A gist to be used with relax for queries in the relational algebra, https://dbis-uibk.github.io/relax/

relax-example

-- To be used with RelaX: https://dbis-uibk.github.io/relax/calc.htm
-- https://dbis-uibk.github.io/relax/calc/gist/02c807c63faf1d57d77f487d6a0726f4

group: bank example
description[[ Sample data for crash course on the Relational Model.
* Relation _Customer_ contains identifiers and names of customers of a bank.
* Relation _Account_ contains identifiers, customer IDs, types and balances of bank accounts. Note that a customer can have any number of accounts, while each account is owned by exactly one customer.
* Relation _BadAccount_ contains information about accounts and customers in one place.
* Query _SampleQuery_ return names of customers with high balances.
]]

Customer = { cid, name
1 Miller
2 Miller
42 Smith
}

Account = { aid cid type balance
1 42 Checking 1000
2 42 Savings 2000
3 1 Checking -300
42 2 Savings 10000000
}

BadAccount = { aid date cid type balance custage
1 2015-01-01 42 Checking 1000 42
2 2015-01-01 42 Savings 2000 42
3 2015-01-01 1 Checking -300 22
1 2015-01-02 42 Checking 960 43
}

SampleQuery =
  pi name, balance (
    Customer
      join
    sigma balance > 1000000 (Account) )