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Add GREATEST(expr1, expr2, ... exprN) and LEAST(expr1, expr2, exprN) functions which are in the family of CONDITIONAL functions. Implementation follows PostgreSQL behaviour, so the functions return `NULL` when all of their arguments evaluate to `NULL`. Renamed `CoalescePipe` and `CoalesceProcessor` to `ConditionalPipe` and `ConditionalProcessor` respectively, to be able to reuse them for `Greatest` and `Least` evaluations. To achieve that `ConditionalOperation` has been added to differentiate between the functionalities at execution time. Closes: #35878
277 lines
4.9 KiB
Plaintext
277 lines
4.9 KiB
Plaintext
[role="xpack"]
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[testenv="basic"]
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[[sql-functions-conditional]]
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=== Conditional Functions
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Functions that return one of their arguments by evaluating in an if-else manner.
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[[sql-functions-conditional-coalesce]]
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==== `COALESCE`
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.Synopsis
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[source, sql]
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----
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COALESCE ( expression<1>, expression<2>, ... )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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...
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**N**th expression
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COALESCE can take an arbitrary number of arguments.
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*Output*: one of the expressions or `null`
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.Description
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Returns the first of its arguments that is not null.
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If all arguments are null, then it returns `null`.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[coalesceReturnNonNull]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[coalesceReturnNull]
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----
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[[sql-functions-conditional-ifnull]]
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==== `IFNULL`
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.Synopsis
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[source, sql]
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----
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IFNULL ( expression<1>, expression<2> )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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*Output*: 2nd expression if 1st expression is null, otherwise 1st expression.
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.Description
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Variant of <<sql-functions-conditional-coalesce>> with only two arguments.
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Returns the first of its arguments that is not null.
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If all arguments are null, then it returns `null`.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[ifNullReturnFirst]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[ifNullReturnSecond]
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----
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[[sql-functions-conditional-isnull]]
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==== `ISNULL`
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.Synopsis
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[source, sql]
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----
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ISNULL ( expression<1>, expression<2> )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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*Output*: 2nd expression if 1st expression is null, otherwise 1st expression.
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.Description
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Variant of <<sql-functions-conditional-coalesce>> with only two arguments.
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Returns the first of its arguments that is not null.
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If all arguments are null, then it returns `null`.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[isNullReturnFirst]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[isNullReturnSecond]
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----
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[[sql-functions-conditional-nvl]]
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==== `NVL`
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.Synopsis
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[source, sql]
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----
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NVL ( expression<1>, expression<2> )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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*Output*: 2nd expression if 1st expression is null, otherwise 1st expression.
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.Description
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Variant of <<sql-functions-conditional-coalesce>> with only two arguments.
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Returns the first of its arguments that is not null.
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If all arguments are null, then it returns `null`.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[nvlReturnFirst]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[nvlReturnSecond]
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----
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[[sql-functions-conditional-nullif]]
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==== `NULLIF`
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.Synopsis
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[source, sql]
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----
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NULLIF ( expression<1>, expression<2> )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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*Output*: `null` if the 2 expressions are equal, otherwise the 1st expression.
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.Description
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Returns `null` when the two input expressions are equal and
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if not, it returns the 1st expression.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[nullIfReturnFirst]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[nullIfReturnNull]
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----
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[[sql-functions-conditional-greatest]]
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==== `GREATEST`
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.Synopsis
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[source, sql]
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----
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GREATEST ( expression<1>, expression<2>, ... )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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...
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**N**th expression
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GREATEST can take an arbitrary number of arguments and
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all of them must be of the same data type.
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*Output*: one of the expressions or `null`
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.Description
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Returns the argument that has the largest value which is not null.
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If all arguments are null, then it returns `null`.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[greatestReturnNonNull]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[greatestReturnNull]
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----
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[[sql-functions-conditional-least]]
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==== `LEAST`
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.Synopsis
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[source, sql]
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----
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LEAST ( expression<1>, expression<2>, ... )
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----
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*Input*:
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<1> 1st expression
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<2> 2nd expression
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...
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**N**th expression
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LEAST can take an arbitrary number of arguments and
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all of them must be of the same data type.
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*Output*: one of the expressions or `null`
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.Description
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Returns the argument that has the smallest value which is not null.
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If all arguments are null, then it returns `null`.
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[leastReturnNonNull]
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----
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["source","sql",subs="attributes,callouts,macros"]
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----
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include-tagged::{sql-specs}/docs.csv-spec[leastReturnNull]
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----
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