antcap96 / sqlinpython

sqlinpython

This is a small toy library to integrate SQL into a python project. The library allows to write python code that is very similar to a SQL query that then can be converted to the query string with the get_query method. The advantage this brings over having the raw strings in the code is editor auto-complete and static syntax check, since the library is fully type annotated.

The type checks are only made with external tools like mypy and are not made at runtime.

Examples

A simple example usage of this library might look like this:

from sqlinpython import Select, TableRef, ColumnRef
assert (
    Select(ColumnRef("a")).From(TableRef("b")).get_query()
    == 'SELECT a FROM b'
)

But the library is capable of much more complex queries like the following:

from sqlinpython import Select, TableRef, ColumnRef, Value, functions as f
(
    Select(ColumnRef("full_name"))
    .From(TableRef("SALES_PERSON"))
    .Where(ColumnRef("ranking") >= Value(5.0))
    .UnionAll(
        Select(ColumnRef("reviewer_name"))
        .From(TableRef("CUSTOMER_REVIEW"))
        .GroupBy(ColumnRef("reviewer_name"))
        .Having(f.Avg(ColumnRef("score")) >= Value(8.0))
    )
    .get_query()
)
output = 'SELECT full_name FROM SALES_PERSON WHERE ranking >= 5.0 UNION ALL SELECT reviewer_name FROM CUSTOMER_REVIEW GROUP BY reviewer_name HAVING AVG(score) >= 8.0'

Although for larger queries, for the sake of readability, you should probably split up the components into variables:

sales_people = (
    Select(ColumnRef("full_name"))
    .From(TableRef("SALES_PERSON"))
    .Where(ColumnRef("ranking") >= Value(5.0))
)
reviewers = (
    Select(ColumnRef("reviewer_name"))
    .From(TableRef("CUSTOMER_REVIEW"))
    .GroupBy(ColumnRef("reviewer_name"))
    .Having(f.Avg(ColumnRef("score")) >= Value(8.0))
)
sales_people.UnionAll(reviewers).get_query()

Further examples can be seen in the tests directory.

Potential problems

In order to only allow valid SQL syntax, the library creates hundreds of different types. A naming convention is adhered to try to make these types somewhat manageable, but it isn't always obvious what the type should be if you decide to create a function that outputs an incomplete sql query. For example, a select query of the type Select(...).From(...) has the type SelectStatementWithFrom, while the type of a select query of the type Select(...) has the type SelectStatementWithSelectExpression.

These types are not yet part of a public api and their names might be changed in the future.

State

The library is not yet complete, with some syntax not implemented.