Why I am getting duplicate records in SQL join?

Why I am getting duplicate records in SQL join?

You may have join duplicates (in SQL) if your data is case-sensitive because an “A” will be treated the same way as an “a”, violating the uniqueness we require on the join key.

How prevent duplicate rows in SQL join?

The keyword DISTINCT is used to eliminate duplicate rows from a query result: SELECT DISTINCT FROM A JOIN B ON However, you can sometimes (possibly even ‘often’, but not always) avoid the need for it if the tables are organized correctly and you are joining correctly.

How do you eliminate duplicate rows in join?

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.

Will LEFT join cause duplicates?

Avoiding Duplicates Again, if we perform a left outer join where date = date, each row from Table 5 will join on to every matching row from Table 4. However, in this case, the join will result in 4 rows of duplicate dates in the joined DataSet (see Table 6).

Why is my SQL query returning duplicate rows?

If you do not include DISTINCT in a SELECT clause, you might find duplicate rows in your result, because SQL returns the JOB column’s value for each row that satisfies the search condition. Null values are treated as duplicate rows for DISTINCT.

How remove duplicates in join SQL Server?

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.

How do you delete duplicate records in SQL query?


  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.

How do you delete duplicate records in SQL Server?

To delete the duplicate rows from the table in SQL Server, you follow these steps:

  1. Find duplicate rows using GROUP BY clause or ROW_NUMBER() function.
  2. Use DELETE statement to remove the duplicate rows.

Does full outer join give duplicates?

Suppose there are duplicate records in the tables (remove the primary key and insert twice to create this situation). UNION eliminates duplicates, which a full join doesn’t do.

Will Inner join allow duplicates?

1 Answer. Yes, if there are duplicate values.

Why is access duplicating records?

Duplicate data often creeps in when multiple users add data to the Access database at the same time or if the database wasn’t designed to check for duplicates. Duplicate data can be either multiple tables containing the same data or two records containing just some fields (columns) with similar data.

How do I join the same table in SQL?

To construct a self join, you select from the same table twice by using the SELECT statement with an inner join or outer join clause. Because you refer to the same table twice in the same statement, you have to use table aliases.

What is simple Join SQL?

A SQL JOIN is performed whenever two or more tables are listed in a SQL statement. There are 4 different types of SQL joins: SQL INNER JOIN (sometimes called simple join) SQL LEFT OUTER JOIN (sometimes called LEFT JOIN)

What does join_by_SQL do?

Join (SQL) Sample tables. Relational databases are usually normalized to eliminate duplication of information such as when entity types have one-to-many relationships. Cross join. CROSS JOIN returns the Cartesian product of rows from tables in the join. Inner join. Outer join. Self-join. Alternatives. Implementation. See also References. External links.

What is the inner join in SQL?

SQL-INNER JOINS. The most important and frequently used of the joins is the INNER JOIN. They are also referred to as an EQUIJOIN. The INNER JOIN creates a new result table by combining column values of two tables (table1 and table2) based upon the join-predicate.