One post tagged with "window functions"

Window functions and Common Table Expressions (CTEs) are now generally available in StackQL. These features work with both the embedded SQLite backend and PostgreSQL backend.

Window Functions​

Window functions allow you to perform calculations across sets of rows related to the current row. Supported functions include:

• Ranking: ROW_NUMBER(), RANK(), DENSE_RANK(), NTILE()
• Offset: LAG(), LEAD(), FIRST_VALUE(), LAST_VALUE(), NTH_VALUE()
• Distribution: PERCENT_RANK(), CUME_DIST()
• Aggregates as window functions: SUM(), COUNT(), AVG(), etc. with OVER clause

Example: Ranking Contributors​

SELECT
    login,
    contributions,
    DENSE_RANK() OVER (ORDER BY contributions DESC) as rank
FROM github.repos.contributors
WHERE owner = 'stackql' AND repo = 'stackql';

Example: Running Totals​

SELECT
    login,
    contributions,
    SUM(contributions) OVER (ORDER BY contributions DESC) as running_total,
    ROUND(100.0 * contributions / SUM(contributions) OVER (), 2) as pct_of_total
FROM github.repos.contributors
WHERE owner = 'stackql' AND repo = 'stackql';

Common Table Expressions (CTEs)​

CTEs let you define temporary named result sets using the WITH clause. This simplifies complex queries by breaking them into logical components.

Example: Aggregating Across Multiple Resources​

WITH all_contributors AS (
    SELECT login, contributions
    FROM github.repos.contributors
    WHERE owner = 'stackql' AND repo = 'stackql'
    UNION ALL
    SELECT login, contributions
    FROM github.repos.contributors
    WHERE owner = 'stackql' AND repo = 'stackql-deploy'
)
SELECT
    DENSE_RANK() OVER (ORDER BY SUM(contributions) DESC) as rank,
    login,
    SUM(contributions) as total_contributions
FROM all_contributors
GROUP BY login
ORDER BY total_contributions DESC;

Documentation​

Full documentation is available:

• Window Functions
• WITH (CTEs)
• SELECT

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