BSON_VALUE_VARCHAR function

The BSON_VALUE_VARCHAR function is a built-in SQL function that converts character strings whose size is fewer than 255 bytes in a BSON field to a VARCHAR data type. The function returns string values.

Use the BSON_VALUE_VARCHAR function to return or operate on character data in a field in a BSON column with SQL statements.

Syntax

BSON_VALUE_VARCHAR function

>>-BSON_VALUE_VARCHAR--(--bson_column--,--"--field--"--)-------><


Element	Description	Restrictions	Syntax
`bson_column`	Name of a BSON column	Must exist	Identifier
`field`	A string that represents a field name to search for in the BSON column. Can be a multilevel identifier.		Quoted String, Column Expressions

Usage

The field parameter can be a simple SQL identifier. The statements in the following example create a table with a BSON column, insert three documents, and then return the value of the name field. The documents are explicitly cast to JSON and then implicitly cast to BSON.

CREATE DATABASE testdb WITH LOG;
CREATE TABLE IF NOT EXISTS bson_table(bson_col BSON);

INSERT INTO bson_table VALUES('{id:100,name:"Joe"}'::JSON);
INSERT INTO bson_table VALUES('{id:101,name:"Mike"}'::JSON);
INSERT INTO bson_table VALUES('{id:102,name:"Nick"}'::JSON);

SELECT BSON_VALUE_VARCHAR(bson_col,"name") FROM bson_table;

     (expression)   
             Joe
             Mike
             Nick

3 row(s) retrieved.

This example shows simple field-name value pairs, but the field parameter in BSON_VALUE_VARCHAR expressions for BSON columns with more complex structures can be specified as a multilevel identifier in dot notation.