For the document in Example 4-2 the phone types are "Office" and "Mobile", and the array returned is either or. For each document it returns a VARCHAR2 value whose contents represent a JSON array with elements the phone types, in an unspecified order.
The error clause for json_query can specify EMPTY ON ERROR, which means that an empty array ( ) is returned in case of error (no error is raised).Įxample 16-1 shows an example of the use of SQL/JSON function json_query with an array wrapper. The wrapper clause determines the form of the returned string value. Keywords FORMAT JSON are not needed (or available) for json_query - JSON formatting is implicit for the return value. For example, an ASCII TAB character (Unicode character CHARACTER TABULATION, U+0009) is escaped as \t. This includes ensuring that non-ASCII characters in string values are escaped as needed. ( VARCHAR2 is the default.) The value returned always contains well-formed JSON data. A BLOB result is in the A元2UTF8 character set. In the RETURNING clause you can specify data type VARCHAR2, CLOB, or BLOB. The path expression can target any number of JSON values. The second argument to json_query is a SQL/JSON path expression followed by optional clauses RETURNING, WRAPPER, ON ERROR, and ON EMPTY.
The result of evaluating the SQL expression is used as the context item for evaluating the path expression. It can be a table or view column value, a PL/SQL variable, or a bind variable with proper casting. It can be of data type VARCHAR2, CLOB, or BLOB. The first argument to json_query is a SQL expression that returns an instance of a scalar SQL data type (that is, not an object or collection data type).
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