read or write any node.

Each transaction start and end in consistent stats so that all nodes can access the same data. Actually, It is achieved by update all nodes before reading.

Availability:

Here, The meaning of Availability is to access cluster in any situation like: server goes down, server delay. The system should always respond to a request, even if data is not in sync or inconsistent state, It prints the message like “This cluster data are not updated”.

Partition:

Here, the meaning of Partition is to avoid any type of system failure and system should run with available nodes or data. It does not allow any single point of failure because data replicated across all the clusters.

The Partition can work with Consistency (CP) or can work with Availability (AP) means, you can never find any Database System which follows the full CAP theorem.

Storage System with Partition and Consistency (CP):
Redis, MongoDB, AppFabric Caching, and MemcacheDB.
Storage System with Partition and Availability (AP):
Cassandra, DynamoDB, and CouchDB.

THE SERIALIZABLE Isolation level is one kind of extended version of the REPEATABLE READ Isolation level.
Now with the SERIALIZABLE Isolation level, you cannot modify the data while another transaction is reading the same data.

For SELECT-only transactions, use the SERIALIZABLE isolation level when you do not want to see the other transaction commits during your transaction.

For UPDATE and DELETE transactions, SERIALIZABLE isolation prevents concurrent modification of the same data row; it should therefore be used with caution.

Create a table with few sample records:

CREATE TABLE tbl_Employee
(
	EmpID INTEGER
	,EmpName VARCHAR(50)
);
 
INSERT INTO tbl_Employee
VALUES 
(1,'Anvesh'),(2,'Neevan')
,(3,'Roy'),(4,'Martin');

Execute in this current session. e.g. Session – A:

BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;  

UPDATE tbl_Employee SET EmpName ='Varlin' WHERE EmpID=4;

SELECT *FROM tbl_Employee;

 empid | empname
-------+---------
     1 | Anvesh
     2 | Neevan
     3 | Roy
     4 | Varlin

Execute in anohter session, e.g. Session – B:

UPDATE tbl_Employee SET EmpName ='Loother' WHERE EmpID=3;

SELECT *FROM tbl_Employee;

 empid | empname
-------+---------
     1 | Anvesh
     2 | Neevan
     4 | Varlin
     3 | Loother

Execute in anohter session, e.g. Session – C:

INSERT INTO tbl_Employee
VALUES (5,'Mahi');

SELECT *FROM tbl_Employee;

 empid | empname
-------+---------
     1 | Anvesh
     2 | Neevan
     4 | Martin
     3 | Loother
     5 | Mahi

Execute COMMIT on first Current Session – A:

--Nothing happen to this Query and Data is as it is. 

SELECT *FROM tbl_Employee; 

 empid | empname
-------+---------
     1 | Anvesh
     2 | Neevan
     3 | Roy
     4 | Varlin

-- Now Execute COMMIT:
COMMIT TRANSACTION;

In this post, I am sharing a script for checking the Network and Connect related permission of SQL Server User.

When you installed the SQL Server, for network access you should enable the TCP/IP pipeline and other connect permission so that others can access the server.

Using below script, you can easily identify those permissions which are important for connecting SQL Server. I took the reference from this official page.

SELECT 
	EP.name, 
	SP.STATE,   
	CONVERT(nvarchar(38), suser_name(SP.grantor_principal_id)) AS GRANTOR,   
	SP.TYPE AS PERMISSION,  
	CONVERT(nvarchar(46),suser_name(SP.grantee_principal_id)) AS GRANTEE   
FROM sys.server_permissions SP, sys.endpoints EP  
WHERE SP.major_id = EP.endpoint_id  
ORDER BY Permission,grantor, grantee

Check the below input data and expected output to prepare the report on bank account transaction like generate the data of AccountBalance column where for CR plus the transaction value and for DR minus the transaction value.

Input Data:

TransactionDate AccName    Type Amount
--------------- ---------- ---- -------------
2017-01-01      Anvesh     CR   60000.00
2017-02-01      Anvesh     DB   8000.00
2017-03-01      Anvesh     CR   8000.00
2017-04-01      Anvesh     DB   5000.00
2017-01-01      Nupur      CR   10000.00
2017-02-02      Nupur      CR   8000.00
2017-03-03      Nupur      DB   8000.00

Expected Output:

TransactionDate AccName    Type Amount                AccountBalance
--------------- ---------- ---- --------------------- ---------------
2017-01-01      Anvesh     CR   60000.00              60000.00
2017-02-01      Anvesh     DB   8000.00               52000.00
2017-03-01      Anvesh     CR   8000.00               60000.00
2017-04-01      Anvesh     DB   5000.00               55000.00
2017-01-01      Nupur      CR   10000.00              10000.00
2017-02-02      Nupur      CR   8000.00               18000.00
2017-03-03      Nupur      DB   8000.00               10000.00

Create a table with sample data:

CREATE TABLE AccountBalance
(
	TransactionDate DATE
	,AccName VARCHAR(10)
	,Type VARCHAR(2)
	,Amount MONEY
)
GO

INSERT INTO AccountBalance
VALUES
('2017-01-01','Anvesh','CR','60000')
,('2017-02-01','Anvesh','DB','8000')
,('2017-03-01','Anvesh','CR','8000')
,('2017-04-01','Anvesh','DB','5000')
,('2017-01-01','Nupur','CR','10000')
,('2017-02-02','Nupur','CR','8000')
,('2017-03-03','Nupur','DB','8000')
GO

Solution:

;WITH CTE AS
(
    SELECT TransactionDate , AccName , Type 
            , CASE WHEN Type = 'DB' THEN AMOUNT * -1 ELSE AMOUNT END Amount, Amount Amt
            ,ROW_NUMBER() OVER (PARTITION BY AccName ORDER BY (SELECT NULL)) rnk
    FROM AccountBalance
)
SELECT  TransactionDate , AccName , Type , Amt Amount
, (SELECT SUM(Amount) FROM CTE c2 WHERE c2.AccName = c1.AccName AND c2.rnk <= c1.rnk ) AccountBalance
FROM CTE c1

Please try the different solution for this puzzle and share it via comment...