Macro sql_filter 

sql_filter!() { /* proc-macro */ }

Creates a type-safe SQL filter struct with builder methods using SQL-like syntax.

This macro generates a struct that implements the SqlFilter trait, making it suitable for use with repository query methods that accept SQL filters.

Syntax

sql_filter! {
    [attributes]
    visibility struct StructName {
        SELECT columns FROM table_name WHERE
        condition [AND|OR] condition ...
    }
}

Columns

You can select all columns with * or specify individual columns:

• SELECT * FROM ...: Select all columns
• SELECT col1, col2 as alias FROM ...: Select specific columns with optional aliases

Conditions

Conditions use SQL-like syntax:

[?]column_name [as field_name] OPERATOR type

• Optional ? prefix marks the field as optional in the filter
• column_name is the database column name
• Optional as field_name to use a different field name in the generated struct
• OPERATOR is one of: =, !=, >, <, >=, <=, LIKE, ILIKE, IN, NOT IN
• type is either a Rust type (e.g., i32, String) or a raw SQL string literal

Conditions can be combined with logical operators AND, OR, and NOT.

Generated Code

The macro generates:

1. A struct with fields for each condition
2. A constructor method for required fields
3. Builder methods for optional fields
4. Implementation of the SqlFilter trait

Examples

Basic Filter

sql_filter! {
    pub struct UserFilter {
        SELECT * FROM users WHERE
        id = i32
    }
}

// Usage:
let filter = UserFilter::new(1);

Filter with Optional Fields

sql_filter! {
    pub struct UserFilter {
        SELECT * FROM users WHERE
        ?name LIKE String AND
        ?age >= i32
    }
}

// Usage:
let filter = UserFilter::new()
    .name("John%")
    .age(18);

Filter with Raw SQL

sql_filter! {
    pub struct UserFilter {
        SELECT * FROM users WHERE
        created_at > "NOW() - INTERVAL '1 day'"
    }
}

Complex Filter

sql_filter! {
    pub struct OrderFilter {
        SELECT id, total, name as customer_name FROM orders WHERE
        id = i32 OR
        (total > f64 AND ?customer_id = i32)
    }
}