Merge pull request 'coalesce' (#21) from dev into main

Reviewed-on: #21

src/defaultHandler.ts

@@ -825,7 +825,25 @@ export class Handler {
             }
             builder.addCode(")");
             return builder;
-        }
+        },
+        coalesce: (handler: Handler, a: allModifierInput[]): QueryBuilder => {
+            const builder = new QueryBuilder();
+            builder.addCode("COALESCE(");
+            for (let i = 0; i < a.length; i++) {
+                const e = a[i];
+                if (e instanceof Attribute || e instanceof AttributeAlias) builder.addCode(e.getString());
+                else if (e instanceof Alias)
+                    builder.addCode(handler.builders.escapeID(e.toString()));
+                else if (e instanceof Modifier || e instanceof selectQuery || e instanceof Aggregation) {
+                    builder.append(e.serialize(handler));
+                } else {
+                    builder.addInjection(e);
+                }
+                if (i < a.length - 1) builder.addCode(", ");
+            }
+            builder.addCode(")");
+            return builder;
+        },
     }
 
     datatypes = {

src/funcs.ts

@@ -24,6 +24,7 @@ export const regexp = (a: allModifierInput, b: allModifierInput) => new BooleanM
 export const exists = (q: selectQuery) => new BooleanModifier("exists", [q]);
 
 export const concat = (...args: allModifierInput[]) => new StringModifier("concat", args);
+export const coalesce = (...args: allModifierInput[]) => new StringModifier("coalesce", args);
 
 //aggregations
 export const count = (a: Attribute) => new Aggregation("count", a);