startswith operator

Filters a record set for data with a case-insensitive string starting sequence.

The following table compares the startswith operators using the abbreviations provided:

  • RHS = right-hand side of the expression
  • LHS = left-hand side of the expression
Operator Description Case-Sensitive Example (yields true)
startswith RHS is an initial subsequence of LHS No "Fabrikam" startswith "fab"
!startswith RHS isn't an initial subsequence of LHS No "Fabrikam" !startswith "kam"
startswith_cs RHS is an initial subsequence of LHS Yes "Fabrikam" startswith_cs "Fab"
!startswith_cs RHS isn't an initial subsequence of LHS Yes "Fabrikam" !startswith_cs "fab"

For more information about other operators and to determine which operator is most appropriate for your query, see datatype string operators.

Performance tips


Performance depends on the type of search and the structure of the data. For best practices, see Query best practices.

When possible, use the case-sensitive startswith_cs.


T | where col startswith (expression)

Learn more about syntax conventions.


Name Type Required Description
T string The tabular input to filter.
col string The column used to filter.
expression string The expression by which to filter.


Rows in T for which the predicate is true.


| summarize event_count=count() by State
| where State startswith "Lo"
| where event_count > 10
| project State, event_count


State event_count