prql

# PRQL

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**P**ipelined **R**elational **Q**uery **L**anguage, pronounced "Prequel".

PRQL is a modern language for transforming data — a simple, powerful, pipelined
SQL replacement. Like SQL, it's readable, explicit and declarative. Unlike SQL,
it forms a logical pipeline of transformations, and supports abstractions such
as variables and functions. It can be used with any database that uses SQL,
since it compiles to SQL.

PRQL can be as simple as:

```elm
from tracks
filter artist == "Bob Marley"                 # Each line transforms the previous result
aggregate {                                   # `aggregate` reduces each column to a value
  plays    = sum plays,
  longest  = max length,
  shortest = min length,                      # Trailing commas are allowed
}
```

Here's a larger example of the language:

```elm
from employees
filter start_date > @2021-01-01               # Clear date syntax
derive {                                      # `derive` adds columns / variables
  gross_salary = salary + (tax ?? 0),         # Terse coalesce
  gross_cost = gross_salary + benefits_cost,  # Variables can use other variables
}
filter gross_cost > 0
group {title, country} (                      # `group` runs a pipeline over each group
  aggregate {                                 # `aggregate` reduces each group to a value
    average gross_salary,
    sum_gross_cost = sum gross_cost,          # `=` sets a column name
  }
)
filter sum_gross_cost > 100_000               # `filter` replaces bo