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1 Σεπ 2012 · You could add DISTINCT or GROUP BY to the query to prevent duplicates. If the final table already has some data prior to this population, you may also want to add a correlated NOT EXISTS. For example:
In this tutorial, you will learn about Db2 primary key and how to use the PRIMARY KEY constraint to define a primary key for a table.
Right-click the table you want to modify, and select Alter from the pop-up menu. On the Keys page, select one or more columns as primary keys. Optional: Enter the constraint name of the primary key. You can use the Control Center or the ALTER TABLE statement to add primary keys.
You can use primary key and foreign key constraints to define relationships between tables. A primary key is a column or combination of columns that has the same properties as a unique constraint.
A primary key is a special type of unique key and cannot contain null values. For example, the DEPTNO column in the DEPT table is a primary key. A table can have no more than one primary key. Primary keys are optional and can be defined in CREATE TABLE or ALTER TABLE statements.
20 Οκτ 2018 · This db2 query: alter table mylib.mytable add primary key(field1, field2, field3) returns [SQL0624] Table MYTABLE in MYLIB already has a primary key'. However alter table mylib.mytable drop
5 Αυγ 2019 · If you try to add a primary key to a column that is nullable, you’ll get an error. To demonstrate this, let’s create another table, but this time, we’ll also forget to specify the column as NOT NULL :
