#primary-key

How-to: How to reset postgres' primary key sequence when it falls out of sync? #computers #dev #it

How to reset postgres’ primary key sequence when it falls out of sync?

I ran into the problem that my primary key sequence is not in sync with my table rows.

That is, when I insert a new row I get a duplicate key error because the sequence implied in the serial datatype returns a number that already exists.

It seems to be caused by import/restores not maintaining the sequence properly.

Answer [by

How to: Can I have multiple primary keys in a single table? #it #computers #programming

Can I have multiple primary keys in a single table?

Can I have multiple primary keys in a single table?

Answer [by HLGEM]: Can I have multiple primary keys in a single table?

A primary key is the key that uniquely identifies a record and is used in all indexes. This is why you can’t have more than one. It is also generally the key that is used in joining to child tables but this is not a…

Fixed Unable to update the EntitySet – because it has a DefiningQuery and no element exist #dev #it #asnwer

Unable to update the EntitySet – because it has a DefiningQuery and no <UpdateFunction> element exist

I am using Entity Framework 1 with .net 3.5.

I am doing something simple like this:

var RoomDetails = context.Rooms.ToList(); foreach (var Room in Rooms) { Room.LastUpdated = DateTime.Now; }

I am getting this error when I try to do:

context.SaveChanges();

I get the error:

Unable to update…

How to: Difference between Key, Primary Key, Unique Key and Index in MySQL

Difference between Key, Primary Key, Unique Key and Index in MySQL

When should I use KEY, PRIMARY KEY, UNIQUE KEY and INDEX?

Answer: Difference between Key, Primary Key, Unique Key and Index in MySQL

KEY and INDEX are synonyms.

You should add an index when performance measurements and EXPLAIN shows you that the query is inefficient because of a missing index. Adding an index can improve the…

Fixed Sqlite primary key on multiple columns #dev #it #asnwer

Sqlite primary key on multiple columns

What is the syntax for specifying a primary key on more than 1 column in SQLITE ?

Answer: Sqlite primary key on multiple columns

CREATE TABLE something ( column1 INTEGER NOT NULL, column2 INTEGER NOT NULL, value, PRIMARY KEY ( column1, column2) );

Answer: Sqlite primary key on multiple columns

Yes. But remember that such primary key allow NULLvalues in…

Fixed How to 'insert if not exists' in MySQL? #dev #it #asnwer

How to ‘insert if not exists’ in MySQL?

I started by googling, and found this article which talks about mutex tables.

I have a table with ~14 million records. If I want to add more data in the same format, is there a way to ensure the record I want to insert does not already exist without using a pair of queries (ie, one query to check and one to insert is the result set is empty)?

Does a unique

How to: Sql Server add auto increment primary key to existing table

Sql Server add auto increment primary key to existing table

As the title, I have an existing table which is already populated with 150000 records. I have added an Id column (which is currently null).

I’m assuming I can run a query to fill this column with incremental numbers, and then set as primary key and turn on auto increment. Is this the correct way to procede? And if so, how do I fill the…

How to: How to reset postgres' primary key sequence when it falls out of sync?

How to reset postgres’ primary key sequence when it falls out of sync?

I ran into the problem that my primary key sequence is not in sync with my table rows.

That is, when I insert a new row I get a duplicate key error because the sequence implied in the serial datatype returns a number that already exists.

It seems to be caused by import/restores not maintaining the sequence properly.

Answer:…