composite-key

I have a table defined in web2py db.define_table( 'pairing', Field('user',writable=True,readable=True), Field('uid', writable=True , readable=True) ) This table needs to have user and uid combination being unique. I have looked through the web2py documentation , but there isn't direct way to define composite key . How do we define composite way in web2py It depends on what you are trying to do. By default, web2py automatically creates an auto-incrementing id field to serve as the primary key for each table, and that is the recommended approach whenever possible. If you are dealing with a

Since IF EXISTS isn't supported by MySQL I am struggling to think of the syntax for doing something like the following pseudo in MySQL: IF ((select count(*) from table where col1='var1' AND col2='var2' AND col3='var3' AND col4='var4' AND col5='var5')>0) then combination of vars exist in record - do a thing; ELSE combination of vars does not exist in record - insert record; END IF; I should have thought CASE would suit this but for life of me I'm unable to think of the correct syntax. I'd use unique indexes but every one of the columns needs to allow duplicates, it's only a matching combination

I've to test different datamodels for Cassandra. I'm thinking about to use a composite key made by key1:key2 for the row key. With this configuration on Cassandra, for example, I can query to have all the rows having a specific key1 value and any key2 value but It's impossible otherwise (obtain all the rows having a specific key2's value and any key1). Is it right? thanks in advance Cesare libjack If you use Order Preserving Partitioning (OPP), then yes, the keys will be stored sorted, and then you can get slices over a range of keys e.g. A:A to A:Z -- but not necessarily any:A to any:Z. But,

I have a table which contains only 2 fields. The table has a composite PK formed by these two fields. When using Netbeans for creating entity beans from database, the entity bean is not created automatically like other tables that have more than 2 fields. So I guess I need to create the entity bean myself. What is the best practice for creating this entity bean? Does it have to contain COMPOSITE KEY object or not? Xavi López I don't use NetBeans so I can't really say anything about its mapping tools. For mapping a composite key, there are a couple of options. You can Define a separate

My Parent class has two child classes: Child and ParentHobby . The Child class has a singular PK and the @OneToMany mapping on it works. The problem is that I don't know how to map it on the ParentHobby class, which has a composite PK. Parent: //this works @OneToMany(cascade = CascadeType.ALL, mappedBy = "parent", fetch = FetchType.EAGER) private List<Child> childList; //this DOES NOT work @OneToMany(cascade = CascadeType.ALL, mappedBy = "parent", fetch = FetchType.EAGER) private List<ParentHobby> hobbyList; Child: @Entity @Table(name="CHILD") public class Child { @Id @SequenceGenerator(name=