elasticsearch/docs/reference/query-languages/esql/esql-implicit-casting.md

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Implicit casting	https://www.elastic.co/guide/en/elasticsearch/reference/current/esql-implicit-casting.html

{{esql}} implicit casting [esql-implicit-casting]

Often users will input date, date_period, time_duration, ip or version as simple strings in their queries for use in predicates, functions, or expressions. {{esql}} provides type conversion functions to explicitly convert these strings into the desired data types.

Without implicit casting users must explicitly code these to_X functions in their queries, when string literals don’t match the target data types they are assigned or compared to. Here is an example of using to_datetime to explicitly perform a data type conversion.

FROM employees
| EVAL dd_ns1=date_diff("day", to_datetime("2023-12-02T11:00:00.00Z"), birth_date)
| SORT emp_no
| KEEP dd_ns1
| LIMIT 1

Implicit casting example [esql-implicit-casting-example]

Implicit casting automatically converts string literals to the target data type. This allows users to specify string values for types like date, date_period, time_duration, ip and version in their queries.

The first query can be coded without calling the to_datetime function, as follows:

FROM employees
| EVAL dd_ns1=date_diff("day", "2023-12-02T11:00:00.00Z", birth_date)
| SORT emp_no
| KEEP dd_ns1
| LIMIT 1

Operations that support implicit casting [esql-implicit-casting-supported-operations]

The following table details which {{esql}} operations support implicit casting for different data types.

	ScalarFunctions	Operators	GroupingFunctions	AggregateFunctions
DATE	Y	Y	Y	N
DATE_PERIOD/TIME_DURATION	Y	N	Y	N
IP	Y	Y	Y	N
VERSION	Y	Y	Y	N
BOOLEAN	Y	Y	Y	N

ScalarFunctions includes:

• Conditional Functions and Expressions
• Date and Time Functions
• IP Functions

Operators includes:

• Binary Operators
• Unary Operator
• IN