CAST vs TO_DATE: Fixing String Dates

It's **Day 79**, and we're fixing data types. Often, lazy developers store dates as strings (`VARCHAR`) instead of the `DATE` type. This means you can't use `ORDER BY` or find the "Last 30 days."

The Simple Fix: CAST

If the string is already in a standard format (YYYY-MM-DD), use `CAST`.

SELECT CAST(date_string AS DATE) FROM orders;

-- Or Postgres shorthand:

SELECT date_string::DATE FROM orders;

The Complex Fix: TO_DATE

What if the date is formatted like "01-Jan-2024"? `CAST` will fail. You need to tell SQL exactly how to read it.

SELECT TO_DATE(date_string, 'DD-Mon-YYYY') FROM orders;

Why this is critical

Once your column is a "True Date," you unlock all the powerful time-series functions we learned in Phase 2 and 5. You can calculate growth, week-over-week changes, and more!

Your Task for Today

Check your database. Are your dates stored as `DATE`, `TIMESTAMP`, or `VARCHAR`? If they are `VARCHAR`, practice casting them.

*Day 80: Deduplication with DISTINCT ON (Postgres Specialty).*