Type Conversion/Type coercions¶
Converting an expression of a given type to another type is known as type conversion.
Legacy version compatibility¶
- nGQL 1.0 adopts the
C-style of type conversion (implicitly or explicitly):(type_name)expression. For example, the results ofYIELD (int)(TRUE)is1. But it is error-prone to users who are not familiar with the C language.
- since nGQL 2.0, the openCypher way of type coercions is adopted.
Type coercions functions¶
| Function | Description |
|---|---|
| toBoolean() | Converts a string value to a boolean value. |
| toFloat() | Converts an integer or string value to a floating point number. |
| toInteger() | Converts a floating point or string value to an integer value. |
| type() | Returns the string representation of the relationship type. |
Examples¶
```ngql nebula> UNWIND [true, false, 'true', 'false', NULL] AS b \ RETURN toBoolean(b) AS b; +----------+ | b | +----------+ | true | | false | | true | | false | | NULL | +----------+
nebula> RETURN toFloat(1), toFloat('1.3'), toFloat('1e3'), toFloat('not a number'); +------------+----------------+----------------+-------------------------+ | toFloat(1) | toFloat("1.3") | toFloat("1e3") | toFloat("not a number") | +------------+----------------+----------------+-------------------------+ | 1.0 | 1.3 | 1000.0 | NULL | +------------+----------------+----------------+-------------------------+
nebula> RETURN toInteger(1), toInteger('1'), toInteger('1e3'), toInteger('not a number'); +--------------+----------------+------------------+---------------------------+ | toInteger(1) | toInteger("1") | toInteger("1e3") | toInteger("not a number") | +--------------+----------------+------------------+---------------------------+ | 1 | 1 | 1000 | NULL | +--------------+----------------+------------------+---------------------------+
nebula> MATCH (a:player)-[e]-() \ RETURN type(e); +----------+ | type(e) | +----------+ | "follow" | | "follow" | +----------+
nebula> MATCH (a:player {name: "Tim Duncan"}) \ WHERE toInteger(right(id(a),3)) == 100 \ RETURN a; +----------------------------------------------------+ | a | +----------------------------------------------------+ | ("player100" :player{age: 42, name: "Tim Duncan"}) | +----------------------------------------------------+
nebula> MATCH (n:player) \ WITH n LIMIT toInteger(ceil(1.8)) \ RETURN count(*) AS count; +-------+ | count | +-------+ | 2 | +-------+ ```