$where parameter allows you to filter your results using boolean operators. For example, to retrieve only quakes with a
magnitude of greater than 3.0:
You can also combine multiple filters together using boolean operators to chain filters together. If we also only wanted quakes from the
Multiple boolean operators are available to combine filters:
|The logical and of two expressions.
a AND b will return true ONLY if
b are both true.
|The logical or of two expressions.
a or b will return true if either
b are true.
|The logical not of an expression.
NOT a will return true, ONLY if a is false.
|Whether a value is null or not.
a IS NULL will return true, ONLY if
a is null.
IS NOT NULL
|Whether a values is not null.
a IS NOT NULL will return true, ONLY if
a is not null
( ... )
|Parentheses are used for defining order of operations.
b>3 AND (a=1 OR a=2)
Note that using simple filtering, equality clauses can be simplified. And since multiple parameters are implicitly
ANDed together, the above query can be simplified to:
Multiple equality clauses can be even simpler: