hasprefix operator
Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer ✅ Azure Monitor ✅ Microsoft Sentinel
Filters a record set for data with a case-insensitive starting string.
For best performance, use strings of three characters or more. hasprefix 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 compares the hasprefix 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) |
|---|---|---|---|
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" |
For more information about other operators and to determine which operator is most appropriate for your query, see datatype string operators.
Performance tips
Note
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 hasprefix_cs.
Syntax
T | where Column hasprefix (Expression)
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| T | string |
✔️ | The tabular input whose records are to be filtered. |
| Column | string |
✔️ | The column used to filter. |
| Expression | string |
✔️ | The expression for which to search. |
Returns
Rows in T for which the predicate is true.
Example
StormEvents
| summarize event_count=count() by State
| where State hasprefix "la"
| project State, event_count
| State | event_count |
|---|---|
| LAKE MICHIGAN | 182 |
| LAKE HURON | 63 |
| LAKE SUPERIOR | 34 |
| LAKE ST CLAIR | 32 |
| LAKE ERIE | 27 |
| LAKE ONTARIO | 8 |