Advanced filters

dataset provides two methods for running queries: table.find() and db.query(). The table find helper method provides limited, but simple filtering options:

results = table.find(column={operator: value})
# e.g.:
results = table.find(name={'like': '%mole rat%'})

A special form is using keyword searches on specific columns:

results = table.find(value=5)
# equal to:
results = table.find(value={'=': 5})

# Lists, tuples and sets are turned into `IN` queries:
results = table.find(category=('foo', 'bar'))
# equal to:
results = table.find(value={'in': ('foo', 'bar')})

The following comparison operators are supported:

Operator

Description

gt, >

Greater than

lt, <

Less than

gte, >=

Greater or equal

lte, <=

Less or equal

!=, <>, not

Not equal to a single value

in

Value is in the given sequence

like, ilike

Text search, ILIKE is case-insensitive. Use % as a wildcard

between, ..

Value is between two values in the given tuple

startswith

String starts with

endswith

String ends with

Querying for a specific value on a column that does not exist on the table will return no results.

You can also pass additional SQLAlchemy clauses into the table.find() method by falling back onto the SQLAlchemy core objects wrapped by dataset:

# Get the column `city` from the dataset table:
column = table.table.columns.city
# Define a SQLAlchemy clause:
clause = column.ilike('amsterda%')
# Query using the clause:
results = table.find(clause)

This can also be used to define combined OR clauses if needed (e.g. city = ‘Bla’ OR country = ‘Foo’).

Queries using raw SQL

To run more complex queries with JOINs, or to perform GROUP BY-style aggregation, you can also use db.query() to run raw SQL queries instead. This also supports paramterisation to avoid SQL injections.

Finally, you should consider falling back to SQLAlchemy core to construct queries if you are looking for a programmatic, composable method of generating SQL in Python.