MySQL提供了一些功能强大的JSON函数，其中两个关键的函数是JSON_ARRAYAGG和JSON_OBJECT。本文将深入探讨这...
如果所有的string-expr值为NULL, JSON_ARRAYAGG返回一个空的JSON数组[]。
insert into test_tbl values('val1', 'val9', 'val10', 'val7'); 使用以下查询创建Json时: SELECT JSON_OBJECT ( 'output' VALUE JSON_ARRAYAGG(JSON_OBJECT('common' VALUE test_col1, 'list' VALUE JSON_ARRAYAGG(JSON_OBJECT('key1' VALUE test_col2, 'key2' VALUE test_col3))) ) FROM ...
JSON_ARRAYAGG将默认返回VARCHAR2，而VARCHAR2限制为4000个字符，因此您可以：
“Not quite,” replies Mark. Another function—JSON_ARRAYAGG—can aggregate multiple tables.Listing 1shows how the aggregation function can create nested JSON documents. Listing 1.Nested JSON documents Copy Copied to Clipboard Error: Could not Copy ...
If the data exceeds the limit, calls toJSON_OBJECT,JSON_OBJECTAGG,JSON_ARRAYAGG, andJSON_TRANSFORMwill fail at runtime with the following exception: select json_object( 'name-is-twenty-chars' : rpad('x',3974,'x') ) from dual;
您不需要apex_json,这可以直接用sql完成。这里是EMP表上的一个示例。 SELECT JSON_OBJECT ( KEY 'success' VALUE 'true', KEY 'employees' VALUE ( SELECT JSON_ARRAYAGG( JSON_OBJECT ( KEY 'ename' VALUE e.ename, KEY 'empno' VALUE e.empno, KEY 'job' VALUE e.job ) ) FROM emp e ) ) AS...
unnest/array_aggYesYesYesYesYesYesYesYesYesYesYesYesYesNoNoNo Updateable cursorsYesYesYesYesYesYesYes...
Going from a relational representation back to JSON is similarly easy. All we do is add one (or more) JSON generation functions to a query. In the following we are generating an array of all city name. selectJSON_ArrayAgg(c.json_document.name) from cities c; ...
Special handling is needed, because I need to know the levels of the rows immediately preceding and following the row being processed. If a JSON object is a parent, I add a name / value pair where the value is an array. The name is by default ‘children’ but it is configurable by ...