pysqlscribe 0.0.5

A simple Python Library for building relational database queries using objects

Overview

This is pysqlscribe, the Python library intended to make building SQL queries in your code a bit easier!

Motivation

Other query building libraries, such as pypika are fantastic but not actively maintained. Some ORM libraries such as sqlalchemy offer similar (and awesome) capabilities using the core API, but if you're not already using the library in your application, it's a bit of a large dependency to introduce for the purposes of query building.

API

pysqlscribe currently offers several APIs for building queries.

Query

A Query object can be constructed using the QueryRegistry's get_builder if you supply a valid dialect (e.g; "mysql", "postgres", "oracle). For example, "mysql" would be:

from pysqlscribe.query import QueryRegistry

query_builder = QueryRegistry.get_builder("mysql")
query = query_builder.select("test_column", "another_test_column").from_("test_table").build()

Alternatively, you can create the corresponding Query class associated with the dialect directly:

from pysqlscribe.query import MySQLQuery

query_builder = MySQLQuery()
query = query_builder.select("test_column", "another_test_column").from_("test_table").build()

In both cases, the output is:

SELECT `test_column`,`another_test_column` FROM `test_table`

Furthermore, if there are any dialects that we currently don't support, you can create your own by subclassing Query and registering it with the QueryRegistry:

from pysqlscribe.query import QueryRegistry, Query


@QueryRegistry.register("custom")
class CustomQuery(Query):
    ...

Table

An alternative method for building queries is through the Table object:

from pysqlscribe.table import MySQLTable

table = MySQLTable("test_table", "test_column", "another_test_column")
query = table.select("test_column").build()

Output:

SELECT `test_column` FROM `test_table`

A schema for the table can also be provided as a keyword argument, after the columns:

from pysqlscribe.table import MySQLTable

table = MySQLTable("test_table", "test_column", "another_test_column", schema="test_schema")
query = table.select("test_column").build()

Output:

SELECT `test_column` FROM `test_schema.test_table`

Table also offers a create method in the event you've added a new dialect which doesn't have an associated Table implementation, or if you need to change it for different environments (e.g; sqlite for local development, mysql/postgres/oracle/etc. for deployment):

from pysqlscribe.table import Table

new_dialect_table_class = Table.create(
    "new-dialect")  # assuming you've registered "new-dialect" with the `QueryRegistry`
table = new_dialect_table_class("test_table", "test_column", "another_test_column")

You can overwrite the original columns supplied to a Table as well, which will delete the old attributes and set new ones:

from pysqlscribe.table import MySQLTable

table = MySQLTable("test_table", "test_column", "another_test_column")
table.test_column  # valid
table.fields = ['new_test_column']
table.select("new_test_column")
table.new_test_column  # now valid - but `table.test_column` is not anymore

Additionally, you can reference the Column attributes Table object when constructing queries. For example, in a WHERE clause:

from pysqlscribe.table import PostgresTable

table = PostgresTable("employee", "first_name", "last_name", "salary", "location")
table.select("first_name", "last_name", "location").where(table.salary > 1000).build()

Output:

SELECT "first_name","last_name","location" FROM "employee" WHERE salary > 1000

For computing aggregates (e.g; MAX, AVG, COUNT), we have functions available in the aggregate_functions module which will accept both strings or columns:

from pysqlscribe.table import PostgresTable
from pysqlscribe.aggregate_functions import max_
table = PostgresTable(
    "employee", "first_name", "last_name", "store_location", "salary"
)
query = (
    table.select(table.store_location, max_(table.salary))
    .group_by(table.store_location)
    .build()
)
# Equivalently:
query_with_strs = (
    table.select("store_location", max_("salary"))
    .group_by("store_location")
    .build()
)

Output:

SELECT "store_location",MAX(salary) FROM "employee" GROUP BY "store_location"

Schema

For associating multiple Tables with a single schema, you can use the Schema:

from pysqlscribe.schema import Schema

schema = Schema("test_schema", tables=["test_table", "another_test_table"], dialect="postgres")
schema.tables  # a list of two `Table` objects

This is functionally equivalent to:

from pysqlscribe.table import PostgresTable

table = PostgresTable("test_table", schema="test_schema")
another_table = PostgresTable("another_test_table", schema="test_schema")

Instead of supplying a dialect directly to Schema, you can also set the environment variable PYQUERY_BUILDER_DIALECT:

export PYQUERY_BUILDER_DIALECT = 'postgres'

from pysqlscribe.schema import Schema

schema = Schema("test_schema", tables=["test_table", "another_test_table"])
schema.tables  # a list of two `PostgresTable` objects

Alternatively, if you already have existing Table objects you want to associate with the schema, you can supply them directly (in this case, dialect is not needed):

from pysqlscribe.schema import Schema
from pysqlscribe.table import PostgresTable

table = PostgresTable("test_table")
another_table = PostgresTable("another_test_table")
schema = Schema("test_schema", [table, another_table])

Schema also has each table set as an attribute, so in the example above, you can do the following:

schema.test_table # will return the supplied table object with the name `"test_table"`

Supported Dialects

This is anticipated to grow, also there are certainly operations that are missing within dialects.

• MySQL
• Oracle
• Postgres
• Sqlite

TODO

• Add more dialects
• Support OFFSET for Oracle and SQLServer
• Support for aliases for tables and columns
• Support subqueries
• Improved injection mitigation

💡 Interested in contributing? Check out the Local Development & Contributions Guide.