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Lambda Query Language (LQL)

A functional, pipeline-style DSL that transpiles to SQL. Write database logic once and run it against PostgreSQL, SQLite, or SQL Server.

Users
|> filter(fn(row) => row.Age > 18 and row.Status = 'active')
|> join(Orders, on = Users.Id = Orders.UserId)
|> select(Users.Name, sum(Orders.Total) as TotalSpent)
|> group_by(Users.Id)
|> order_by(TotalSpent desc)

LQL is database platform independent. The same .lql source must produce semantically identical results on every target dialect.

Install

Build-time transpilation (recommended)

dotnet new tool-manifest
dotnet tool install Lql --version ${LQL_VERSION}

Then transpile during the build:

dotnet Lql sqlite   --input GetCustomers.lql --output GetCustomers.generated.sql
dotnet Lql postgres --input GetCustomers.lql --output GetCustomers.generated.sql

Runtime transpilation

Reference one of the library packages to transpile LQL in your application code:

dotnet add package Nimblesite.Lql.SQLite   --version ${NIMBLESITE_VERSION}
dotnet add package Nimblesite.Lql.Postgres --version ${NIMBLESITE_VERSION}
dotnet add package Nimblesite.Lql.SqlServer --version ${NIMBLESITE_VERSION}

Runtime API

using Nimblesite.Lql.Core;
using Nimblesite.Lql.Postgres;
using Nimblesite.Sql.Model;

var lql = """
Customer
|> filter(fn(row) => Customer.Active = true)
|> select(Customer.Id, Customer.Name)
""";

var statement = new LqlStatement(lql);
Result<string, SqlError> result = statement.ToPostgreSql();

var sql = result switch
{
    Result<string, SqlError>.Ok ok => ok.Value,
    Result<string, SqlError>.Error err =>
        throw new InvalidOperationException(err.Value.Message)
};

statement.ToSqlite() and statement.ToSqlServer() are also available from their respective packages.

Projects

Project Description
Nimblesite.Lql.Core Core transpiler library and AST
Lql Unified CLI transpiler tool (subcommands: postgres, sqlite)
Nimblesite.Lql.Postgres ToPostgreSql() extension
Nimblesite.Lql.SQLite ToSqlite() extension
Nimblesite.Lql.SqlServer ToSqlServer() extension
LqlExtension VS Code extension (TypeScript)
lql-lsp-rust Language server (Rust, ANTLR-generated parser)
Nimblesite.Lql.TypeProvider.FSharp F# type provider for compile-time validation

Pipeline operators

Operator Purpose
filter(fn(row) => ...) WHERE
select(col1, col2, ...) SELECT projection
join(Table, on = ...) INNER JOIN (plus left_join, right_join, full_join)
group_by(col) GROUP BY
`order_by(col [asc desc])`
limit(n) LIMIT / TOP
distinct() DISTINCT

Aggregates include count, sum, avg, min, max. Parameters are declared with @name.

Related documentation