问题
Is there any way to obtain a table with key/value pairs from a CLOB Json Column?
The idea here is to get these values, on a dynamic way. Because the CLOB column does not always contain the same structure.
I've created a function that does this, however since it literally parses the json string, when we use it in a table with many records its very slow. And by very slow I mean like 2-5 records per second, i know it's terrible.
The Oracle tools (v.12c) do not provide a dynamic way to obtain the json tags/values, we have always to specify the paths.
I've been digging all around without any luck. Any thoughts?
回答1:
12.2 contains a set of PL/SQL objects that can be used to build a DOM like structure of a JSON document. You can then extract key lists etc using methods on the objects. Look in the 12.2 doc for JSON_OBJECT_T, JSON_ARRAY_T etc which can be used like this..
SQL> create or replace type NV_PAIR_T as object (
2 NAME VARCHAR2(32),
3 VALUE VARCHAR2(32)
4 )
5 /
Type created.
SQL> create or replace type NV_PAIR_TABLE as TABLE of NV_PAIR_T
2 /
Type created.
SQL> create or replace function GET_KEY_VALUES(P_JSON_DOC VARCHAR2)
2 return NV_PAIR_TABLE PIPELINED
3 as
4 JO JSON_OBJECT_T := JSON_OBJECT_T(P_JSON_DOC);
5 JO_KEYS JSON_KEY_LIST := JO.get_keys();
6 begin
7
8 for i in 1..JO_KEYS.count loop
9 pipe row (NV_PAIR_T(JO_KEYS(i),JO.get_string(JO_KEYS(i))));
10 end loop;
11 end;
12 /
Function created.
SQL> select *
2 from TABLE(GET_KEY_VALUES('{"A":"AA", "B":"BB", "C":"CC"}'))
3 /
A AA
B BB
C CC
SQL>
Does this help
回答2:
Here's a variant that will walk a nested structure.
SQL> drop FUNCTION PROCESS_JSON_DOCUMENT
2 /
Function dropped.
SQL> drop TYPE NV_PAIR_TABLE
2 /
Type dropped.
SQL> drop TYPE NV_PAIR_T
2 /
Type dropped.
SQL> create or replace TYPE NV_PAIR_T as object (
2 JSON_PATH VARCHAR2(4000),
3 VALUE VARCHAR2(4000)
4 )
5 /
Type created.
SQL> create or replace TYPE NV_PAIR_TABLE
2 as TABLE of NV_PAIR_T
3 /
Type created.
SQL> create or replace FUNCTION PROCESS_JSON_DOCUMENT(P_JSON_PATH VARCHAR2, P_JSON_DOCUMENT VARCHAR2)
2 return NV_PAIR_TABLE PIPELINED
3 as
4 V_JSON_OBJECT JSON_OBJECT_T := JSON_OBJECT_T(P_JSON_DOCUMENT);
5 V_KEY_LIST JSON_KEY_LIST := V_JSON_OBJECT.get_keys();
6 V_KEY_NAME VARCHAR2(4000);
7 V_JSON_PATH VARCHAR2(4000);
8 V_CHILD_DOCUMENT VARCHAR2(4000);
9 begin
10 for i in 1..V_KEY_LIST.count loop
11 V_KEY_NAME := V_KEY_LIST(i);
12 if (V_JSON_OBJECT.get_type(V_KEY_LIST(i)) <> 'OBJECT') then
13 pipe row (NV_PAIR_T(P_JSON_PATH || '.' || V_KEY_NAME,V_JSON_OBJECT.get_string(V_KEY_NAME)));
14 else
15 V_JSON_PATH := P_JSON_PATH || '.' || V_KEY_NAME;
16 V_CHILD_DOCUMENT := V_JSON_OBJECT.get_object(V_KEY_NAME).to_string();
17 for j in (select * from TABLE(PROCESS_JSON_DOCUMENT(V_JSON_PATH, V_CHILD_DOCUMENT))) loop
18 pipe row (NV_PAIR_T(J.JSON_PATH,J.VALUE));
19 end loop;
20 end if;
21 end loop;
22 end;
23 /
Function created.
SQL> column JSON_PATH format A32
SQL> column VALUE format A32
SQL> select *
2 from TABLE(PROCESS_JSON_DOCUMENT('$','{"A":"AA", "B":"BB", "C":"CC", "X" : {"A":"AA", "B":"BB", "C":"CC"}}'))
3 /
$.A AA
$.B BB
$.C CC
$.X.A AA
$.X.B BB
$.X.C CC
6 rows selected.
SQL>
来源：https://stackoverflow.com/questions/42702150/oracle-json-to-key-value-pair-table