Module sql 

Traits that classify SQL type markers, so query builders can check operations at compile time.

Every expression carries a SQL type marker, a zero-sized type such as postgres::types::Int4 or sqlite::types::Text. The traits here say what a marker can do:

Trait	Question it answers	Used for
DataType	Is this a SQL type marker?	every typed expression
Compatible	Can these two types be compared?	eq, lt, IN, LIKE, …
Assignable	Can a value of this type be stored in that column?	bind values, INSERT ... SELECT
Numeric	Is it a number?	+ - * /, SUM, AVG, ABS
Integral	Is it an integer?	LIMIT/OFFSET, SUBSTR positions
Floating	Is it a floating-point number?	dialect type aliases
Textual	Is it a string?	LIKE, UPPER, LENGTH, ILIKE, regex
Binary	Is it raw bytes?	dialect type aliases
Temporal	Is it a date, time or timestamp?	date/time functions
BooleanLike	Can it be a condition?	WHERE, AND/OR/NOT, join ON
ArithmeticOutput / NegOutput	What type does arithmetic produce?	result type of a + b, -a

All traits are implemented by this crate for the dialect markers in sqlite::types, postgres::types and mysql::types. DataType is sealed, so other crates cannot add new markers.

Examples

Generic code can require a capability with a trait bound:

use drizzle_types::{Compatible, Numeric, postgres::types::{Float8, Int4, Text}};

fn comparable<L: Compatible<R>, R: drizzle_types::DataType>() {}
fn numeric<T: Numeric>() {}

comparable::<Int4, Float8>(); // int4 = float8 is allowed
numeric::<Int4>();
// numeric::<Text>(); // error: `Text` is not a numeric SQL type

Structs

Array

SQL array type marker: Array<T> is an array whose elements have SQL type T.

Conjunction

The SQL type of a condition list — a tuple of conditions combined with AND.

Placeholder

SQL type of an untyped placeholder, whose value is bound when the query runs.

Traits

ArithmeticOutput

The SQL type produced by Self <op> Rhs, where both sides are Numeric.

Assignable

SQL types that accept a value of type Rhs: Self is the target (a column or typed placeholder), Rhs the type of the value stored in it.

Binary

Raw byte SQL types.

BooleanLike

SQL types that can be used as a condition: in WHERE, HAVING, join ON, CASE WHEN, and with AND, OR and NOT.

Compatible

SQL types that can be compared with Rhs: Self on the left of =, <, IN, LIKE and similar operators, Rhs on the right.

DataType

A SQL type marker: a zero-sized type that stands for one SQL type.

Floating

Floating-point SQL types.

Integral

Integer SQL types, required where SQL expects a whole number, such as LIMIT/OFFSET and string positions.

NegOutput

The SQL type produced by unary negation, -expr.

Numeric

Numeric SQL types: operands of arithmetic (+, -, *, /, %) and numeric functions such as SUM, AVG, ABS and ROUND.

Temporal

Date and time SQL types: operands of date/time functions.

Textual

String SQL types: operands of LIKE, ILIKE, regex matching and string functions such as UPPER, LOWER, LENGTH and CONCAT.