<a id="ksqldb-reference-define"></a>

# DEFINE statement in ksqlDB for Confluent Platform

## Synopsis

```sql
DEFINE <name> = '<value>';
```

Where:

```none
<name>  is the variable name
<value> is the variable value
```

## Description

Defines a variable to be used within SQL statements. Reference the
variable with `${variable}` syntax.

Valid variable names start with a letter or underscore and are followed
by zero or more alphanumeric characters or underscores.

All variable values must be enclosed into single-quotes. Single-quotes
are removed during variable substitution. To escape single-quotes,
enclose the value with triple-quotes.

There is no type declaration for a value.

Use the [SHOW VARIABLES](show-variables.md#ksqldb-reference-show-variables)
statement to see all variable definitions.

Use the [UNDEFINE](undefine.md#ksqldb-reference-undefine)
statement to clear a variable definitions.

## Example

```sql
DEFINE replicas = '3';
DEFINE format = 'JSON';
DEFINE name = 'Tom Sawyer';
DEFINE topicName = '''my_topic'''; -- becomes 'my_topic'
```