Skip to content

docs: state varchar/char defaults to '' as a rule, not a preference #271

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
dimitri-yatsenko wants to merge 2 commits into
base: main
Choose a base branch
from
Open

docs: state varchar/char defaults to '' as a rule, not a preference #271

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
34d78fd
docs: state varchar/char defaults to '' as a rule, not a preference
dimitri-yatsenko Sep 3, 2026
6da0f62
docs: extend the empty-string-default rule to enum attributes
dimitri-yatsenko Sep 3, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
14 changes: 12 additions & 2 deletions src/reference/definition-syntax.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -86,14 +86,24 @@ raw_path : <filepath@raw> # Portable file reference
status = "pending" : varchar(20) # String default
count = 0 : int32 # Numeric default
notes = '' : varchar(1000) # Empty string default (preferred for strings)
stage = '' : enum('', 'draft', 'reviewed', 'released') # Empty-string member (preferred for enums)
created = CURRENT_TIMESTAMP : datetime # Auto-timestamp
ratio = NULL : float64 # Nullable (only NULL can be default)
```

**Nullable attributes:** An attribute is nullable if and only if its default is `NULL`.
DataJoint does not allow other defaults for nullable attributes—this prevents ambiguity
about whether an attribute is optional. For strings, prefer empty string `''` as the
default rather than `NULL`.
about whether an attribute is optional.

**`varchar`, `char`, and `enum` attributes should default to `''`, not `NULL`.** `NULL`
and `''` both read as "nothing," and once an attribute allows both, every query and every
`make()` body has to handle two representations of the same absence. For `enum`, this
means adding `''` as an explicit member rather than making the attribute nullable—the
empty string is then just another value the type already enumerates, not a second
absence-mechanism layered on top of it. Reserve `NULL` for an attribute that is
genuinely optional and where "not yet known" must be distinguishable from "known to be
empty"—a case that arises rarely for text, and rarer still for a closed set of values a
schema author chose in the first place.

## Comments

Expand Down
Loading