Question: How do I join two tables in SQL without duplicates?

The SQL UNION ALL operator is used to combine the result sets of 2 or more SELECT statements. It does not remove duplicate rows between the various SELECT statements (all rows are returned). Each SELECT statement within the UNION ALL must have the same number of fields in the result sets with similar data types.

How do I prevent duplicate rows from joining multiple tables?

The GROUP BY clause at the end ensures only a single row is returned for each unique combination of columns in the GROUP BY clause. This should prevent duplicate rows being displayed in your results.

How do you remove duplicates from two tables in SQL?


  1. In the output above, we have two duplicate records with ID 1 and 3. …
  2. To remove this data, replace the first Select with the SQL delete statement as per the following query. …
  3. SQL delete duplicate Rows using Common Table Expressions (CTE) …
  4. We can remove the duplicate rows using the following CTE.
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How do you prevent duplicates in SQL query?

5 Easy Ways How to Avoid Duplicate Records in SQL INSERT INTO SELECT

  1. Adding the Distinct Keyword to a Query to Eliminate Duplicates. …
  2. Using SQL WHERE NOT IN to Remove Duplicate Values. …
  3. Using INSERT INTO WHERE NOT IN SQL Operator. …
  5. Using COUNT(*) = 0 Without Duplicates.

Can we join two tables without any relation?

The answer to this question is yes, you can join two unrelated tables in SQL, and in fact, there are multiple ways to do this, particularly in the Microsoft SQL Server database. The most common way to join two unrelated tables is by using CROSS join, which produces a cartesian product of two tables.

How do you eliminate duplicate rows in Join?

Solution. 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.

Why am I getting duplicate rows in SQL?

You are getting duplicates because more than one row matches your conditions. To prevent duplicates use the DISTINCT keyword: SELECT DISTINCT respid, cq4_1, dma etc… If you do not have duplicates in preweighting_data before then the only other chance is, that the column us_zip.

What is query for second highest salary?

We can nest the above query to find the second largest salary. select *from employee group by salary order by salary desc limit 1,1; There are other ways : SELECT name, MAX(salary) AS salary FROM employee WHERE salary IN (SELECT salary FROM employee MINUS SELECT MAX(salary) FROM employee);

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How do you remove duplicates without using distinct in SQL?

Below are alternate solutions :

  1. Remove Duplicates Using Row_Number. WITH CTE (Col1, Col2, Col3, DuplicateCount) AS ( SELECT Col1, Col2, Col3, ROW_NUMBER() OVER(PARTITION BY Col1, Col2, Col3 ORDER BY Col1) AS DuplicateCount FROM MyTable ) SELECT * from CTE Where DuplicateCount = 1.
  2. Remove Duplicates using group By.

How do I combine two SQL query results?

To combine two or more SELECT statements to form a single result table, use the set operators: UNION, EXCEPT or INTERSECT.

To eliminate redundant duplicate rows when combining result tables, specify one of the following keywords:


How do I select duplicate rows 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 duplicates in SQL?

To select duplicate values, you need to create groups of rows with the same values and then select the groups with counts greater than one. You can achieve that by using GROUP BY and a HAVING clause.

Does GROUP BY remove duplicates?

GROUP BY does not “remove duplicates”. GROUP BY allows for aggregation. If all you want is to combine duplicated rows, use SELECT DISTINCT.

Can we join two tables without common columns?

Yes, you can! The longer answer is yes, there are a few ways to combine two tables without a common column, including CROSS JOIN (Cartesian product) and UNION. The latter is technically not a join but can be handy for merging tables in SQL.

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How do I join two tables together?

1. Click on the table you want to drag, then the cross sign will be appeared, then click the cross sign to select the whole table. 2. Press Shift + Alt + Up arrow until the selected table is joined to above one.

Can two tables have same primary key?

Every table can have (but does not have to have) a primary key. The column or columns defined as the primary key ensure uniqueness in the table; no two rows can have the same key. The primary key of one table may also help to identify records in other tables, and be part of the second table’s primary key.

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