Julian Hyde created CALCITE-4484: ------------------------------------ Summary: Add UNIQUE_VALUE(x) aggregate function, that throws if x is not unique Key: CALCITE-4484 URL: https://issues.apache.org/jira/browse/CALCITE-4484 Project: Calcite Issue Type: Bug Reporter: Julian Hyde
Add a {{UNIQUE_VALUE\(x)}} aggregate function, that throws if {{x}} is not unique. {{UNIQUE_VALUE\(x)}} would throw if {{x}} has values [1, 2], or has values [1, NULL]; but would not throw if x has values [1, 1, 1] or [] or [NULL, NULL]. Like {{ANY_VALUE}} it behaves as if {{RESPECT NULLS}} is specified. There are similar functions: * {{ANY_VALUE\(x)}} non-deterministically picks a value. (It is present in BigQuery, MySQL, Snowflake, MSSQL and perhaps others.) * {{SINGLE_VALUE\(x)}} returns the value of x if there is just one value (e.g. [1] or [NULL]), NULL if there are no values, throws if there is more than one value (e.g. [NULL, NULL] or [1, 1, 1] or [1, 2]). {{SINGLE_VALUE}} is in Calcite, no other DBs that I am aware of, not documented, but available through SQL. Calcite uses it internally to enforce scalar sub-queries. BigQuery has an internal function "{{$ANY_AND_CHECK\(x)}}" that is equivalent to {{UNIQUE_VALUE\(x)}}. -- This message was sent by Atlassian Jira (v8.3.4#803005)