So far I have not found a better/shorter way to check if a table entry exists than the following:
let exists = await SELECT(1).from(Books,201)
return (exists .length > 0) ? true : false
Found here: https://cap.cloud.sap/docs/node.js/cds-tx#cds-tx-ctx-fn
https://www.w3resource.com/sql/aggregate-functions/Max-with-group-by.php
entity myEntity {
key ID: Integer;
key seqNr: Integer;
key createdAt: DateTime;
...
}
@readonly
entity myEntityMaxSeqNr
as select from myEntity {
ID,
count(seqNr) as maxSeqNr: Integer
createdAt,
...
}
group by
ID,
createdAt;
This can also be done using CQL like here.
Since there is nothing in the official CAP documentation about min and max functions, I figured out the following syntax:
const result1 = await cds.run(`SELECT *, MAX(seqNr) FROM ${myTable} LIMIT 1`) //returns array
const result2 = await SELECT.one.from(myTable, [`MAX(seqNr)`]).columns('*') //returns object
const result3 = await SELECT.one.from(myTable).columns('MAX(seqNr)') //returns object containing only the max counter value
In the documentation they always use a star in string literals like this o => o.`*` to select all fields, but when running this it always failed. However, after some tests I found that this format works with brackets o => o.('*')
https://cap.cloud.sap/docs/guides/providing-services/#–-deep-read
entity myEntity: cuid, managed {
field1 : String;
comp : Composition of one myComposition;
}
aspect myComposition: cuid, managed {
myCompField: String;
}
const result = await SELECT.from(myEntity)
.columns(e => {
e('*')
e.comp(c => c.myCompField) //expand composition, but only select 'myCompField'
})
Update 14.09.2023: is now fixed (#)
A Composition of one can be updated via the Parent Entity, like we would do it, when dealing with an Association to one.
entity myEntity: cuid, managed {
field1 : String;
comp : Composition of one myComposition;
}
aspect myComposition: cuid, managed {
myCompField: String;
}
const { myEntity } = srv.entities
const EntityComposition = srv.entities['myEntity.myComposition'] // composition
srv.after('CREATE', EntityComposition , async (comp, req) => {
await UPDATE(myEntity, comp.ID)
.set({
comp : [{ myCompField: 'test' }]
})
})
A Composition of many must be updated via the actual Composition Entity.
entity myEntity: cuid, managed {
field1 : String;
comp : Composition to many myComposition;
}
aspect myComposition: cuid, managed {
myCompField: String;
}
const EntityComposition = srv.entities['myEntity.myComposition'] // composition
srv.after('CREATE', EntityComposition , async (comp, req) => {
await UPDATE(EntityComposition, { up__ID: comp.up__ID, ID: comp.ID }).set({ myCompField: 'test' })
})