Predicates & Expressions topic

Expressions

An Expression wraps a typed AST node representing a SQL predicate or value expression. Columns produce them via comparison methods and operator sugar.

Predicates

All return Expression<bool, Tbl>:

Method	SQL
col.eq(v) / col.ne(v)	= ? / <> ?
col.gt/ge/lt/le(v)	> ? / >= ? / < ? / <= ?
col > v, col < v, col >= v, col <= v	operator sugar for the above
col.isIn([...])	IN (?, ?, …)
col.between(lo, hi)	BETWEEN ? AND ?
col.isNull() / col.isNotNull()	IS NULL / IS NOT NULL
col.like('%a%')	LIKE ? (text columns only)
a.eqColumn(b)	a = b (column-to-column; shared key type enforced)

Combine predicates with & (AND) / | (OR), or .and() / .or():

from(Users.table).where((Users.age > 28) & Users.active.eq(1));

Gotcha: chained .where(a).where(b) replaces the predicate (last wins) — use a single .where(...) with &/|, or use .filter(...), which ANDs repeated calls (filter(a).filter(b) ⇒ WHERE a AND b).

Scoping

Every Expression<T, Tbl> is scoped to a table type Tbl. A single-table query (from(Users.table)) is a Query<Users>, so only Users columns type-check in .where(...). After a join the scope relaxes to Query<Object?>, and QueryBuilder validates at build time that every referenced table is present in the FROM/JOIN clauses — see Serialization.

Raw SQL fragments

For expressions the builder doesn't model, rawCondition(sql) is a boolean fragment for having (or a joined where/filter). Use ? placeholders + params:

from(Users.table).having(rawCondition('count(*) > ?', params: [10]));

For typed selections in the projection, see raw<T>(...) in Schema.

Classes

Expression<T, Tbl>

A typed SQL expression.