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I have a table in SQL Server 2005 containing 10000054 records; these records are inserted through a bulk insert operation. The table does not contain a primary key and I want to have one. If I try to modify the table's structure, adding a new column, PK, set as int with isidentity, the management console gives me a warning:
"Changes to tables with large amounts of data could take a considerable amount of time. While changes are being saved, table data will not be accessible."
then outputs error:
" Unable to modify table. Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. "
I want a PK into my table.
How can I add it?
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If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s). Note − You would use these concepts while creating database tables.
Because a table can have only one primary key, you cannot add a primary key to a table that already has a primary key defined. To change the primary key of a table, delete the existing key using a DROP clause in an ALTER TABLE statement and add the new primary key.
Many-to-many relationshipsThe primary key of the junction table consists of the foreign keys from both table A and table B. For example, the "Authors" table and the "Titles" table have a many-to-many relationship that is defined by a one-to-many relationship from each of these tables to the "TitleAuthors" table.
We can set PRIMARY KEY constraint on multiple columns of an existing table by using ADD keyword along with ALTER TABLE statement.
You can use the ALTER statement to create a primary key. However, the primary key can only be created on columns that are defined as NOT NULL. You cannot create a primary key on a column that allows NULLs. If you need to do, you have to drop and recreate the table. We have added a primary key constraint to an already existing table.
A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields). The following SQL creates a PRIMARY KEY on the "ID" column when the "Persons" table is created:
Create Primary Key in Access 1 In Object Explorer, right-click the table to which you want to add a unique constraint, and click Design. 2 In Table Designer, click the row selector for the database column you want to define as the primary key. ... 3 Right-click the row selector for the column and select Set Primary Key. See More....
Let's create a Table with One Column as a SQL Primary Key. Step 1) Run the Query by clicking on 'Execute.' Result: Course_Id is now a Primary Key. Example: Let's see if it allows entering Multiple Records with Same Course ID. Step 2) Verify all Data Inserted successfully by running the Select query.
If in Management Studio you set the primary key in Design view (without saving), when you next right click you have an option "Generate Change Script" - this option is also available on the "Table Designer" menu at the top.
That provides the raw SQL (safely wrapped in a transaction) which you can copy to clipboard, take that over to run as a New Query (button top left, or File > New > Query with Current Connection), paste it in, select the right DB and execute the query.
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