Columns

Every table in Kusto, and every tabular data stream, is a rectangular grid of columns and rows. Every column in the table has a name and a specific scalar data type. The columns of a table or a tabular data stream are ordered, so a column also has a specific position in the table's collection of columns.

Notes

  • Column names are case-sensitive.
  • Column names follow the rules for entity names.
  • Maximum limit of columns per table is 10,000.

In queries, columns are generally references by name only. They can only appear in expressions, and the query operator under which the expression appears determines the table or tabular data stream, so the column's name need not be further scoped. For example, in the following query we have an unnamed tabular data stream (defined through the datatable operator that has a single column, c. The tabular data stream is then filtered by a predicate on the value of that column, producing a new unnamed tabular data stream with the same columns but fewer rows. The as operator then names the tabular data stream and its value is returned as the results of the query. Note in particular how the column c is referenced by name without a need to reference its container (indeed, that container has no name):

datatable (c:int) [int(-1), 0, 1, 2, 3]
| where c*c >= 2
| as Result

As is often common in the relational databases world, rows are sometimes called records and columns are sometimes called attributes.

Details on managing columns can be found under managing columns.