sqldq

SQLDQ

SQLDQ is a Data Quality Testing library that keeps it simple and flexible.

Simply use SQL to define your checks.

Support

You can run data quality checks on:

Installation

pip install sqldq / uv pip install sqldq

You also need to install the corresponding libraries for your backend of choice, .e.g. duckdb when using .from_duckdb. sqldq`s error messages will also inform you about missing dependencies.

Examples

To see all of its features and examples for all supported backends, see the demo folder.

The basic workflow is as follows:

from sqldq import SQLDQ
import duckdb
import polars as pl

# Sample data
df_users = pl.DataFrame({
    "user_id": [1, 2, 2],          # Duplicate user_id=2
    "age": [25, 150, 45],          # Age 150 is an unplausible outlier
    "email": ["user1@example.com",
              "user2@example.com",
              "invalid-email"],    # Invalid email
})

# Connect via DuckDB
con = duckdb.connect()
con.register("users", df_users)

dq = SQLDQ.from_duckdb(connection=con)

# Define DQ checks
dq = (
    dq.add_check(
        name="check_duplicate_user_id",
        failure_rows_query="""
            WITH duplicate_users AS (
                SELECT user_id, COUNT(*) AS count
                FROM users
                GROUP BY user_id
            )
                SELECT user_id
                FROM duplicate_users
                WHERE count > 1""")
    .add_check(
        name="check_invalid_email",
        failure_rows_query="""
            SELECT user_id
            FROM users
            WHERE email NOT LIKE '%_@__%.__%'
        """)
    .add_check(
        name="check_age_outlier",
        failure_rows_query="""
            SELECT user_id, age
            FROM users
            WHERE age NOT BETWEEN 0 AND 120"""))

# Run checks
result = dq.execute()

# Report on results
report = result.report(include_rows=True,
                       include_summary_header=True,
                       fail_only=True)
print(report)

# Control flow
if result.has_failures():
    print("Checks failed. here we can take custom actions.")

Development

# open devcontainer
uv sync
source .venv/bin/activate
make check
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