patito.duckdb.Relation.select

Relation.select(*projections, **named_projections)

Return relation based on one or more SQL SELECT projections.

Keyword arguments are converted into {arg} as {keyword} in the executed SQL query.

Parameters:

• *projections (Union[str, int, float]) – One or more strings representing SQL statements to be selected. For example "2" or "another_column".

• **named_projections (Union[str, int, float]) – One ore more keyword arguments where the keyword specifies the name of the new column and the value is an SQL statement defining the content of the new column. For example new_column="2 * another_column".

Return type:

Relation

Examples

>>> import patito as pt
>>> db = pt.duckdb.Database()
>>> relation = db.to_relation(pt.DataFrame({"original_column": [1, 2, 3]}))
>>> relation.select("*").to_df()
shape: (3, 1)
┌─────────────────┐
│ original_column │
│ ---             │
│ i64             │
╞═════════════════╡
│ 1               │
│ 2               │
│ 3               │
└─────────────────┘
>>> relation.select("*", multiplied_column="2 * original_column").to_df()
shape: (3, 2)
┌─────────────────┬───────────────────┐
│ original_column ┆ multiplied_column │
│ ---             ┆ ---               │
│ i64             ┆ i64               │
╞═════════════════╪═══════════════════╡
│ 1               ┆ 2                 │
│ 2               ┆ 4                 │
│ 3               ┆ 6                 │
└─────────────────┴───────────────────┘