What is SQL?

SQL stands for Structured Query Language and becomes first off developed with the aid of IBM inside the 70s to engage with relational databases. It is the not unusual language for databases, remains quite readable and its miles especially easy to take a look at the basics (although the language may be very effective).             

How to Find and Delete Duplicates in SQL

According to database design first-class practices, a SQL Server table should not include reproduction rows. During the database layout technique, primary keys must be created to take away replica rows. However, once in a while we need to paintings with databases where these rules are not observed or exceptions are possible (whilst these rules are bypassed knowingly).

DISTINCT is useful in certain instances, but it has the drawback that it may growth load at the query engine to carry out the kind (since it needs to evaluate the end result set to itself to cast off duplicates).

Find and Remove Duplicates Using Row in SQL

A simple query for finding and removing the duplicates from the table using row numbers.

WITH CTE ( Col1 , Col2 , Col3 , DuplicateCount ) AS ( SELECT Col1, Col2, Col3, ROW_NUMBER( )

OVER ( PARTITION BY Col1 , Col2 , Col3


AS DuplicateCount

FROM MyTable )

SELECT * from CTE Where DuplicateCount = 1

Find and Remove Duplicates Using Self Join in SQL

A simple table schema is given below:

( emp_name    emp_address   sex         matial_status )

A Query:

SELECT emp_name , emp_address , relationship , marital_status

from MyTable a


select 1

from MyTable b

where   b.emp_name = a.emp_name AND

b.emp_address = a.emp_address AND
b.sex = a.sex AND
b.create_date > = a.create_date


Find and Removing using Group By in SQL

We can also find and remove duplicates data from a table using Group By clause in SQL. A simple example is given below:

SELECT FirstName , LastName , MobileNo , COUNT ( * ) AS CNT
GROUP BY FirstName , LastName , MobileNo
HAVING COUNT ( * ) = 1

How to Remove Duplicates in SQL Table

Let’s a simple table is given below:

Create a Table MyTable (

RowID int not null identity(1,1) primary key,

Col1 varchar(20) not null,

Col2 varchar(2048) not null,

Col3 tinyint not null


Now we delete duplicates from it.

COUNT ( * ) TotalCount
FROM MyTable
HAVING COUNT ( * ) > 1

Above query will delete the duplicates from RowID column.

Find and Remove Duplicates Using Row Value wise in SQL

Now using row wise , another simple example finding and removing duplicates in row wise:

DELETE TableName

WHERE id not in ( SELECT MAX ( id ) FROM TableName GROUP BY Value ) ;

We can improve our results using this query:

DELETE from TableName O

WHERE id < ( SELECT MAX ( columnName ) FROM TableName AS m                          

WHERE m.Value = O.Value GROUP BY Value ) ;

How do I remove duplicates from a query?

Keep or remove duplicate rows (Power Query)
  1. To open a query, locate one previously loaded from the Power Query Editor, select a cell in the data, and then select Query > Edit.
  2. Select a column by clicking the column header.
  3. Select Home > Remove Rows > Remove Duplicates.

How remove duplicates in SQL join?

Select column values in a specific order within rows to make rows with duplicate sets of values identical. Then you can use SELECT DISTINCT to remove duplicates. Alternatively, retrieve rows in such a way that near-duplicates are not even selected.

How do I delete duplicates but keep one?

Tip: You also can remove all duplicates but keep one with Select Duplicate & Unique Cells like this: Select all the unique values including the first duplicates, and then copy them by pressing Ctrl + C and paste to another location by Ctrl + V.

Can I remove duplicates in Excel?

Remove duplicate values

Select the range of cells that has duplicate values you want to remove. Tip: Remove any outlines or subtotals from your data before trying to remove duplicates. Click Data > Remove Duplicates, and then Under Columns, check or uncheck the columns where you want to remove the duplicates.

How do I remove duplicates from a list?

To remove the duplicates from a list, you can make use of the built-in function set(). The specialty of the set() method is that it returns distinct elements. You can remove duplicates from the given list by importing OrderedDictfrom collections.

How do I remove duplicates in multiple columns?

Remove Duplicates from Multiple Columns in Excel
  1. Select the data.
  2. Go to Data –> Data Tools –> Remove Duplicates.
  3. In the Remove Duplicates dialog box: If your data has headers, make sure the ‘My data has headers’ option is checked. Select all the columns except the Date column.

How do I remove duplicates in numbers?

How do I remove duplicates from a CSV file?

Open the CSV file on your computer in Excel. Highlight the column of the email addresses. Click on “Data” then choose “Sort: A to Z”. Next click on “Data” and choose ‘Remove duplicates‘ and all duplicates will be removed from the file.

How do you count duplicates in Excel?

Tip: If you want to count the duplicates in the whole Column, use this formula =COUNTIF(A:A, A2) (the Column A indicates column of data, and A2 stands the cell you want to count the frequency, you can change them as you need).

How do I count duplicates in SQL?

How to Find Duplicate Values in SQL
  1. Using the GROUP BY clause to group all rows by the target column(s) – i.e. the column(s) you want to check for duplicate values on.
  2. Using the COUNT function in the HAVING clause to check if any of the groups have more than 1 entry; those would be the duplicate values.

How do you use Countifs?

Excel COUNTIFS Function
  1. Summary. The Excel COUNTIFS function returns the count of cells that meet one or more criteria.
  2. Count cells that match multiple criteria.
  3. The number of times criteria are met.
  4. =COUNTIFS (range1, criteria1, [range2], [criteria2], )
  5. range1 – The first range to evaulate.
  6. Excel 2007.

Is Countifs AND or OR?

The tutorial explains how to use Excel’s COUNTIF and COUNTIFS functions to count cells with multiple OR as well as AND conditions. As everyone knows, Excel COUNTIF function is designed to count cells based on just one criterion while COUNTIFS evaluates multiple criteria with AND logic.

Why is Countifs not working?

This is a common issue related to many other Excel functions like SUMIF, SUMIFS, COUNTBLANK, etc. SOLUTION: To fix the COUNTIF #Value error, open the linked workbook specifies in the formula and hit F9 to refresh the formula. Doing this will fix the #value error.

What is difference between Countif and Countifs?

The difference is that COUNTIF is designed for counting cells with a single condition in one range, whereas COUNTIFS can evaluate different criteria in the same or in different ranges.