Local SQL

Playground

Explore the training datasets without affecting graded progress.

Visible safety policyNo mastery effect

Playground runs only SELECT or EXPLAIN SELECT statements against the visible seed, supports reset-to-seed, and does not write mastery, attempts, progress, or review evidence. It is not a full database administration IDE. Scratch queries use the playgroundQueries repository and raw history uses queryHistory:playground; hidden seed rows and expected answers are never stored.

Engine cold Active scratch: Starter product scan.

Unchanged since last Run/CheckPlayground has no mastery effect

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Dataset

Starter Store

Small hand-auditable retail tables for first queries and early retrieval.

Business glossary

Starter Store: Small hand-auditable retail tables for first queries and early retrieval.
customers: one row per customer account
customers.customer_id: Primary identifier for customers.
order_items: one row per product line on an order
order_items.order_item_id: Primary identifier for order_items.
orders: one row per submitted order
orders.order_id: Primary identifier for orders.
products: one row per sellable product
products.product_id: Primary identifier for products.
staff: one row per staff member
staff.staff_id: Primary identifier for staff.

Hidden validation data differs from the visible sample. Use grains, keys, nullability, and relationship cardinality instead of memorizing these rows.

customers5 visible rows

Grain

one row per customer account

Columns

customer_idintegerNot nullKeyUniqueIndexed
Stable customer key.
Default: noneGenerated: no
customer_nametextNot null
Customer display name.
Default: noneGenerated: no
Enumerated values:Avery StoneCasey QuinnJordan LeeMorgan Park
citytextNot null
Customer city.
Default: noneGenerated: no
Enumerated values:AustinChicagoDenverSeattle
loyalty_tiertextNullable
Optional loyalty tier.
Default: noneGenerated: no
Enumerated values:goldsilverNULL
created_atdateNot null
Column from the visible SQL schema.
Default: noneGenerated: no

Relationships

orders.customer_id may contain many rows for one customers row through customers.customer_id.

Fan-out note: joining child rows into customers can multiply the parent grain unless you aggregate or filter at the intended relationship level.

Sample rows

customers visible sample rows
customer_id	customer_name	city	loyalty_tier	created_at
1	Avery Stone	Austin	gold	2025-12-01T00:00:00.000Z
2	Jordan Lee	Chicago	NULL	2026-01-03T00:00:00.000Z
3	Casey Quinn	Austin	silver	2026-01-04T00:00:00.000Z
4	Morgan Park	Seattle	gold	2026-01-09T00:00:00.000Z
5	Jordan Lee	Denver	NULL	2026-01-10T00:00:00.000Z

order_items5 visible rows

Grain

one row per product line on an order

Columns

order_item_idintegerNot nullKeyUniqueIndexed
Line item key.
Default: noneGenerated: no
order_idintegerNullableForeign key
Parent order.
Default: noneGenerated: no
product_idintegerNullableForeign key
Purchased product.
Default: noneGenerated: no
quantityintegerNot null
Units purchased.
Default: noneGenerated: no
unit_pricenumericNot null
Column from the visible SQL schema.
Default: noneGenerated: no

Relationships

order_items.order_id can repeat across many visible rows and references one orders.order_id value.
order_items.product_id can repeat across many visible rows and references one products.product_id value.

Sample rows

order_items visible sample rows
order_item_id	order_id	product_id	quantity	unit_price
1000	100	1	2	6.50
1001	100	2	1	14.00
1002	101	3	4	4.25
1003	102	1	1	6.50
1004	103	4	1	28.00

orders4 visible rows

Grain

one row per submitted order

Columns

order_idintegerNot nullKeyUniqueIndexed
Stable order key.
Default: noneGenerated: no
customer_idintegerNullableForeign key
Customer that placed the order.
Default: noneGenerated: no
staff_idintegerNullableForeign key
Staff member handling the order.
Default: noneGenerated: no
ordered_attimestamp without time zoneNot null
Order timestamp.
Default: noneGenerated: no
statustextNot null
Lifecycle status.
Default: noneGenerated: no
Enumerated values:completedpendingreturned
coupon_codetextNullable
Column from the visible SQL schema.
Default: noneGenerated: no
Enumerated values:GEAR10WELCOMENULL

Relationships

orders.customer_id can repeat across many visible rows and references one customers.customer_id value.
orders.staff_id can repeat across many visible rows and references one staff.staff_id value.
order_items.order_id may contain many rows for one orders row through orders.order_id.

Fan-out note: joining child rows into orders can multiply the parent grain unless you aggregate or filter at the intended relationship level.

Sample rows

orders visible sample rows
order_id	customer_id	staff_id	ordered_at	status	coupon_code
100	1	1	2026-01-02T15:15:00.000Z	completed	WELCOME
101	2	1	2026-01-05T20:30:00.000Z	completed	NULL
102	1	2	2026-01-05T20:30:00.000Z	returned	NULL
103	4	2	2026-02-01T14:00:00.000Z	pending	GEAR10

products5 visible rows

Grain

one row per sellable product

Columns

product_idintegerNot nullKeyUniqueIndexed
Stable product key.
Default: noneGenerated: no
product_nametextNot null
Human-readable product name.
Default: noneGenerated: no
Enumerated values:Camp MugLanternNotebookTea TinTrail Mix
categorytextNullable
Optional merchandising category.
Default: noneGenerated: no
Enumerated values:GearSnacksStationeryNULL
pricenumericNot null
Current list price.
Default: noneGenerated: no
discontinuedbooleanNot null
Column from the visible SQL schema.
Default: falseGenerated: no
Enumerated values:falsetrue
stock_countintegerNot null
Column from the visible SQL schema.
Default: noneGenerated: no
restock_datedateNullable
Column from the visible SQL schema.
Default: noneGenerated: no

Relationships

order_items.product_id may contain many rows for one products row through products.product_id.

Fan-out note: joining child rows into products can multiply the parent grain unless you aggregate or filter at the intended relationship level.

Sample rows

products visible sample rows
product_id	product_name	category	price	discontinued	stock_count	restock_date
1	Trail Mix	Snacks	6.50	false	18	2026-01-15T00:00:00.000Z
2	Camp Mug	Gear	14.00	false	8	2026-01-20T00:00:00.000Z
3	Notebook	Stationery	4.25	false	0	NULL
4	Lantern	Gear	28.00	true	3	2026-02-01T00:00:00.000Z
5	Tea Tin	NULL	9.75	false	11	2026-01-31T00:00:00.000Z

staff2 visible rows

Grain

one row per staff member

Columns

staff_idintegerNot nullKeyUniqueIndexed
Stable staff key.
Default: noneGenerated: no
staff_nametextNot null
Staff display name.
Default: noneGenerated: no
Enumerated values:Riley ChenSam Patel
roletextNot null
Operational role.
Default: noneGenerated: no
Enumerated values:floorsupport

Relationships

orders.staff_id may contain many rows for one staff row through staff.staff_id.

Fan-out note: joining child rows into staff can multiply the parent grain unless you aggregate or filter at the intended relationship level.

Sample rows

staff visible sample rows
staff_id	staff_name	role
1	Riley Chen	floor
2	Sam Patel	support

History

Run Selection, Run All, or Explain Plan to build local history.

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Visible safety policyNo mastery effect

Engine cold Active scratch: Starter product scan.

Unchanged since last Run/CheckPlayground has no mastery effect

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Results

No result yet

Query output appears here. Result grids scroll inside the panel.

customer_id

customer_name

city

loyalty_tier

created_at

Avery Stone

Austin

gold

2025-12-01T00:00:00.000Z

Jordan Lee

Chicago

NULL

2026-01-03T00:00:00.000Z

Casey Quinn

Austin

silver

2026-01-04T00:00:00.000Z

Morgan Park

Seattle

gold

2026-01-09T00:00:00.000Z

Jordan Lee

Denver

NULL

2026-01-10T00:00:00.000Z

order_item_id

order_id

product_id

quantity

unit_price

1000

100

6.50

1001

100

14.00

1002

101

4.25

1003

102

6.50

1004

103

28.00

order_id

customer_id

staff_id

ordered_at

status

coupon_code

100

2026-01-02T15:15:00.000Z

completed

WELCOME

101

2026-01-05T20:30:00.000Z

completed

NULL

102

2026-01-05T20:30:00.000Z

returned

NULL

103

2026-02-01T14:00:00.000Z

pending

GEAR10

product_id

product_name