# SQL console

> Run scripts with autocompletion, preview writes before they happen, and read query plans as a tree.

Source: https://fleetdock.dev/docs/sql-console


The SQL console runs a script of one or more statements, separated by `;`, in order on one
session. Scripts that write ask for confirmation first, and a running script can be cancelled.
Each user has their own history and saved queries.

The editor sits above the results; drag the separator between them (or focus it and use the
arrow keys) to give either more room. Results appear in the same grid as tables: move with the
keyboard, copy rows as TSV, JSON or `INSERT` statements, resize columns and sort by clicking a
header (sorting happens in the browser, on the rows returned). The row limit next to **Run** sets
how many rows a statement returns: 200, 1,000 or 5,000.

A MySQL-style `DELIMITER` line lets you create procedures and triggers whose bodies contain `;`.

## Autocompletion [#autocompletion]

The editor completes keywords and the database's real tables and columns (on PostgreSQL,
qualified by schema), with each column's type alongside. It completes what the data login can
see.

## Preview before writing [#preview-before-writing]

**Preview** dry-runs a script that writes. It runs the whole script in one transaction that is
always rolled back, and shows:

<Screenshot name="sql-console" />

* how many rows each statement would change;
* for a single-table `UPDATE` or `DELETE`, up to 20 of the affected rows before and after, with
  changed cells highlighted.

Then **Apply for real** runs the script with the usual confirmation, quoting the preview's
numbers.

<Callout type="warn">
  A preview really executes the statements, then rolls them back. Triggers fire, sequence and
  `AUTO_INCREMENT` counters advance, and the affected rows are locked while it runs. Only
  `SELECT`, `INSERT`, `UPDATE`, `DELETE`, `REPLACE` and `MERGE` can be previewed: no DDL,
  transaction control, `SET` or `CALL`. On MySQL and MariaDB, a database with MyISAM, Aria or
  MEMORY tables cannot be previewed, because those changes cannot be rolled back.
</Callout>

## Explain and Analyze [#explain-and-analyze]

* **Explain** shows how the database would run one statement, as a collapsible tree. Each node
  shows its estimated rows and cost, with bars that show where the cost is. Nothing runs.
* **Analyze** runs the statement (reads only) in a read-only transaction that is rolled back, and
  adds the actual rows and time per step.

<Screenshot name="explain-plan" />

Fleetdock flags the usual suspects: full scans of large tables, `Using filesort` /
`Using temporary`, and row estimates off by 10× or more (stale statistics). **Raw** shows the
engine's JSON plan.

See also [Performance](/docs/performance).