Practical tools for system, network, security, and operations administrators.

DBA-C0005 · SQL Query Tools

Common Table Expressions (CTEs) Explained

Read one WITH draft and one recursive sketch. Name the stop depth. Do not run either statement.

Updated 25 October 2026 · Explainer

This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.

What this hour is for

The CTE builder drafts a WITH clause from names you type. The recursive tool drafts a hierarchy and expects a depth where the walk stops. Neither page runs SQL.

A recursive sketch without a stop is unfinished. Do not run it during the reading. One statement, on a table you can name.

192.0.2.10, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. example.com is a documentation name. A sample password is replaced. It is not a password you keep.

The change you can finish

Apply nothing while you are writing the note. When the lab window opens, it is one change on the database named in the ticket. Read the draft, then the database, then decide.

Rollback is the backup, the file, or the snapshot you saved first. You do not invent a rollback after the only copy is gone.

  1. Name the table.
  2. Read the WITH draft.
  3. Write the stop depth.
  4. Do not run either statement.
  5. Stop.

Mistakes that outlive the statement

Common Table Expressions (CTEs) Explained goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.

Decisions to write down

One decision for Common Table Expressions (CTEs) Explained: The table is written. The stop depth is written. Nothing was run. And the database is yours.

Checks before you call it done

Confirm this before you call the change done: The table is written. The stop depth is written. The draft was read. Nothing was run. And the database is yours. If one of those fails, stop.

-- A WITH draft is one statement.
-- A recursive sketch names its stop depth.
-- Do not run it during the reading.

Before you leave the database

Common Table Expressions (CTEs) Explained ends when the database in the prompt is the database in the ticket. If it is not, you are on the wrong database. Stop.

The draft stays a draft until a person has read the names in it. A generator does not log into the database. You delete a line that names a host, a database, or an account you did not write down.

192.0.2.10, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. example.com is a documentation name. They belong in the note. They are not values you leave on a database because a draft included them.

prompt-for-this is a reminder that a secret is missing. It is not a password, a key, or a token you save in the ticket or in git. A sample password in a draft is replaced. It is not a password you keep.

One change is the window. If two things move and the result is wrong, you will not know which one did it.

If the same step fails twice, stop for the day. Restore the copy you took first.

A second person reads the database name and the change aloud. If they cannot find them in the ticket, the note is not done.

This page is a planning guide. It is not a vendor manual, not an official standard, and not permission to touch a database you do not administer. You do not disable authentication, a firewall, or TLS to make a check pass.

Tools for this guide

These tools run in the browser on this site. They do not log into your machines.

More in this cluster

The pillar for this page, and the next published pages filed with it.