brmbar-github/brmbar3/SQL

CREATE SEQUENCE currencies_id_seq START WITH 1 INCREMENT BY 1;
CREATE TABLE currencies (
	id INTEGER PRIMARY KEY NOT NULL DEFAULT NEXTVAL('currencies_id_seq'::regclass),
	name VARCHAR(128) NOT NULL,
	UNIQUE(name)
);
-- Some code depends on the primary physical currency to have id 1.
INSERT INTO currencies (name) VALUES ('Kč');

CREATE TYPE exchange_rate_direction AS ENUM ('source_to_target', 'target_to_source');
CREATE TABLE exchange_rates (
	valid_since TIMESTAMP WITHOUT TIME ZONE DEFAULT NOW() NOT NULL,

	target INTEGER NOT NULL,
        FOREIGN KEY (target) REFERENCES currencies (id),

	source INTEGER NOT NULL,
        FOREIGN KEY (source) REFERENCES currencies (id),

	rate DECIMAL(12,2) NOT NULL,
	rate_dir exchange_rate_direction NOT NULL
);


-- brmbar users have 'debt' accounts; a negative balance means that
-- we have debt to the users, i.e. they are positive relative to the brmbar.
-- Positive balance means that the users have debt in brmbar.
-- Therefore, user's balance must always be shown negated.
CREATE SEQUENCE accounts_id_seq START WITH 1 INCREMENT BY 1;
CREATE TYPE account_type AS ENUM ('cash', 'debt', 'inventory', 'income', 'expense', 'starting_balance', 'ending_balance');
CREATE TABLE accounts (
	id INTEGER PRIMARY KEY NOT NULL DEFAULT NEXTVAL('accounts_id_seq'::regclass),

	name VARCHAR(128) NOT NULL,
	UNIQUE (name),

	currency INTEGER NOT NULL,
        FOREIGN KEY (currency) REFERENCES currencies (id),

	acctype account_type NOT NULL
);
INSERT INTO accounts (name, currency, acctype) VALUES ('BrmBar Cash', (SELECT id FROM currencies WHERE name='Kč'), 'cash');
INSERT INTO accounts (name, currency, acctype) VALUES ('BrmBar Profits', (SELECT id FROM currencies WHERE name='Kč'), 'income');
INSERT INTO accounts (name, currency, acctype) VALUES ('BrmBar Excess', (SELECT id FROM currencies WHERE name='Kč'), 'income');
INSERT INTO accounts (name, currency, acctype) VALUES ('BrmBar Deficit', (SELECT id FROM currencies WHERE name='Kč'), 'expense');


CREATE SEQUENCE barcodes_id_seq START WITH 1 INCREMENT BY 1;
CREATE TABLE barcodes (
	barcode VARCHAR(128) PRIMARY KEY NOT NULL,

	account INTEGER NOT NULL,
        FOREIGN KEY (account) REFERENCES accounts (id)
);
-- Barcode for cash
-- XXX Silently assume there is only one.
INSERT INTO barcodes (barcode, account) VALUES ('_cash_', (SELECT id FROM accounts WHERE acctype = 'cash'));


CREATE SEQUENCE transactions_id_seq START WITH 1 INCREMENT BY 1;
CREATE TABLE transactions (
	id INTEGER PRIMARY KEY NOT NULL DEFAULT NEXTVAL('transactions_id_seq'::regclass),
	time TIMESTAMP DEFAULT NOW() NOT NULL,

	responsible INTEGER,
	FOREIGN KEY (responsible) REFERENCES accounts (id),
	-- FIXME: imperfect constraint to assure this is a user

	description TEXT
);

CREATE SEQUENCE transaction_splits_id_seq START WITH 1 INCREMENT BY 1;
CREATE TYPE transaction_split_side AS ENUM ('credit', 'debit');
CREATE TABLE transaction_splits (
	id INTEGER PRIMARY KEY NOT NULL DEFAULT NEXTVAL('transaction_splits_id_seq'::regclass),

	transaction INTEGER NOT NULL,
	FOREIGN KEY (transaction) REFERENCES transactions (id),

	side transaction_split_side NOT NULL,

	account INTEGER NOT NULL,
        FOREIGN KEY (account) REFERENCES accounts (id),
	amount DECIMAL(12,2) NOT NULL,

	memo TEXT
);

-- List balances of accounts computed based on transactions
-- Note that currency information is currently not supplied; inventory items
-- have balances in stock amounts.
CREATE VIEW account_balances AS
	SELECT ts.account AS id, accounts.name AS name, accounts.acctype AS acctype,
		-SUM(CASE WHEN ts.side = 'credit' THEN -ts.amount ELSE ts.amount END) AS crbalance
		FROM transaction_splits AS ts
		LEFT JOIN accounts ON accounts.id = ts.account
		GROUP BY ts.account, accounts.name, accounts.acctype
		ORDER BY crbalance ASC;

-- Transaction splits in a form that's nicer to query during manual inspection
CREATE VIEW transaction_nicesplits AS
	SELECT ts.id AS id, ts.transaction AS transaction, ts.account AS account,
			(CASE WHEN ts.side = 'credit' THEN -ts.amount ELSE ts.amount END) AS amount,
			a.currency AS currency, ts.memo AS memo
		FROM transaction_splits AS ts LEFT JOIN accounts AS a ON a.id = ts.account
		ORDER BY ts.id;

-- List transactions with summary information regarding their cash element
-- (except in case of transfers between cash and debt accounts, which will cancel out).
CREATE VIEW transaction_cashsums AS
	SELECT t.id AS id, t.time AS time, SUM(credit_cash) AS cash_credit, SUM(debit_cash) AS cash_debit, t.description AS description
		FROM transactions AS t
		LEFT JOIN (SELECT cts.amount AS credit_cash, cts.transaction AS cts_t
				FROM transaction_nicesplits AS cts
			LEFT JOIN accounts AS a ON a.id = cts.account OR a.id = cts.account
			WHERE a.currency = (SELECT currency FROM accounts WHERE name = 'BrmBar Cash')
				AND a.acctype IN ('cash', 'debt')
				AND cts.amount < 0) credit ON cts_t = t.id
		LEFT JOIN (SELECT dts.amount AS debit_cash, dts.transaction AS dts_t
				FROM transaction_nicesplits AS dts
			LEFT JOIN accounts AS a ON a.id = dts.account OR a.id = dts.account
			WHERE a.currency = (SELECT currency FROM accounts WHERE name = 'BrmBar Cash')
				AND a.acctype IN ('cash', 'debt')
				AND dts.amount > 0) debit ON dts_t = t.id
		GROUP BY t.id ORDER BY t.id;