ClickHouse/docs/en/sql_reference/ansi.md

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40	ANSI Compatibility

ANSI SQL Compatibility of ClickHouse SQL Dialect

!!! note "Note" This article relies on Table 38, “Feature taxonomy and definition for mandatory features”, Annex F of ISO/IEC CD 9075-2:2013.

Differences in Behaviour

The following table lists cases when query feature works in ClickHouse, but behaves not as specified in ANSI SQL.

Feature ID	Feature Name	Difference
E011	Numeric data types	Numeric literal with period is interpreted as approximate (Float64) instead of exact (Decimal)
E051-05	Select items can be renamed	Item renames have a wider visibility scope than just the SELECT result
E141-01	NOT NULL constraints	NOT NULL is implied for table columns by default
E011-04	Arithmetic operators	ClickHouse overflows instead of checked arithmetic and changes the result data type based on custom rules

Feature Status

Feature ID	Feature Name	Status	Comment
E011	Numeric data types	Partial{.text-warning}
E011-01	INTEGER and SMALLINT data types	Yes{.text-success}
E011-02	REAL, DOUBLE PRECISION and FLOAT data types data types	Partial{.text-warning}	FLOAT(<binary_precision>), REAL and DOUBLE PRECISION are not supported
E011-03	DECIMAL and NUMERIC data types	Partial{.text-warning}	Only DECIMAL(p,s) is supported, not NUMERIC
E011-04	Arithmetic operators	Yes{.text-success}
E011-05	Numeric comparison	Yes{.text-success}
E011-06	Implicit casting among the numeric data types	No{.text-danger}	ANSI SQL allows arbitrary implicit cast between numeric types, while ClickHouse relies on functions having multiple overloads instead of implicit cast
E021	Character string types	Partial{.text-warning}
E021-01	CHARACTER data type	No{.text-danger}
E021-02	CHARACTER VARYING data type	No{.text-danger}	String behaves similarly, but without length limit in parentheses
E021-03	Character literals	Partial{.text-warning}	No automatic concatenation of consecutive literals and character set support
E021-04	CHARACTER_LENGTH function	Partial{.text-warning}	No USING clause
E021-05	OCTET_LENGTH function	No{.text-danger}	LENGTH behaves similarly
E021-06	SUBSTRING	Partial{.text-warning}	No support for SIMILAR and ESCAPE clauses, no SUBSTRING_REGEX variant
E021-07	Character concatenation	Partial{.text-warning}	No COLLATE clause
E021-08	UPPER and LOWER functions	Yes{.text-success}
E021-09	TRIM function	Yes{.text-success}
E021-10	Implicit casting among the fixed-length and variable-length character string types	No{.text-danger}	ANSI SQL allows arbitrary implicit cast between string types, while ClickHouse relies on functions having multiple overloads instead of implicit cast
E021-11	POSITION function	Partial{.text-warning}	No support for IN and USING clauses, no POSITION_REGEX variant
E021-12	Character comparison	Yes{.text-success}
E031	Identifiers	Partial{.text-warning}
E031-01	Delimited identifiers	Partial{.text-warning}	Unicode literal support is limited
E031-02	Lower case identifiers	Yes{.text-success}
E031-03	Trailing underscore	Yes{.text-success}
E051	Basic query specification	Partial{.text-warning}
E051-01	SELECT DISTINCT	Yes{.text-success}
E051-02	GROUP BY clause	Yes{.text-success}
E051-04	GROUP BY can contain columns not in <select list>	Yes{.text-success}
E051-05	Select items can be renamed	Yes{.text-success}
E051-06	HAVING clause	Yes{.text-success}
E051-07	Qualified * in select list	Yes{.text-success}
E051-08	Correlation name in the FROM clause	Yes{.text-success}
E051-09	Rename columns in the FROM clause	No{.text-danger}
E061	Basic predicates and search conditions	Partial{.text-warning}
E061-01	Comparison predicate	Yes{.text-success}
E061-02	BETWEEN predicate	Partial{.text-warning}	No SYMMETRIC and ASYMMETRIC clause
E061-03	IN predicate with list of values	Yes{.text-success}
E061-04	LIKE predicate	Yes{.text-success}
E061-05	LIKE predicate: ESCAPE clause	No{.text-danger}
E061-06	NULL predicate	Yes{.text-success}
E061-07	Quantified comparison predicate	No{.text-danger}
E061-08	EXISTS predicate	No{.text-danger}
E061-09	Subqueries in comparison predicate	Yes{.text-success}
E061-11	Subqueries in IN predicate	Yes{.text-success}
E061-12	Subqueries in quantified comparison predicate	No{.text-danger}
E061-13	Correlated subqueries	No{.text-danger}
E061-14	Search condition	Yes{.text-success}
E071	Basic query expressions	Partial{.text-warning}
E071-01	UNION DISTINCT table operator	No{.text-danger}
E071-02	UNION ALL table operator	Yes{.text-success}
E071-03	EXCEPT DISTINCT table operator	No{.text-danger}
E071-05	Columns combined via table operators need not have exactly the same data type	Yes{.text-success}
E071-06	Table operators in subqueries	Yes{.text-success}
E081	Basic privileges	Partial{.text-warning}	Work in progress
E091	Set functions	Yes{.text-success}
E091-01	AVG	Yes{.text-success}
E091-02	COUNT	Yes{.text-success}
E091-03	MAX	Yes{.text-success}
E091-04	MIN	Yes{.text-success}
E091-05	SUM	Yes{.text-success}
E091-06	ALL quantifier	No{.text-danger}
E091-07	DISTINCT quantifier	Partial{.text-warning}	Not all aggregate functions supported
E101	Basic data manipulation	Partial{.text-warning}
E101-01	INSERT statement	Yes{.text-success}	Note: primary key in ClickHouse does not imply the UNIQUE constraint
E101-03	Searched UPDATE statement	No{.text-danger}	There’s an ALTER UPDATE statement for batch data modification
E101-04	Searched DELETE statement	No{.text-danger}	There’s an ALTER DELETE statement for batch data removal
E111	Single row SELECT statement	No{.text-danger}
E121	Basic cursor support	No{.text-danger}
E121-01	DECLARE CURSOR	No{.text-danger}
E121-02	ORDER BY columns need not be in select list	No{.text-danger}
E121-03	Value expressions in ORDER BY clause	No{.text-danger}
E121-04	OPEN statement	No{.text-danger}
E121-06	Positioned UPDATE statement	No{.text-danger}
E121-07	Positioned DELETE statement	No{.text-danger}
E121-08	CLOSE statement	No{.text-danger}
E121-10	FETCH statement: implicit NEXT	No{.text-danger}
E121-17	WITH HOLD cursors	No{.text-danger}
E131	Null value support (nulls in lieu of values)	Partial{.text-warning}	Some restrictions apply
E141	Basic integrity constraints	Partial{.text-warning}
E141-01	NOT NULL constraints	Yes{.text-success}	Note: NOT NULL is implied for table columns by default
E141-02	UNIQUE constraint of NOT NULL columns	No{.text-danger}
E141-03	PRIMARY KEY constraints	No{.text-danger}
E141-04	Basic FOREIGN KEY constraint with the NO ACTION default for both referential delete action and referential update action	No{.text-danger}
E141-06	CHECK constraint	Yes{.text-success}
E141-07	Column defaults	Yes{.text-success}
E141-08	NOT NULL inferred on PRIMARY KEY	Yes{.text-success}
E141-10	Names in a foreign key can be specified in any order	No{.text-danger}
E151	Transaction support	No{.text-danger}
E151-01	COMMIT statement	No{.text-danger}
E151-02	ROLLBACK statement	No{.text-danger}
E152	Basic SET TRANSACTION statement	No{.text-danger}
E152-01	SET TRANSACTION statement: ISOLATION LEVEL SERIALIZABLE clause	No{.text-danger}
E152-02	SET TRANSACTION statement: READ ONLY and READ WRITE clauses	No{.text-danger}
E153	Updatable queries with subqueries	No{.text-danger}
E161	SQL comments using leading double minus	Yes{.text-success}
E171	SQLSTATE support	No{.text-danger}
E182	Host language binding	No{.text-danger}
F031	Basic schema manipulation	Partial{.text-warning}
F031-01	CREATE TABLE statement to create persistent base tables	Partial{.text-warning}	No SYSTEM VERSIONING, ON COMMIT, GLOBAL, LOCAL, PRESERVE, DELETE, REF IS, WITH OPTIONS, UNDER, LIKE, PERIOD FOR clauses and no support for user resolved data types
F031-02	CREATE VIEW statement	Partial{.text-warning}	No RECURSIVE, CHECK, UNDER, WITH OPTIONS clauses and no support for user resolved data types
F031-03	GRANT statement	Yes{.text-success}
F031-04	ALTER TABLE statement: ADD COLUMN clause	Partial{.text-warning}	No support for GENERATED clause and system time period
F031-13	DROP TABLE statement: RESTRICT clause	No{.text-danger}
F031-16	DROP VIEW statement: RESTRICT clause	No{.text-danger}
F031-19	REVOKE statement: RESTRICT clause	No{.text-danger}
F041	Basic joined table	Partial{.text-warning}
F041-01	Inner join (but not necessarily the INNER keyword)	Yes{.text-success}
F041-02	INNER keyword	Yes{.text-success}
F041-03	LEFT OUTER JOIN	Yes{.text-success}
F041-04	RIGHT OUTER JOIN	Yes{.text-success}
F041-05	Outer joins can be nested	Yes{.text-success}
F041-07	The inner table in a left or right outer join can also be used in an inner join	Yes{.text-success}
F041-08	All comparison operators are supported (rather than just =)	No{.text-danger}
F051	Basic date and time	Partial{.text-warning}
F051-01	DATE data type (including support of DATE literal)	Partial{.text-warning}	No literal
F051-02	TIME data type (including support of TIME literal) with fractional seconds precision of at least 0	No{.text-danger}
F051-03	TIMESTAMP data type (including support of TIMESTAMP literal) with fractional seconds precision of at least 0 and 6	No{.text-danger}	DateTime64 time provides similar functionality
F051-04	Comparison predicate on DATE, TIME, and TIMESTAMP data types	Partial{.text-warning}	Only one data type available
F051-05	Explicit CAST between datetime types and character string types	Yes{.text-success}
F051-06	CURRENT_DATE	No{.text-danger}	today() is similar
F051-07	LOCALTIME	No{.text-danger}	now() is similar
F051-08	LOCALTIMESTAMP	No{.text-danger}
F081	UNION and EXCEPT in views	Partial{.text-warning}
F131	Grouped operations	Partial{.text-warning}
F131-01	WHERE, GROUP BY, and HAVING clauses supported in queries with grouped views	Yes{.text-success}
F131-02	Multiple tables supported in queries with grouped views	Yes{.text-success}
F131-03	Set functions supported in queries with grouped views	Yes{.text-success}
F131-04	Subqueries with GROUP BY and HAVING clauses and grouped views	Yes{.text-success}
F131-05	Single row SELECT with GROUP BY and HAVING clauses and grouped views	No{.text-danger}
F181	Multiple module support	No{.text-danger}
F201	CAST function	Yes{.text-success}
F221	Explicit defaults	No{.text-danger}
F261	CASE expression	Yes{.text-success}
F261-01	Simple CASE	Yes{.text-success}
F261-02	Searched CASE	Yes{.text-success}
F261-03	NULLIF	Yes{.text-success}
F261-04	COALESCE	Yes{.text-success}
F311	Schema definition statement	Partial{.text-warning}
F311-01	CREATE SCHEMA	No{.text-danger}
F311-02	CREATE TABLE for persistent base tables	Yes{.text-success}
F311-03	CREATE VIEW	Yes{.text-success}
F311-04	CREATE VIEW: WITH CHECK OPTION	No{.text-danger}
F311-05	GRANT statement	Yes{.text-success}
F471	Scalar subquery values	Yes{.text-success}
F481	Expanded NULL predicate	Yes{.text-success}
F812	Basic flagging	No{.text-danger}
T321	Basic SQL-invoked routines	No{.text-danger}
T321-01	User-defined functions with no overloading	No{.text-danger}
T321-02	User-defined stored procedures with no overloading	No{.text-danger}
T321-03	Function invocation	No{.text-danger}
T321-04	CALL statement	No{.text-danger}
T321-05	RETURN statement	No{.text-danger}
T631	IN predicate with one list element	Yes{.text-success}