Friendly SQL

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Documentation / Guides / SQL Features

Friendly SQL

DuckDB offers several advanced SQL features as well as extensions to the SQL syntax. We call these colloquially as "friendly SQL".

Several of these features are also supported in other systems while some are (currently) exclusive to DuckDB.

Clauses

Query Features

Column aliases in WHERE, GROUP BY, and HAVING
COLUMNS() expression
Reusable column aliases, e.g.: SELECT i + 1 AS j, j + 2 AS k FROM range(0, 3) t(i)

Literals and Identifiers

Data Types

Data Import

Auto-detecting the headers and schema of CSV files
Directly querying CSV files and Parquet files
Loading from files using the syntax FROM 'my.csv', FROM 'my.csv.gz', FROM 'my.parquet', etc.
Filename expansion (globbing), e.g.: FROM 'my-data/part-*.parquet'

Functions and Expressions

Dot operator for function chaining: SELECT ('hello').upper()
String formatters: format() function with the fmt syntax and the printf() function
List comprehensions
List slicing
String slicing
STRUCT.* notation
Simple LIST and STRUCT creation

Join Types

Trailing Commas

DuckDB allows trailing commas, both when listing entities (e.g., column and table names) and when constructing LIST items. For example, the following query works:

SELECT
    42 AS x,
    ['a', 'b', 'c',] AS y,
    'hello world' AS z,
;