Transforms

PRQL queries are a pipeline of transformations (“transforms”), where each transform takes the previous result and adjusts it in some way, before passing it onto to the next transform.

Because PRQL focuses on modularity, we have far fewer transforms than SQL, each one fulfilling a specific purpose. That’s often referred to as “orthogonality”.

These are the currently available transforms:

Transform Purpose SQL Equivalent
from Start from a table FROM
derive Compute new columns SELECT *, … AS …
select Pick & compute columns SELECT … AS …
filter Pick rows based on their values WHERE, HAVING,QUALIFY
sort Order rows based on the values of columns ORDER BY
join Add columns from another table, matching rows based on a condition JOIN
take Pick rows based on their position TOP, LIMIT, OFFSET
group Partition rows into groups and applies a pipeline to each of them GROUP BY, PARTITION BY
aggregate Summarize many rows into one row SELECT foo(…)
window Apply a pipeline to overlapping segments of rows OVER, ROWS, RANGE