Why does PostgreSQL duplicate key violate the unique constraint?

Why does PostgreSQL duplicate key violate the unique constraint?

The problem is that i have a table and a column “id” i want it to be unique number just as normal. This type of column is serial and the next value after each insert is comming from a sequence so everything seems to be all right but it still sometimes showing this error. I dont know why ?

Is it necessary to add a unique constraint to PostgreSQL?

Adding another unique constraint isn’t necessary to do that. The “duplicate key” error is telling you that the work was not done because it would produce a duplicate key, not that it discovered a duplicate key already commited to the table. From http://www.postgresql.org/docs/current/interactive/datatype.html.

Is there way to find all duplicate records in PostgreSQL-stack?

The unique constraint is currently the first field called “id”, however I am now looking to add a constraint to make sure the year, user_id, sid and cid are all unique but I cannot apply the constraint because duplicate values already exist which violate this constraint. Is there a way to find all duplicates?

When to use conflict do nothing in PostgreSQL?

For future searchs, use ON CONFLICT DO NOTHING. The primary key is already protecting you from inserting duplicate values, as you’re experiencing when you get that error. Adding another unique constraint isn’t necessary to do that.

Why do I get the error duplicate key?

At a later point some records are inserted without id and they fail with the error: Error: duplicate key value violates unique constraint. Apparently the id got defined as a sequence: Each failed insert increases the pointer in the sequence till it increments to a value that no longer exists and the queries succeed.

When do you get unique violation in PostgreSQL?

So, if, for example, you imported 10 users, you have users with ids 1-10, but your sequence is still at 1. When you attempt to create a new user without specifying the id, it pulls the value from the sequence (1), and you get a unique violation because you already have a user with id 1.

How to avoid ” error : duplicate key ” error?

INSERT INTO “jos_content” VALUES (1,36,’About’,…) At a later point some records are inserted without id and they fail with the error: Error: duplicate key value violates unique constraint. Each failed insert increases the pointer in the sequence till it increments to a value that no longer exists and the queries succeed.

How to avoid duplicate key in table structure?

Your INSERT statement is the problem. With your id column defined as serial, you shouldn’t insert manual values for id. Those may collide with the next value from the associated sequence. Provide an explicit list of target columns (which is almost always a good idea for persisted INSERT statements) and omit serial columns completely.