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SQLite statistical functions

⚠️ This extension is deprecated. Use sqlean-stats instead.

This library provides common statistical functions for SQLite. Adapted from extension-functions.c by Liam Healy.

Provides following functions:

  • mode - mode,
  • median - median (50th percentile),
  • percentile_25 - 25th percentile,
  • percentile_75 - 75th percentile,
  • percentile_90 - 90th percentile,
  • percentile_95 - 95th percentile,
  • percentile_99 - 99th percentile,
  • stddev or stddev_samp - sample standard deviation,
  • stddev_pop - population standard deviation,
  • variance or var_samp - sample variance,
  • var_pop - population variance.

SQLite CLI usage

Use .load command:

sqlite> .load dist/sqlite3-stats.so;

Then use library functions:

with tbl as (
    select value from generate_series(1, 99, 1)
)

select 'count' as metric, count(value) as value
from tbl
union all

select 'median' as metric, median(value)
from tbl
union all

select 'percentile_25' as metric, percentile_25(value)
from tbl
union all

select 'percentile_75' as metric, percentile_75(value)
from tbl
union all

select 'percentile_90' as metric, percentile_90(value)
from tbl
union all

select 'percentile_95' as metric, percentile_95(value)
from tbl;
┌───────────────┬───────┐
│    metric     │ value │
├───────────────┼───────┤
│ count         │ 99    │
│ median        │ 50    │
│ percentile_25 │ 25    │
│ percentile_75 │ 75    │
│ percentile_90 │ 90    │
│ percentile_95 │ 95    │
└───────────────┴───────┘

In-app usage

Typically there are two necessary actions:

  1. Enable extension loading.
  2. Load specific extension.

See your SQLite driver / library documentation for details.

For example, in Python:

import sqlite3

connection = sqlite3.connect(":memory:")
connection.enable_load_extension(True)
connection.load_extension("./sqlite3-stats.so")
connection.execute("select median(1)")
connection.close()

Building from source

Linux:

gcc -fPIC -lm -shared src/stats.c -o dist/sqlite3-stats.so

Mac OS X:

gcc -fno-common -dynamiclib src/stats.c -o dist/sqlite3-stats.dylib

Windows:

gcc -shared -I ./src src/stats.c -o dist/sqlite3-stats.dll