wip: attach cardinality to join nodes

db-service/lib/cqn4sql.js

@@ -313,7 +313,11 @@ function cqn4sql(originalQuery, model) {
           lhs = joinForBranch(lhs, c)
         })
       }
-      return lhs.args.length > 1 ? lhs : lhs.args[0]
+      const res = lhs.args.length > 1 ? lhs : lhs.args[0]
+      // default is to-one
+      if(nextAssoc && nextAssoc.$refLink.definition)
+        Object.defineProperty(res, 'element', { value: nextAssoc.$refLink.definition, /* why do we need this */writable: true })
+      return res
     }
   }
 

db-service/test/cqn4sql/assocs2joins.test.js

@@ -22,6 +22,15 @@ describe('Unfolding Association Path Expressions to Joins', () => {
       `
     expect(query).to.deep.equal(expected)
   })
+  it('in select, one assoc to many', () => {
+    let query = cqn4sql(CQL`SELECT from bookshop.Authors { ID, name } where books.title LIKE '%Potter%'`, model)
+    const expected = CQL`SELECT from bookshop.Authors as Authors
+        left outer join bookshop.Books as books on books.author_ID = Authors.ID
+        { Authors.ID, Authors.name }
+        where books.title LIKE '%Potter%'
+      `
+    expect(query).to.deep.equal(expected)
+  })
 
   it('in select, one deep assoc, with filter', () => {
     let query = cqn4sql(CQL`SELECT from bookshop.Books { ID, dedication.addressee[name = 'Hasso'].name }`, model)

hana/lib/HANAService.js

@@ -686,6 +686,17 @@ class HANAService extends SQLService {
       return sql
     }
 
+    from(from, q) {
+      const { element, ref, SELECT } = from
+      if (!element?.cardinality || ref || SELECT) return super.from(from, q)
+      const { type, cardinality: { min, max } } = element
+      const cardinality =
+        (type === 'cds.Composition' ? 'EXACT ONE' : 'MANY')
+        + ' TO '
+        + (max == 1 ? min == 1 ? 'EXACT ONE' : 'ONE' : 'MANY')
+      if (from.join) return `${this.from(from.args[0])} ${from.join} ${cardinality} JOIN ${this.from(from.args[1])}${from.on ? ` ON ${this.where(from.on)}` : ''}`
+    }
+
     from_dummy() {
       return ' FROM DUMMY'
     }