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How to avoid duplicate records in SQL joins?
Without your data I’ll need to guess. You’re using INNER JOIN – which means no record returns if it fails to find a match. It is very common, therefore, to return few than all of your rows – especially with so many joins, each having the potential to eliminate some rows.
Why are there duplicates in the things table?
Giving you a total of 4 records. If you want to join these together, you need some unique way of identifying the rows between the tables. You are getting duplicates because both records in the Things table have a BNO-CSCcode of 5560-04020, as do both records in the Mapp table.
Why are there no duplicates on inner join?
Now if I join the table on recid, it will give 0 result, there will be no duplicates because recid is unique. But if I join on firstname and lastname column, which are not unique and there are duplicates, I get duplicates on inner join.
Is it possible to eliminate duplication in a join?
So, if you use the following query: …you should eliminate the duplication. However, using a field that is obviously a text field in a join is not best practice, as if they are separately user-generated, they are unlikely to match, and it takes longer (relatively speaking) to match fields with a higher byte-count than those with low byte-counts.
Is there a way to avoid duplicate on joining two tables?
They won’t be. Re-arranging steps like that is a major part of optimization. And in fact, for non- INNER joins, putting the filter in the ON clause makes the query slower since it has to include more rows from the unfiltered table. Yes, that’s a different result set, but it’s also rarely needed.
How to check for duplicate rows in a table?
You have duplicate rows because there are duplicate in table1 or table 2. The scrpit should be: Copy Code. select a.comm, b.fee from table1 a inner join table2 b on a.country=b.country. Note that the where condition is not needed. To check for duplicate run the script: Copy Code.