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MySQL

Test data in MySQL or MySQL-compatible databases (e.g. MariaDB).

1. Install​

uv tool install --python python3.11 --upgrade 'datacontract-cli[mysql]'

See Installation for pip, pipx, and Docker.

2. Authenticate​

Create a .env file in your working directory (or export the variables):

# .env
DATACONTRACT_MYSQL_USERNAME=root
DATACONTRACT_MYSQL_PASSWORD=mysecretpassword

3. Create a contract from your tables​

Import the table metadata directly from the database. This also generates a ready-to-test servers block:

datacontract import mysql \
  --source localhost \
  --database mydb \
  --table orders \
  --output datacontract.yaml

--source is the host of your MySQL server. Add --port if it doesn't listen on the default 3306, repeat --table for multiple tables, or omit it to import every table in the database.

Only have a DDL file? datacontract import sql --source orders.sql --dialect mysql works too, but writes a servers block with placeholder values that you have to fill in by hand.

4. Test the actual data​

datacontract test datacontract.yaml
Testing datacontract.yaml
Server: mysql (type=mysql, host=localhost, port=3306, database=mydb)
╭────────┬─────────────────────────────────────────────────┬─────────────────┬─────────╮
│ Result │ Check                                           │ Field           │ Details │
├────────┼─────────────────────────────────────────────────┼─────────────────┼─────────┤
│ passed │ Check that field 'order_id' is present          │ orders.order_id │         │
│ passed │ Check that field order_id has no missing values │ orders.order_id │         │
│  ...   │                                                 │                 │         │
╰────────┴─────────────────────────────────────────────────┴─────────────────┴─────────╯
🟢 data contract is valid. Run 24 checks. Took 2.1 seconds.

5. Let it catch a violation​

The contract becomes valuable when it detects drift. Tighten an expectation — for example, add a quality rule to a schema in datacontract.yaml:

schema:
  - name: orders
    # ...
    quality:
      - type: sql
        description: No order has a negative total
        query: SELECT COUNT(*) FROM orders WHERE order_total < 0
        mustBe: 0

Run datacontract test datacontract.yaml again: every violation is listed as an error, and the command exits with code 1 — ready for CI/CD and scheduled runs so you catch drift before your consumers do.

Reference​

All authentication options and the data type mappings: MySQL Reference.

Troubleshooting​

  • Access denied for user — check the two environment variables above and the user's host restrictions ('user'@'%' vs 'user'@'localhost').
  • Can't connect to MySQL server — host/port in the servers block are wrong, or the server doesn't accept remote connections (bind-address).