Lesson 17.1

SQL Playground Mission: Map a Dataset Before Querying

Start freeform SQL work by building a quick map of table sizes.

Before writing a report on an unfamiliar dataset, map the tables. A row-count inventory tells you which tables are small lookup tables, which tables hold transactional detail, and where a join might multiply rows.

This mission uses UNION ALL to stack one small count query per table. It is the same habit you can use in the playground before exploring your own CSV or Parquet upload.

Pattern

select 'first_table' as table_name, count(*) as rows from first_table
union all
select 'second_table', count(*) from second_table
order by rows desc, table_name

Schema · Garden ShopView dataset schema6 tables

Table · customers

One row per customer. Some customers have no phone on file.

9 columns · 20 rows

customer_id intfirst_name textlast_name textemail textphone textcity textstate textsignup_date dateis_active bool

Table · products

One row per product, with price, cost, and inventory levels.

9 columns · 24 rows

product_id intproduct_name textcategory_id intsupplier_id intprice decimalcost decimalquantity_on_hand intreorder_level intdiscontinued bool

Table · categories

Lookup table of product categories.

2 columns · 8 rows

category_id intcategory_name text

Table · orders

One row per order. Unshipped orders have a null shipped_date.

6 columns · 24 rows

order_id intcustomer_id intorder_date dateshipped_date datestatus textcoupon_code text

Table · order_items

One row per line item within an order.

5 columns · 48 rows

order_item_id intorder_id intproduct_id intquantity intunit_price decimal

Table · suppliers

One row per supplier. Some suppliers have no contact email.

4 columns · 6 rows

supplier_id intsupplier_name textcontact_email textstate text

Your task

Return a table inventory for Garden Shop. The result should havetable_name and rows, covering customers, products, categories, orders, order_items, and suppliers. Sort by row count descending, then table name.

SQL Workbench

query.sqlgarden_shop · SQL engine loading

⌘↵ to run

Expected answer