README.md
Erma
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Tasty SQL for Erlang
SQL builder for Erlang inspired by Korma, Tasty SQL for Clojure
Erma is a DSL language to describe and generate SQL queries. Erma is not a db driver. Erma doesn’t connect to db, doesn’t send requests.
SELECT
Q1 = {select, [], "user"},
S1 = <<"SELECT * FROM \"user\"">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = {select, ["first_name", "last_name", "address.state"], "user",
[{where, [{"email", "some@where.com"}]}]},
S2 = <<"SELECT first_name, last_name, address.\"state\" FROM \"user\" ",
"WHERE email = 'some@where.com'">>,
?assertEqual(S2, erma:build(Q2)),
Q3 = {select, ["id", "username"], "users",
[{where, [{"username", "chris"}]},
{order, ["created"]},
{offset, 3, limit, 5}]},
S3 = <<"SELECT id, username FROM users ",
"WHERE username = 'chris' ",
"ORDER BY created ASC ",
"OFFSET 3 LIMIT 5">>,
?assertEqual(S3, erma:build(Q3)),
INSERT
Q1 = {insert, "users", ["first", "last", "age"], ["Bob", "Dou", 25]},
S1 = <<"INSERT INTO users (\"first\", \"last\", age) VALUES ('Bob', 'Dou', 25)">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = {insert_rows, "users", ["first", "last", "age"],
[["Bill", "Foo", 24], ["Bob", "Dou", 25], ["Helen", "Rice", 21]]},
S2 = <<"INSERT INTO users (\"first\", \"last\", age) ",
"VALUES ('Bill', 'Foo', 24), ('Bob', 'Dou', 25), ('Helen', 'Rice', 21)">>,
?assertEqual(S2, erma:build(Q2)),
Q3 = {insert_rows, "users", [],
[[1, "Bob", "Dou", 65], [6, "Bill", "Foo", 31]],
[{returning, id}]},
S3 = <<"INSERT INTO users "
"VALUES (1, 'Bob', 'Dou', 65), (6, 'Bill', 'Foo', 31) ",
"RETURNING id">>,
?assertEqual(S3, erma:build(Q3)),
UPDATE
Q1 = {update, "users",
[{"first", "Chris"},
{"last", "Granger"}],
[{where, [{"id", 3}]}]},
S1 = <<"UPDATE users SET \"first\" = 'Chris', \"last\" = 'Granger' WHERE id = 3">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = {update, "users", [{"first", "Chris"}, {"last", "?"}], [{where, [{"id", "?"}]}]},
S2 = <<"UPDATE users SET \"first\" = 'Chris', \"last\" = ? WHERE id = ?">>,
?assertEqual(S2, erma:build(Q2)),
Q3 = {update, "users", [{"first", "Chris"}, {"last", "Granger"}],
[{where, [{"id", 3}]}, {returning, id}]},
S3 = <<"UPDATE users SET \"first\" = 'Chris', \"last\" = 'Granger' ",
"WHERE id = 3 RETURNING id">>,
?assertEqual(S3, erma:build(Q3)),
DELETE
Q1 = {delete, "users", [{where, [{"id", 3}]}]},
S1 = <<"DELETE FROM users WHERE id = 3">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = {delete, "users", [{where, [{"id", 3}]}, {returning, id}]},
S2 = <<"DELETE FROM users WHERE id = 3 RETURNING id">>,
?assertEqual(S2, erma:build(Q2)),
Join tables
Q1 = {select, ["email.email", "address.state", "account.name"], "user",
[{joins, [{left, "email"},
{left, <<"address">>},
{left, account}]}]},
S1 = <<"SELECT email.email, address.\"state\", account.\"name\" FROM \"user\" ",
"LEFT JOIN email ON email.id = \"user\".email_id ",
"LEFT JOIN address ON address.id = \"user\".address_id ",
"LEFT JOIN account ON account.id = \"user\".account_id">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = {select, ["email.email", "address.state", "account.name"], {"user", as, "u"},
[{joins, [{left, {"email", as, "e"}, [{pk, "eid"}]},
{right, "address", [{fk, "addr_id"}]},
{full, "account", [{pk, "aid"}, {fk, "acc_id"}]}]}]},
S2 = <<"SELECT email.email, address.\"state\", account.\"name\" FROM \"user\" AS u ",
"LEFT JOIN email AS e ON e.eid = u.email_id ",
"RIGHT JOIN address ON address.id = u.addr_id ",
"FULL JOIN account ON account.aid = u.acc_id">>,
?assertEqual(S2, erma:build(Q2)),
Compound where conditions
Q1 = {select, [], "post",
[{where, [{'or', [{"title", like, "%funny%"},
{"subject", like, "%funny%"},
{"content", like, "%funny%"}]}
]}
]},
S1 = <<"SELECT * FROM post ",
"WHERE (title LIKE '%funny%' OR subject LIKE '%funny%' OR content LIKE '%funny%')">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = {select, [], "post",
[{where, [{"state", in, ["active", "suspended", "unknown"]}]}
]},
S2 = <<"SELECT * FROM post ",
"WHERE \"state\" IN ('active', 'suspended', 'unknown')">>,
?assertEqual(S2, erma:build(Q2)),
DT1 = {datetime, {{2014, 1, 1}, {22, 30, 0}}},
DT2 = {datetime, {{2013, 12, 20}, {12, 15, 0}}},
Q3 = {select, [], "post",
[{where, [{'or', [{"title", like, "%funny%"},
{"subject", like, "%funny%"},
{"content", like, "%funny%"}]},
{'and', [{"blocked", false},
{'or', [{"posted", '>', DT1},
{"posted", '<', DT2}]}]},
{'not', {'or', [{"user_id", 20},
{"user_id", 30}]}},
{"state", in, ["active", "suspended", "unknown"]}
]}
]},
S3 = <<"SELECT * FROM post ",
"WHERE (title LIKE '%funny%' OR subject LIKE '%funny%' OR content LIKE '%funny%') ",
"AND (blocked = false AND "
"(posted > '2014-01-01 22:30:00' OR posted < '2013-12-20 12:15:00')) ",
"AND (NOT (user_id = 20 OR user_id = 30)) ",
"AND \"state\" IN ('active', 'suspended', 'unknown')">>,
?assertEqual(S3, erma:build(Q3)),
Append more joins and where conditions to query
Q1 = {select, [], "post"},
S1 = <<"SELECT * FROM post">>,
?assertEqual(S1, erma:build(Q1)),
Q2 = erma:append(Q1, [{where, [{"user_id", 10}]}]),
S2 = <<"SELECT * FROM post WHERE user_id = 10">>,
?assertEqual(S2, erma:build(Q2)),
Q3 = erma:append(Q2, [{where, [{'not', {"blocked", true}},
{"posted", '>', {date, {2014, 2, 20}}}]}]),
S3 = <<"SELECT * FROM post ",
"WHERE user_id = 10 AND (NOT blocked = true) AND posted > '2014-02-20'">>,
?assertEqual(S3, erma:build(Q3)),
Q4 = {select, ["u.id", "email.email", "a.state", "account.name"], {"user", as, "u"},
[{joins, [{left, "email"}]}]},
Q5 = erma:append(Q4, [{joins, [{left, {"address", as, "a"}}, {right, "account"}]}]),
S5 = <<"SELECT u.id, email.email, \"a\".\"state\", account.\"name\" ",
"FROM \"user\" AS u ",
"LEFT JOIN email ON email.id = u.email_id ",
"LEFT JOIN address AS \"a\" ON \"a\".id = u.address_id ",
"RIGHT JOIN account ON account.id = u.account_id">>,
?assertEqual(S5, erma:build(Q5)),
Resolve placeholders
Q1 = {select, [], "users", [{where, [{"name", {pl, "John"}}, {"age", gt, {pl, 18}}]}]},
Q2 = {select, [], "users", [{where, [{"name", "$1"}, {"age", gt, "$2"}]}]},
Args2 = ["John", 18],
?assertEqual({Q2, Args2}, erma:resolve_placeholders(Q1)),
Q3 = {insert, "users", ["first", <<"last">>, age], [123, {pl, 456}, {pl, 789}, 4242]},
Q4 = {insert, "users", ["first", <<"last">>, age], [123, "$1", "$2", 4242]},
Args4 = [456, 789],
?assertEqual({Q4, Args4}, erma:resolve_placeholders(Q3)),
Options
erma:build/2 accept options as second argument.Currently the only option supported is database.
erma:build(Q, #{database => postgresql}),
erma:build(Q, #{database => mysql}),
Options affect field and table names escaping and value placeholders. Mysql uses apostrophes to escape names and “?” as placehodlers. Postgresql uses single quotes to escape names and “$1, $2, $3” symbols as placeholders.
See unit tests for more samples.
[gh]: https://github.com/yzh44yzh/erma/actions/workflows/ci.yml [gh badge]: https://img.shields.io/github/workflow/status/yzh44yzh/erma/CI?style=flat-square [erlang version badge]: https://img.shields.io/badge/erlang-20.3%20to%2024.2-blue.svg?style=flat-squareКонвейеры
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