Allow to check the length of an array without having to store it into a variable

[thorsten.langner]

@sebme for this use case (to only find if the array length is only 1) you can use the workaround I mentioned here:

@thorsten.langner

Update:
using TOTEXT(…) is more secure, because you can search for "," then (a simple comma in the value is no longer an issue)

Context for the update:
TOTEXT(@Table Aggregation.Aggr_Test) output is like so:

["j4gmt7PjnBu23s5R7","cjAMazfQowczQNMEsmx589fTgtoSu2RQjk"]

while @Table Aggregation.Aggr_Test + '' outputs something like this:

j4gmt7PjnBu23s5R7,cjAMazfQowczQNMEsmx589fTgtoSu2RQjk

Not a beauty in readability, but it works in most cases…