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190 lines
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190 lines
56 KiB
Markdown
---
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toc_priority: 40
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toc_title: ANSI Compatibility
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---
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# ANSI SQL Compatibility of ClickHouse SQL Dialect {#ansi-sql-compatibility-of-clickhouse-sql-dialect}
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!!! note "Note"
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This article relies on Table 38, “Feature taxonomy and definition for mandatory features”, Annex F of [ISO/IEC CD 9075-2:2011](https://www.iso.org/obp/ui/#iso:std:iso-iec:9075:-2:ed-4:v1:en:sec:8).
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## Differences in Behaviour {#differences-in-behaviour}
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The following table lists cases when query feature works in ClickHouse, but behaves not as specified in ANSI SQL.
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| Feature ID | Feature Name | Difference |
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|------------|-----------------------------|-----------------------------------------------------------------------------------------------------------|
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| E011 | Numeric data types | Numeric literal with period is interpreted as approximate (`Float64`) instead of exact (`Decimal`) |
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| E051-05 | Select items can be renamed | Item renames have a wider visibility scope than just the SELECT result |
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| E141-01 | NOT NULL constraints | `NOT NULL` is implied for table columns by default |
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| E011-04 | Arithmetic operators | ClickHouse overflows instead of checked arithmetic and changes the result data type based on custom rules |
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## Feature Status {#feature-status}
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| Feature ID | Feature Name | Status | Comment |
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|------------|--------------------------------------------------------------------------------------------------------------------------|----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| **E011** | **Numeric data types** | **Partial**{.text-warning} | |
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| E011-01 | INTEGER and SMALLINT data types | Yes{.text-success} | |
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| E011-02 | REAL, DOUBLE PRECISION and FLOAT data types data types | Partial{.text-warning} | `FLOAT(<binary_precision>)`, `REAL` and `DOUBLE PRECISION` are not supported |
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| E011-03 | DECIMAL and NUMERIC data types | Partial{.text-warning} | Only `DECIMAL(p,s)` is supported, not `NUMERIC` |
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| E011-04 | Arithmetic operators | Yes{.text-success} | |
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| E011-05 | Numeric comparison | Yes{.text-success} | |
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| 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 |
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| **E021** | **Character string types** | **Partial**{.text-warning} | |
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| E021-01 | CHARACTER data type | No{.text-danger} | |
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| E021-02 | CHARACTER VARYING data type | No{.text-danger} | `String` behaves similarly, but without length limit in parentheses |
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| E021-03 | Character literals | Partial{.text-warning} | No automatic concatenation of consecutive literals and character set support |
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| E021-04 | CHARACTER_LENGTH function | Partial{.text-warning} | No `USING` clause |
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| E021-05 | OCTET_LENGTH function | No{.text-danger} | `LENGTH` behaves similarly |
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| E021-06 | SUBSTRING | Partial{.text-warning} | No support for `SIMILAR` and `ESCAPE` clauses, no `SUBSTRING_REGEX` variant |
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| E021-07 | Character concatenation | Partial{.text-warning} | No `COLLATE` clause |
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| E021-08 | UPPER and LOWER functions | Yes{.text-success} | |
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| E021-09 | TRIM function | Yes{.text-success} | |
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| 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 |
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| E021-11 | POSITION function | Partial{.text-warning} | No support for `IN` and `USING` clauses, no `POSITION_REGEX` variant |
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| E021-12 | Character comparison | Yes{.text-success} | |
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| **E031** | **Identifiers** | **Partial**{.text-warning} | |
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| E031-01 | Delimited identifiers | Partial{.text-warning} | Unicode literal support is limited |
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| E031-02 | Lower case identifiers | Yes{.text-success} | |
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| E031-03 | Trailing underscore | Yes{.text-success} | |
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| **E051** | **Basic query specification** | **Partial**{.text-warning} | |
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| E051-01 | SELECT DISTINCT | Yes{.text-success} | |
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| E051-02 | GROUP BY clause | Yes{.text-success} | |
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| E051-04 | GROUP BY can contain columns not in `<select list>` | Yes{.text-success} | |
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| E051-05 | Select items can be renamed | Yes{.text-success} | |
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| E051-06 | HAVING clause | Yes{.text-success} | |
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| E051-07 | Qualified \* in select list | Yes{.text-success} | |
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| E051-08 | Correlation name in the FROM clause | Yes{.text-success} | |
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| E051-09 | Rename columns in the FROM clause | No{.text-danger} | |
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| **E061** | **Basic predicates and search conditions** | **Partial**{.text-warning} | |
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| E061-01 | Comparison predicate | Yes{.text-success} | |
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| E061-02 | BETWEEN predicate | Partial{.text-warning} | No `SYMMETRIC` and `ASYMMETRIC` clause |
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| E061-03 | IN predicate with list of values | Yes{.text-success} | |
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| E061-04 | LIKE predicate | Yes{.text-success} | |
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| E061-05 | LIKE predicate: ESCAPE clause | No{.text-danger} | |
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| E061-06 | NULL predicate | Yes{.text-success} | |
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| E061-07 | Quantified comparison predicate | No{.text-danger} | |
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| E061-08 | EXISTS predicate | No{.text-danger} | |
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| E061-09 | Subqueries in comparison predicate | Yes{.text-success} | |
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| E061-11 | Subqueries in IN predicate | Yes{.text-success} | |
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| E061-12 | Subqueries in quantified comparison predicate | No{.text-danger} | |
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| E061-13 | Correlated subqueries | No{.text-danger} | |
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| E061-14 | Search condition | Yes{.text-success} | |
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| **E071** | **Basic query expressions** | **Partial**{.text-warning} | |
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| E071-01 | UNION DISTINCT table operator | No{.text-danger} | |
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| E071-02 | UNION ALL table operator | Yes{.text-success} | |
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| E071-03 | EXCEPT DISTINCT table operator | No{.text-danger} | |
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| E071-05 | Columns combined via table operators need not have exactly the same data type | Yes{.text-success} | |
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| E071-06 | Table operators in subqueries | Yes{.text-success} | |
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| **E081** | **Basic privileges** | **Partial**{.text-warning} | Work in progress |
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| E081-01 | SELECT privilege at the table level | | |
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| E081-02 | DELETE privilege | | |
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| E081-03 | INSERT privilege at the table level | | |
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| E081-04 | UPDATE privilege at the table level | | |
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| E081-05 | UPDATE privilege at the column level | | |
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| E081-06 | REFERENCES privilege at the table level | | |
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| E081-07 | REFERENCES privilege at the column level | | |
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| E081-08 | WITH GRANT OPTION | | |
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| E081-09 | USAGE privilege | | |
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| E081-10 | EXECUTE privilege | | |
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| **E091** | **Set functions** | **Yes**{.text-success} | |
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| E091-01 | AVG | Yes{.text-success} | |
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| E091-02 | COUNT | Yes{.text-success} | |
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| E091-03 | MAX | Yes{.text-success} | |
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| E091-04 | MIN | Yes{.text-success} | |
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| E091-05 | SUM | Yes{.text-success} | |
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| E091-06 | ALL quantifier | No{.text-danger} | |
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| E091-07 | DISTINCT quantifier | Partial{.text-warning} | Not all aggregate functions supported |
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| **E101** | **Basic data manipulation** | **Partial**{.text-warning} | |
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| E101-01 | INSERT statement | Yes{.text-success} | Note: primary key in ClickHouse does not imply the `UNIQUE` constraint |
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| E101-03 | Searched UPDATE statement | No{.text-danger} | There’s an `ALTER UPDATE` statement for batch data modification |
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| E101-04 | Searched DELETE statement | No{.text-danger} | There’s an `ALTER DELETE` statement for batch data removal |
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| **E111** | **Single row SELECT statement** | **No**{.text-danger} | |
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| **E121** | **Basic cursor support** | **No**{.text-danger} | |
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| E121-01 | DECLARE CURSOR | No{.text-danger} | |
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| E121-02 | ORDER BY columns need not be in select list | No{.text-danger} | |
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| E121-03 | Value expressions in ORDER BY clause | No{.text-danger} | |
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| E121-04 | OPEN statement | No{.text-danger} | |
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| E121-06 | Positioned UPDATE statement | No{.text-danger} | |
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| E121-07 | Positioned DELETE statement | No{.text-danger} | |
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| E121-08 | CLOSE statement | No{.text-danger} | |
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| E121-10 | FETCH statement: implicit NEXT | No{.text-danger} | |
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| E121-17 | WITH HOLD cursors | No{.text-danger} | |
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| **E131** | **Null value support (nulls in lieu of values)** | **Partial**{.text-warning} | Some restrictions apply |
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| **E141** | **Basic integrity constraints** | **Partial**{.text-warning} | |
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| E141-01 | NOT NULL constraints | Yes{.text-success} | Note: `NOT NULL` is implied for table columns by default |
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| E141-02 | UNIQUE constraint of NOT NULL columns | No{.text-danger} | |
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| E141-03 | PRIMARY KEY constraints | No{.text-danger} | |
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| E141-04 | Basic FOREIGN KEY constraint with the NO ACTION default for both referential delete action and referential update action | No{.text-danger} | |
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| E141-06 | CHECK constraint | Yes{.text-success} | |
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| E141-07 | Column defaults | Yes{.text-success} | |
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| E141-08 | NOT NULL inferred on PRIMARY KEY | Yes{.text-success} | |
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| E141-10 | Names in a foreign key can be specified in any order | No{.text-danger} | |
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| **E151** | **Transaction support** | **No**{.text-danger} | |
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| E151-01 | COMMIT statement | No{.text-danger} | |
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| E151-02 | ROLLBACK statement | No{.text-danger} | |
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| **E152** | **Basic SET TRANSACTION statement** | **No**{.text-danger} | |
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| E152-01 | SET TRANSACTION statement: ISOLATION LEVEL SERIALIZABLE clause | No{.text-danger} | |
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| E152-02 | SET TRANSACTION statement: READ ONLY and READ WRITE clauses | No{.text-danger} | |
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| **E153** | **Updatable queries with subqueries** | **No**{.text-danger} | |
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| **E161** | **SQL comments using leading double minus** | **Yes**{.text-success} | |
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| **E171** | **SQLSTATE support** | **No**{.text-danger} | |
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| **E182** | **Host language binding** | **No**{.text-danger} | |
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| **F031** | **Basic schema manipulation** | **Partial**{.text-warning} | |
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| 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 |
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| F031-02 | CREATE VIEW statement | Partial{.text-warning} | No `RECURSIVE`, `CHECK`, `UNDER`, `WITH OPTIONS` clauses and no support for user resolved data types |
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| F031-03 | GRANT statement | Yes{.text-success} | |
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| F031-04 | ALTER TABLE statement: ADD COLUMN clause | Partial{.text-warning} | No support for `GENERATED` clause and system time period |
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| F031-13 | DROP TABLE statement: RESTRICT clause | No{.text-danger} | |
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| F031-16 | DROP VIEW statement: RESTRICT clause | No{.text-danger} | |
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| F031-19 | REVOKE statement: RESTRICT clause | No{.text-danger} | |
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| **F041** | **Basic joined table** | **Partial**{.text-warning} | |
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| F041-01 | Inner join (but not necessarily the INNER keyword) | Yes{.text-success} | |
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| F041-02 | INNER keyword | Yes{.text-success} | |
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| F041-03 | LEFT OUTER JOIN | Yes{.text-success} | |
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| F041-04 | RIGHT OUTER JOIN | Yes{.text-success} | |
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| F041-05 | Outer joins can be nested | Yes{.text-success} | |
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| F041-07 | The inner table in a left or right outer join can also be used in an inner join | Yes{.text-success} | |
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| F041-08 | All comparison operators are supported (rather than just =) | No{.text-danger} | |
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| **F051** | **Basic date and time** | **Partial**{.text-warning} | |
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| F051-01 | DATE data type (including support of DATE literal) | Partial{.text-warning} | No literal |
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| F051-02 | TIME data type (including support of TIME literal) with fractional seconds precision of at least 0 | No{.text-danger} | |
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| 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 |
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| F051-04 | Comparison predicate on DATE, TIME, and TIMESTAMP data types | Partial{.text-warning} | Only one data type available |
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| F051-05 | Explicit CAST between datetime types and character string types | Yes{.text-success} | |
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| F051-06 | CURRENT_DATE | No{.text-danger} | `today()` is similar |
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| F051-07 | LOCALTIME | No{.text-danger} | `now()` is similar |
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| F051-08 | LOCALTIMESTAMP | No{.text-danger} | |
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| **F081** | **UNION and EXCEPT in views** | **Partial**{.text-warning} | |
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| **F131** | **Grouped operations** | **Partial**{.text-warning} | |
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| F131-01 | WHERE, GROUP BY, and HAVING clauses supported in queries with grouped views | Yes{.text-success} | |
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| F131-02 | Multiple tables supported in queries with grouped views | Yes{.text-success} | |
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| F131-03 | Set functions supported in queries with grouped views | Yes{.text-success} | |
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| F131-04 | Subqueries with GROUP BY and HAVING clauses and grouped views | Yes{.text-success} | |
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| F131-05 | Single row SELECT with GROUP BY and HAVING clauses and grouped views | No{.text-danger} | |
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| **F181** | **Multiple module support** | **No**{.text-danger} | |
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| **F201** | **CAST function** | **Yes**{.text-success} | |
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| **F221** | **Explicit defaults** | **No**{.text-danger} | |
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| **F261** | **CASE expression** | **Yes**{.text-success} | |
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| F261-01 | Simple CASE | Yes{.text-success} | |
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| F261-02 | Searched CASE | Yes{.text-success} | |
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| F261-03 | NULLIF | Yes{.text-success} | |
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| F261-04 | COALESCE | Yes{.text-success} | |
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| **F311** | **Schema definition statement** | **Partial**{.text-warning} | |
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| F311-01 | CREATE SCHEMA | No{.text-danger} | |
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| F311-02 | CREATE TABLE for persistent base tables | Yes{.text-success} | |
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| F311-03 | CREATE VIEW | Yes{.text-success} | |
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| F311-04 | CREATE VIEW: WITH CHECK OPTION | No{.text-danger} | |
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| F311-05 | GRANT statement | Yes{.text-success} | |
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| **F471** | **Scalar subquery values** | **Yes**{.text-success} | |
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| **F481** | **Expanded NULL predicate** | **Yes**{.text-success} | |
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| **F812** | **Basic flagging** | **No**{.text-danger} | |
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| **S011** | **Distinct data types** | | |
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| **T321** | **Basic SQL-invoked routines** | **No**{.text-danger} | |
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| T321-01 | User-defined functions with no overloading | No{.text-danger} | |
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| T321-02 | User-defined stored procedures with no overloading | No{.text-danger} | |
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| T321-03 | Function invocation | No{.text-danger} | |
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| T321-04 | CALL statement | No{.text-danger} | |
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| T321-05 | RETURN statement | No{.text-danger} | |
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| **T631** | **IN predicate with one list element** | **Yes**{.text-success} | |
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