DB_CALL_STRING
Syntax
DB_CALL_STRING( db_function_name [ , arg_1 [ , arg_2 [ , ... ] ] ] )
Description
Warning
The availability and behavior of native functions depends on your database type and version.
It is recommended to use native functions only if there is no supported DataLens function (composition of functions) that can achieve the required result.
Calls a native database function by its name. Native function should return a value of type String. The function is executed for every row in the dataset (non-aggregated).
The first argument db_function_name must be a constant string with the name of the database function to call. All subsequent arguments are passed to the native function in the same order as written in the formula and can be of any type, including types that are not currently supported by DataLens.
The function name must contain only alphanumeric characters, underscore and colon characters.
Argument types:
db_function_name—Stringarg_1—Anyarg_2—Any
Return type: String
Note
Only constant values are accepted for the arguments (db_function_name).
Examples
DB_CALL_STRING("dictGetStringOrDefault", "categories", "category_name", [category_id], "other") -- ClickHouse: read from dictionary with default value
DB_CALL_STRING("JSONExtractString", [json_field], "category", "last_order_date") -- ClickHouse: extract nested JSON attribute
DB_CALL_STRING("hex", DB_CALL_STRING("SHA1", [salt_param] + [some_id])) -- ClickHouse: calculate hash with salt
Data source support
ClickHouse 21.8, Microsoft SQL Server 2017 (14.0), MySQL 5.7, Oracle Database 12c (12.1), PostgreSQL 9.3, Trino, YDB.