Enum squeal::Term

pub enum Term {
    Atom(String),
    Condition(Box<Term>, Op, Box<Term>),
    Parens(Box<Term>),
    Null,
}

The Term enum is used to specify a condition in a query (WHERE clause). It is used in the Query struct.

A Term can be an atom, a condition, parentheses or null. Observant minds might notice that this is a fragment of a grammar and simply a reified syntax tree.

Examples

Atom:

use squeal::*;
let result = Term::Atom("a".to_string()).sql();
assert_eq!(result, "a");

A number of different conditions and complex combinations:

use squeal::*;
let result = Term::Condition(
   Box::new(Term::Atom("a".to_string())),
  Op::O("<>".to_string()),
Box::new(Term::Atom("b".to_string())),
).sql();
assert_eq!(result, "a <> b");

An example setting up a = b AND (c = d OR e <> f):

use squeal::*;
let result = Term::Condition(
  Box::new(Term::Atom("a".to_string())),
Op::Equals,
Box::new(Term::Condition(
  Box::new(Term::Atom("b".to_string())),
Op::And,
Box::new(Term::Parens(Box::new(Term::Condition(
 Box::new(Term::Atom("c".to_string())),
Op::Equals,
Box::new(Term::Condition(
Box::new(Term::Atom("d".to_string())),
Op::Or,
Box::new(Term::Atom("e".to_string())),
))))))))).sql();
assert_eq!(result, "a = b AND (c = d OR e)");

Variants

Atom(String)

An atom is a single identifier.

Condition(Box<Term>, Op, Box<Term>)

A condition is a combination of two terms and an operator.

Parens(Box<Term>)

A parenthesized term.

Null

A null term.

Trait Implementations

impl Sql for Term

fn sql(&self) -> String