Materialize/doc/user/content/transform-data/idiomatic-materialize-sql/mz_now.md

---

title: "mz_now() expressions" description: " mz_now() expressions can only take comparison operators. mz_now() expressions cannot be used with disjunctions OR in view definitions." menu: main:

parent: idiomatic-materialize-sql
identifier: idiomatic-materialize-mz_now
weight: 45

---

Overview

In Materialize, mz_now() function returns Materialize's current virtual timestamp (i.e., returns mz_timestamp). The function can be used in temporal filters to reduce the working dataset.

mz_now() expression has the following form:

mz_now() <comparison_operator> <numeric_expr | timestamp_expr>

Idiomatic Materialize SQL

mz_now() expressions to calculate past or future timestamp

Idiomatic Materialize SQL: {{< include-md file="shared-content/mz_now_operators.md" >}}

Examples

{{< yaml-table data="mz_now/mz_now_operators" noHeader="true" >}}

Disjunctions (OR)

{{< include-md file="shared-content/mz_now_clause_disjunction_restrictions.md"

}}

For example:

{{< yaml-table data="mz_now/mz_now_combination" >}}

Idiomatic Materialize SQL: When mz_now() is included in a materialized view definition, a view definition that is being indexed, or a SUBSCRIBE statement, instead of using disjunctions (OR) when using mz_now(), rewrite the query to use UNION ALL or UNION instead, deduplicating as necessary:

• In some cases, you may need to modify the conditions to deduplicate results when using UNION ALL. For example, you might add the negation of one input's condition to the other as a conjunction.

• In some cases, using UNION instead of UNION ALL may suffice if the inputs do not contain other duplicates that need to be retained.

Examples

{{< yaml-table data="mz_now/mz_now_disjunction_alternatives" noHeader="true" >}}