Struct WhereCondition 

pub struct WhereCondition<'a> { /* private fields */ }

A structure to hold the where condition of the queries. It is designed to be a composable structure to build the where condition of the queries alongside the according parameters, preserving the order of the parameters. The conditions are composed using the and_where and or_where methods with a default representation of true if no condition is provided.

Examples

Default condition

The default condition is true which is useful when the conditions are passed as parameters. This way, when no condition is provided, the query will be like select * from table where true. The condition will be ignored by the database planner and will return all the records.

use agrum::{WhereCondition, params};

let condition = WhereCondition::default();
assert_eq!("true", condition.to_string());

Building a condition

The WhereCondition structure can be built using the new method to create a new condition with a SQL expression and the parameters. The and_where and or_where methods can be used to compose the conditions with the boolean logic operators. The expand method can be used to get the SQL expression and the parameters (consuming the instance).

use agrum::{WhereCondition, params};

let condition = WhereCondition::new("A = $?", params![1_i32]);
let condition = condition.and_where(WhereCondition::new("B = $?", params![2_i32]));
let condition = condition.or_where(WhereCondition::new("C = $?", params![3_i32]));
assert_eq!("A = $? and B = $? or C = $?", condition.to_string());

Implementations

impl<'a> WhereCondition<'a>

pub fn new(expression: &str, parameters: Vec<&'a dyn ToSqlAny>) -> Self

Create a new condition with a SQL expression and the parameters.

pub fn expand(self) -> (String, Vec<&'a dyn ToSqlAny>)

Expand the condition to a SQL expression and the parameters (consuming the instance). This is normally used to get the SQL expression and the parameters.

pub fn where_in(field: &str, parameters: Vec<&'a dyn ToSqlAny>) -> Self

Create a new condition with a IN SQL expression and the parameters. It creates as many $? placeholders as the number of parameters.

pub fn and_where(self, condition: WhereCondition<'a>) -> Self

Compose the condition with a AND boolean logic operator.

pub fn or_where(self, condition: WhereCondition<'a>) -> Self

Compose the condition with a OR boolean logic operator.

Trait Implementations

impl<'a> Clone for WhereCondition<'a>

fn clone(&self) -> WhereCondition<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for WhereCondition<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Default for WhereCondition<'a>

fn default() -> Self

Returns the “default value” for a type.

impl Display for WhereCondition<'_>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.