WQL (SQL for WMI)
The WMI Query Language (WQL) is a subset of the American National Standards Institute Structured Query Language (ANSI SQL) with minor semantic changes. The following table lists the WQL keywords.
| WQL keyword | Meaning |
|---|---|
| AND |
Combines two Boolean expressions, and returns TRUE when both expressions are TRUE. |
| ASSOCIATORS OF | Retrieves all instances that are associated with a source instance. Use this statement with schema queries and data queries. |
| __CLASS | References the class of the object in a query. |
| FROM |
Specifies the class that contains the properties listed in a SELECT statement. Windows Management Instrumentation (WMI) supports data queries from only one class at a time. |
| GROUP Clause | Causes WMI to generate one notification to represent a group of events. Use this clause with event queries. |
| HAVING | Filters the events that are received during the grouping interval that is specified in the WITHIN clause. |
| IS | Comparison operator used with NOT and NULL. The syntax for this statement is the following: IS [NOT] NULL (where NOT is optional) |
| ISA | Operator that applies a query to the subclasses of a specified class. For more information, see ISA Operator for Event Queries, ISA Operator for Data Queries, and ISA Operator for Schema Queries. |
| KEYSONLY |
Used in REFERENCES OF and ASSOCIATORS OF queries to ensure that the resulting instances are only populated with the keys of the instances, which reduces the overhead of the call. |
| LIKE | Operator that determines whether or not a given character string matches a specified pattern. |
| NOT |
Comparison operator that use in a WQL SELECT query, for example: |
| NULL | Indicates an object does not have an explicitly assigned value. NULL is not equivalent to zero (0) or blank. |
| OR |
Combines two conditions. When more than one logical operator is used in a statement, the OR operators are evaluated after the AND operators. |
| REFERENCES OF | Retrieves all association instances that refer to a specific source instance. Use this statement with schema and data queries. The REFERENCES OF statement is similar to the ASSOCIATORS OF statement. However, it does not retrieve endpoint instances; it retrieves the association instances. |
| SELECT |
Specifies the properties that are used in a query. For more information, see SELECT Statement for Data Queries, SELECT Statement for Event Queries, or SELECT Statement for Schema Queries. |
| TRUE | Boolean operator that evaluates to -1 (minus one). |
| WHERE | Narrows the scope of a data, event, or schema query. |
| WITHIN | Specifies a polling or grouping interval. Use this clause with event queries. |
| FALSE |
Boolean operator that evaluates to 0 (zero). |
Note
Using a WQL key word as an object name can result in a query that cannot be parsed even when the query compiles without error.