> ## Documentation Index
> Fetch the complete documentation index at: https://docs.helix-db.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Branch, repeat, and condition queries
> Compose sub-traversals and gate named entries without leaving one transaction
Guide
`sub()` starts an inline traversal that consumes the current stream. Use it for
branching operations; use `g()` only for a top-level traversal entry.
## Branching operations
| Operation | Behavior |
| ------------------------------- | -------------------------------------------- |
| `optional(sub)` | Keep the input when the branch has no result |
| `union(subs)` | Concatenate results from every branch |
| `choose(predicate, then, else)` | Select one branch |
| `coalesce(subs)` | Use the first non-empty branch |
| `repeat(sub, config)` | Apply a traversal with an explicit bound |
## Retain row-local values
Bind the starting service, use `optional` and `union` sub-traversals to bind each
candidate workload path, then use `projectDistinctBindings` with `coalesce` to produce
one stable row shape. See [projections](/database/helix-db/query-guides/projections#project-correlated-bindings).
## Gate later entries
Batch conditions refer to earlier entry results:
Create the `user` entry, then add `posts` with `varAsIf` / `var_as_if` and a
`varNotEmpty("user")` condition. Conditions serialize inside the named entry, not as
a separate step.
## Bound recursive work
Recursive and fan-out operations must have application-level bounds. Prefer explicit
depth, candidate, and response limits. A response `limit` does not necessarily bound
all work performed before that operation.
## Next steps
Emit stable rows from correlated paths.
Bind values and bounds at request time.