hasprefix operator

Filters a record set for data with a case-insensitive starting string. has searches for indexed terms, where a term is three or more characters. If your term is fewer than three characters, the query scans the values in the column, which is slower than looking up the term in the term index.

The following table provides a comparison of the hasprefix operators:

Operator Description Case-Sensitive Example (yields true)
hasprefix RHS is a term prefix in LHS No "North America" hasprefix "ame"
!hasprefix RHS isn't a term prefix in LHS No "North America" !hasprefix "mer"
hasprefix_cs RHS is a term prefix in LHS Yes "North America" hasprefix_cs "Ame"
!hasprefix_cs RHS isn't a term prefix in LHS Yes "North America" !hasprefix_cs "CA"

Note

The following abbreviations are used in the table above:

  • RHS = right hand side of the expression
  • LHS = left hand side of the expression

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

Case-insensitive operators are currently supported only for ASCII-text. For non-ASCII comparison, use the tolower() function.

Performance tips

Note

Performance depends on the type of search and the structure of the data.

For faster results, use the case-sensitive version of an operator, for example, hasprefix_cs, not hasprefix. For best practices, see Query best practices.

Syntax

T | where Column hasprefix (Expression)

Arguments

  • T - The tabular input whose records are to be filtered.
  • Column - The column to filter.
  • Expression - Scalar or literal expression.

Returns

Rows in T for which the predicate is true.

Examples

Use hasprefix operator

StormEvents
    | summarize event_count=count() by State
    | where State hasprefix "la"
    | project State, event_count

Output

State event_count
LAKE MICHIGAN 182
LAKE HURON 63
LAKE SUPERIOR 34
LAKE ST CLAIR 32
LAKE ERIE 27
LAKE ONTARIO 8