Error Reference

All errors are sentinel values. Test them with errors.Is. Errors from deeper layers wrap these, so errors.Is keeps working through wrapped chains.

_, err := conn.Update("users").Set("active", false).Exec(ctx)
if errors.Is(err, db.ErrNoWhere) {
    // forgot a WHERE clause
}

Builder errors are collected while you chain and returned by the terminal call. Err() (on every builder) shows the first one early. See Core Concepts.

Error	Returned when	Typical fix
db.ErrNotFound	First, Find, Sole or Value matched no row. It is sql.ErrNoRows	Handle "not found" explicitly
db.ErrMultipleRecords	Sole matched more than one row	Add a filter, or use First
db.ErrNoOrder	Chunk was called without an ORDER BY	Add OrderBy, or use ChunkByID
db.ErrNotBound	A query ran on a DB with no connection (db.Use)	Use db.New(conn, dialect)
db.ErrNoTransaction	Transaction on a connection that cannot begin one	Pass a *sql.DB (or a connection that supports BeginTx)
db.ErrUnknownDialect	The dialect value is not a known one	Use a db.Postgres, db.MySQL, db.MariaDB or db.SQLite constant
db.ErrInvalidOperator	An operator outside the allow-list	See allowed operators
db.ErrInvalidDirection	An order direction other than asc or desc	Fix the direction
db.ErrNoTable	The query has no table	Call From (or FromSub, FromRaw)
db.ErrInvalidArgs	Arguments the library cannot use: wrong argument count, a non-struct passed to a struct write, an unsafe index name, a missing TableName(), a malformed cursor, mismatched insert rows, ...	Read the wrapped message for the detail
db.ErrUnsupported	The feature does not exist on this dialect (RETURNING on MySQL, lateral joins on SQLite, ...)	See Dialect Differences
db.ErrJoinNeedsOn	A join (other than a cross join) has no ON condition	Add the join condition
db.ErrNoValues	A write had nothing to write (insert with no rows, update with nothing to set, all fields omitted)	Check omitempty fields and empty inputs
db.ErrNoWhere	An update or delete (including Increment*) has no WHERE or LIMIT and no AllRows()	Add a filter, or call AllRows() on purpose

Handling patterns

var u User
err := conn.Select().From("users").Find(ctx, id, &u)
switch {
case err == nil:
    // found
case errors.Is(err, db.ErrNotFound):
    // 404
default:
    // 500: log it. Driver errors can echo values, treat as sensitive
}

Database driver errors (constraint violations, connection failures) are not quill sentinels. They pass through from your driver, so use the driver's own error types (for example, a unique-violation code) to detect them.