# Explore your warehouse

> Browse schemas, tables, views and columns, and preview real rows, without writing any SQL.

The Explorer shows what is actually in your warehouse, read live from its own catalogue: these schemas, these tables and views, these columns, these rows. Other pages show a reading of the warehouse (the semantic map shows the tables someone put on it, the capacity card shows a byte count). The Explorer is the one that answers "what is in there?" the way a database console does.

It is read-only. Nothing you do here changes your data. Changes are made in [Modelling](https://docs.sanda-os.com.au/modelling) or the [SQL shell](https://docs.sanda-os.com.au/warehouse/sql), and the Explorer links to both.

## Open the Explorer

Go to **Data · Explorer**. You can also press **Explore** in the header of the **Warehouse** page, or **Explore** on a warehouse's card to open that warehouse's tree. Every member of the workspace can use it.

![The Explorer with the mapping schema open and the columns of a table shown](https://docs.sanda-os.com.au/media/explorer-columns.png "The tree on the left, the selected table on the right")

## Read the tree

The tree on the left has four levels: the warehouse (the database), a schema, a folder, then the object.

- **Warehouses.** Every warehouse in your workspace is a root in the same tree, your own first and the sanda sample dataset last, tagged **sample**. A warehouse that is not `healthy` shows its status instead.
- **Schemas.** `raw`, `derived`, `mapping`, `search` and `meta`, each with the number of objects in it. See [sanda warehouse](https://docs.sanda-os.com.au/warehouse) for what each one holds.
- **Folders.** **Tables**, **Views**, **Materialized views** and **Procedures**. Every schema shows **Tables** and **Views**. `derived` always shows all four, because it is the one you build in. Other schemas show **Materialized views** and **Procedures** only when they hold something.
- **Objects.** Tables and materialized views show an approximate row count on the right, so you can see where the data is without opening anything. A small **!** means the object's last build failed. A layers icon means the object is on the semantic fluid.

Use the search box, **Find a table, view or procedure**, to filter by name. Search opens every branch that matches, but it only searches warehouses whose tree you have already opened, so open a warehouse first.

## The warehouse summary

Select a warehouse to see its summary:

| Fact | What it tells you |
|---|---|
| **Storage** | The size of the whole database, and when it was last measured. |
| **Tables** | How many tables there are across every schema. |
| **Views** | How many views and materialized views there are. |
| **On the map** | How many relations the semantic fluid may query. |

Below the facts, a table lists each schema with its number of tables, views, materialized views and procedures, its estimated rows and its size. Row counts are the database's own estimates, and sizes include indexes. A table nobody has counted yet shows no count in the tree, and **not counted yet** in its header.

The summary also says how much of `derived` you have modelled, and links to **Modelling** and **SQL shell**.

## Inspect a table or view

Select an object to open it. The header shows its kind, and, where they apply:

- its version, for anything sanda defined in `derived`;
- **last build failed**, if a materialized view's most recent build did not finish;
- **on the map**, with a link to the semantic fluid, and the name it has there;
- **not readable by sanda**, if the modelling login cannot select from it, which can happen to a table created some other way. Its columns are still listed.

Under that, a line of facts: rows (`about 12.5K`), size, number of columns, the primary key, and what a view reads. A view holds no rows of its own, so it shows **as many as it reads**. A materialized view shows when it was last built and how long the build took.

### Columns

The **Columns** tab lists each column in the table's own order: its position, name, type, whether it allows nulls, and its default. A key icon marks a primary key column, because the key is the grain of the table. A lock marks a column whose values the preview will not show (see below).

### Data preview

The **Data preview** tab reads the first rows of the table when you open it, and again when you press **Refresh**. A preview shows:

- up to 50 rows and the first 60 columns (the **Columns** tab lists the rest);
- no particular order. The preview asks for rows without sorting so that a huge table answers at once, so it is a look at the shape of the data, not a report;
- long values cut at 300 characters.

A preview is a real query on your warehouse, run inside a read-only transaction. It happens when you open the tab, not when you click a table to read its columns.

### Definition

For a view, a materialized view or a procedure, the **Definition** tab shows the SQL it is, and what it reads. A view runs its statement over what it reads each time it is asked. A materialized view holds the rows its statement produced when it was last built.

### History

Anything sanda defined in `derived` has a **History** tab, with the same content as in Modelling:

- **Runs**: each build or call, when it ran, what started it, the outcome, how long it ran, what it was billed as, and the rows and size afterwards.
- **Definitions**: every version, what changed and who asked, with the statement sanda ran.
- **Activity**: the audit records for the object.

An object in `derived` that was made some other way, for example by a table created in the [SQL shell](https://docs.sanda-os.com.au/warehouse/sql), is listed but has no history. The pane says **Made outside sanda**, and sanda will not drop it for you.

## What the Explorer hides

Two kinds of column are counted but never listed or fetched:

- **Bookkeeping columns.** The managed sync and the CSV loader add columns of their own to landing tables, whose names start with an underscore and a reserved prefix. The Explorer leaves them out everywhere, and the header says how many were not shown, for example **2 of the loader's own not shown**. See [SQL reference](https://docs.sanda-os.com.au/reference/sql) for what they hold.
- **Columns whose names look like secrets.** A name with a word like `password`, `token`, `secret` or `api_key` in it is listed with a lock, and its values are withheld from previews. The **Data preview** tab says how many columns were withheld.

The Explorer also does not list the managed sync's own working area, which is not yours to read.

## Row counts are estimates

The number next to each object, and on the summary, comes from the database's statistics, not from counting the rows. It is quick, and it can be a little behind after a large sync. If you need an exact figure, run `select count(*)` in the [SQL shell](https://docs.sanda-os.com.au/warehouse/sql).

## Where to make changes

| To do this | Go to |
|---|---|
| Draw, write or redefine a view, or schedule a rebuild | [Modelling](https://docs.sanda-os.com.au/modelling) |
| Run your own statement, read-only or read-write | [sanda sql](https://docs.sanda-os.com.au/warehouse/sql) |
| See or change storage and compute limits | The **Warehouse** page: **Capacity and limits** takes you there |
| Put a table on the semantic fluid | [The semantic fluid](https://docs.sanda-os.com.au/semantic-fluid) |

:::links
- [sanda sql](https://docs.sanda-os.com.au/warehouse/sql): Run your own SQL when browsing is not enough.
- [Views and modelled tables](https://docs.sanda-os.com.au/modelling/views): Turn what you find here into something the fluid can use.
- [SQL reference](https://docs.sanda-os.com.au/reference/sql): Schemas, naming and the columns sanda adds.
:::