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Selection Functions
Selection functions are a form of aggregate function operating on grouped data. They select a sub-set of the child values.
See Also
Aggregate functions joining() and distinct() that work in a similar way to these selection functions.
Any
Selects the first value found in the group that is not null() or err().
If no explicit ordering is set then the value selected is indeterminate.
any(${val})
Examples
any(${val})
${val} = [10, 20, 30, 40]
> 10
Bottom
Selects the bottom N values and returns them as a delimited string in the order they are read.
bottom(${val}, delimiter, limit)
Example
bottom(${val}, ', ', 2)
${val} = [10, 20, 30, 40]
> '30, 40'
First
Selects the first value found in the group even if it is null() or err().
If no explicit ordering is set then the value selected is indeterminate.
first(${val})
Example
first(${val})
${val} = [10, 20, 30, 40]
> 10
Last
Selects the last value found in the group even if it is null() or err().
If no explicit ordering is set then the value selected is indeterminate.
last(${val})
Example
last(${val})
${val} = [10, 20, 30, 40]
> 40
Nth
Selects the Nth value in a set of grouped values. If there is no explicit ordering on the field selected then the value returned is indeterminate.
nth(${val}, position)
Example
nth(${val}, 2)
${val} = [20, 40, 30, 10]
> 40
Top
Selects the top N values and returns them as a delimited string in the order they are read.
top(${val}, delimiter, limit)
Example
top(${val}, ', ', 2)
${val} = [10, 20, 30, 40]
> '10, 20'