What is duplicate value SQL?

Asked By: Laetitia Hariscain | Last Updated: 23rd May, 2020
Category: technology and computing databases
4.3/5 (80 Views . 28 Votes)
Duplicate records in SQL, also known as duplicate rows, are identical rows in an SQL table. This means, for a pair of duplicate records, the values in each column coincide.

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People also ask, how do I find duplicates in SQL?

How it works:

  1. First, the GROUP BY clause groups the rows into groups by values in both a and b columns.
  2. Second, the COUNT() function returns the number of occurrences of each group (a,b).
  3. Third, the HAVING clause keeps only duplicate groups, which are groups that have more than one occurrence.

Beside above, how do I find duplicate records? To do so:

  1. Select the range of cells you wish to test.
  2. On Excel's Home tab, choose Conditional Formatting, Highlight Cells Rules, and then Duplicate Values.
  3. Click OK within the Duplicate Values dialog box to identify the duplicate values.
  4. Duplicate values in the list will now be identified.

Similarly, it is asked, what is duplicate query?

A find duplicates query allows you to search for and identify duplicate records within a table or tables. A duplicate record is a record that refers to the same thing or person as another record.

How can I delete duplicate rows?

Remove duplicate values

  1. Select the range of cells, or ensure that the active cell is in a table.
  2. On the Data tab, click Remove Duplicates .
  3. In the Remove Duplicates dialog box, unselect any columns where you don't want to remove duplicate values.
  4. Click OK, and a message will appear to indicate how many duplicate values were removed.

24 Related Question Answers Found

How do you delete duplicates in SQL?

  1. 1) First identify the rows those satisfy the definition of duplicate and insert them into temp table, say #tableAll .
  2. 2) Select non-duplicate(single-rows) or distinct rows into temp table say #tableUnique.
  3. 3) Delete from source table joining #tableAll to delete the duplicates.

How do I select without duplicates in SQL?

SQL SELECT DISTINCT Statement
  1. SELECT DISTINCT returns only distinct (different) values.
  2. SELECT DISTINCT eliminates duplicate records from the results.
  3. DISTINCT can be used with aggregates: COUNT, AVG, MAX, etc.
  4. DISTINCT operates on a single column. DISTINCT for multiple columns is not supported.

How do you remove duplicates without using distinct?

Method 1: SELECT col1, col2, col3 ….. --(list all the columns for which you want to eliminate duplicates) FROM (SELECT col1, col2, col3,….. --(list all the columns as above), COUNT(*) FROM table) Method 2: SELECT col1, col2, col3 ….. --(list all the columns for which you want to eliminate duplicates) FROM table UNION

How do I count rows in SQL?

Counting all of the Rows in a Table. To counts all of the rows in a table, whether they contain NULL values or not, use COUNT(*). That form of the COUNT() function basically returns the number of rows in a result set returned by a SELECT statement.

How can we find second highest salary in SQL?


SELECT Salary FROM (SELECT Salary FROM Employee ORDER BY salary DESC LIMIT 2) AS Emp ORDER BY salary LIMIT 1; In this solution, we have first sorted all salaries form Employee table in decreasing order, so that 2 highest salaries come at top of the result set. After that we took just two records by using LIMIT 2.

How do I find duplicate rows in SQL using Rowid?

After "SQL," enter "select * from names;" to see your rows. Delete duplicate rows by identifying their column. After "SQL'" enter "delete from names a where rowid > (select min(rowid) from names b where b.name=a.name and b. age=a.

What is duplicate query and unmatched query?

The Find Duplicates Query Wizard works on a single table, whereas the Find Unmatched Query Wizard compares records in one table with records in another.

How do you find duplicates in Access query?

Find duplicate records
  1. On the Create tab, in the Queries group, click Query Wizard.
  2. In the New Query dialog, click Find Duplicates Query Wizard > OK.
  3. In the list of tables, select the table you want to use and click Next.
  4. Select the fields that you want to match and click Next.

How do I filter duplicates in Access query?

Select the field that you want to make sure has unique values. In the Field Properties pane at the bottom of the table design view, on the General tab, set the Indexed property to Yes (No duplicates). Save the changes to your table.

How do I remove duplicate records in Access?


Hide duplicate values in a grouped Access report
  1. With the report in Design view, double-click the OrderID control to launch the properties sheet.
  2. Set the Hide Duplicates property to Yes.

What is the formula for finding duplicates in Excel?

How to identify duplicates in Excel
  1. Input the above formula in B2, then select B2 and drag the fill handle to copy the formula down to other cells:
  2. =IF(COUNTIF($A$2:$A$8, $A2)>1, "Duplicate", "Unique")
  3. The formula will return "Duplicates" for duplicate records, and a blank cell for unique records:

How do I find duplicates in postgresql?

1) How to find duplicates?
  1. Count(*) counts the number of rows in each group.
  2. In GROUP BY we can add the criterias (properties) by which we are looking for duplicates.
  3. The result is a table (firstname, lastname, count) containing the properties according which the groups were defined and the number of rows per group.

How do I find duplicates in Word?

Click the "More" button at the bottom of the window to view more options. Place a check mark in front of the "Find whole words only" option. Click the "Reading Highlight" button and then "Highlight All" to find all duplicate words and highlight them. Click "Close" to close the Find And Replace window.

How do you exclude duplicates in SQL?

The go to solution for removing duplicate rows from your result sets is to include the distinct keyword in your select statement. It tells the query engine to remove duplicates to produce a result set in which every row is unique. The group by clause can also be used to remove duplicates.

How do I count duplicate rows 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).

What does count (*) do in SQL?

COUNT(*) returns the number of rows in a specified table, and it preserves duplicate rows. It counts each row separately. This includes rows that contain null values.

How can I delete duplicate records in mysql?

Create a new table with the structure the same as the original table that you want to delete duplicate rows. Insert distinct rows from the original table to the immediate table. Drop the original table and rename the immediate table to the original table.