What SQL syntax does ClickHouse support?

ClickHouse has complete support for SQL syntax, including features such as:

• SQL/JSON and JSON data type (SQL-2023)
• Window functions (SQL-2003)
• Common table expressions and recursive queries (SQL-1999)
• ROLLUP, CUBE, and GROUPING SETS (SQL-1999)
• Full support for RBAC (SQL-1999)
• Correlated subqueries (SQL-1992);

The support is validated by TPC-H and TPC-DS benchmarks, as well as by SQLTest.

ClickHouse introduced many features before they were subsequently standardised by ISO/IEC, such as:

• conditional aggregate functions
• any aggregate functions
• least and greatest
• GROUP BY ALL
• extended use of aliases
• underscores in numeric literals

ClickHouse extend the SQL by introducing major quality-of-life improvements:

• unrestricted use of aliases
• aliases inside the WITH clause
• aggregate function combinators
• parameterized aggregate functions
• approximate aggregate functions
• native and big integer numeric data types, extended precision decimal
• higher order functions for arrays manipulation
• ARRAY JOIN clause and arrayJoin function
• array aggregation
• LIMIT BY clause
• GROUP BY WITH TOTALS
• AS OF JOIN
• ANY/ALL JOIN
• natural syntax for JSON
• trailing comma in the column list
• FROM ... SELECT clause order
• type-safe query parameters and parameterized views

Some of them have a chance to be included in the upcoming SQL standards, while already being available for ClickHouse users.