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#### 6.1.18 `group`

Usage:

       group [-[no]parallel] <key> [<key> ...] [<aggcol> ...]

Calculates aggregate functions on groups of rows. This does the same job as a `SELECT ... GROUP BY` statement with aggregate functions in ADQL/SQL.

The functionality is identical to that of the `tgroup` command, and the meaning and syntax of the `<key>` and `<aggcol>` words are identical too, except that the `<aggcol>` delimiter character is an at sign ("`@`") rather than a semicolon ("`;`"), so a group entry count can be added for instance using an `<aggcol>` like "`null@count`". The `<aggcol>` arguments are distinguished by the fact that they contain at least one delimiter ("`@`"). See the `tgroup` documentation for a full explanation of the syntax and functionality.

The syntax here is rather cramped, so in many cases it will be more comfortable to use `tgroup` instead, but this filter is provided for cases where that may be more convenient.

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STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk