{ "date": "2014-12-15T13:50:00", "slug": "oracle-lateral-inline-view-cursor-expression-and-12c-implicit-statement-result", "link": "https://www.dbi-services.com/blog/oracle-lateral-inline-view-cursor-expression-and-12c-implicit-statement-result/", "title": { "rendered": "Oracle lateral inline view, cursor expression and 12c implicit statement result" }, "content": { "rendered": "

By Franck Pachot

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\nI’ll present here 3 ways to run a query for each result of another query. Let’s take an exemple: get all executions plan (select from dbms_xplan.display_cursor) for each of my queries (identified from v$sql). The 90’s way was to run the first query, which generates the second queries into a spool file, and execute that file. Here are easier ways, some of them coming from 12c new features lateral join and implicit statement result.

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Test case

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I’m running 2 queries and will identify them from their module (APPINFO from sqlplus) and user:

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SQL> connect scott/tiger\nConnected.\n\nSQL> set appinfo DEMO\n\nSQL> select * from DEPT;\nSQL> select * from EMP;\n
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I don’t show the result – you know it – but here is how I identify the queries:

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SQL> select sql_id,child_number,sql_text from v$sql where plan_hash_value>0 and module='DEMO' and parsing_schema_name='SCOTT';\n\nSQL_ID        CHILD_NUMBER SQL_TEXT\n------------- ------------ ------------------------------\n5aht0fch310ca            0 select * from EMP\n18wrqtcj3ksap            0 select * from DEPT\n
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And I want to run dbms_xplan.display_cursor(sql_id,child_number) for each of them. Here are 3 ways to do it

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Cursor expression

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Do you know cursor expressions? In your SELECT expressions, you can have a query. Your client will retrieve it as a cursor and have to run it. sqlplus and sqldeveloper does that. Here is an example:

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SQL> select\n  cursor (select * from table(dbms_xplan.display_cursor(sql_id,child_number,format=>'TYPICAL'))) PLAN\n  from\n  (select * from v$sql where plan_hash_value>0 and module='DEMO' and parsing_schema_name='SCOTT')\n /\n\n
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which gives the following result:

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PLAN\n--------------------\nCURSOR STATEMENT : 1\n\nPLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------------\nSQL_ID  5aht0fch310ca, child number 0\n-------------------------------------\nselect * from EMP\n\nPlan hash value: 3956160932\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\n13 rows selected.\n\nCURSOR STATEMENT : 1\n\nPLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------------\nSQL_ID  18wrqtcj3ksap, child number 0\n-------------------------------------\nselect * from DEPT\n\nPlan hash value: 3383998547\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| DEPT |     4 |    80 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\n13 rows selected.\n\n
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This is possible on all versions, and the output can change depending on the tool you use. sqlplus handles it as above, running each cursor.

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implicit statement result

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You want to do it from pl/sql? That’s possible. But you have to format the output yourself with dbms_output.

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Except if you are in 12c and use the ‘implicit statement result’ new feature:

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SQL> declare\n  r sys_refcursor;\n begin\n  for c in\n  (select * from v$sql where plan_hash_value>0 and module='DEMO' and parsing_schema_name='SCOTT')\n  loop\n   open r for select * from table(dbms_xplan.display_cursor(c.sql_id,c.child_number));\n   dbms_sql.return_result(r);\n  end loop;\n end;\n /\nPL/SQL procedure successfully completed.\n
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which gives the following result:

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ResultSet #1\n\nPLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------------\nSQL_ID  5aht0fch310ca, child number 0\n-------------------------------------\nselect * from EMP\n\nPlan hash value: 3956160932\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\n13 rows selected.\n\nResultSet #2\n\nPLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------------\nSQL_ID  18wrqtcj3ksap, child number 0\n-------------------------------------\nselect * from DEPT\n\nPlan hash value: 3383998547\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| DEPT |     4 |    80 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\n13 rows selected.\n\n
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This is similar to the previous approach in the way that the client has to manage the result.

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Lateral inline view

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This is my preferred way which is only SQL and do not depend on the client formatting. A lateral inline view is a subquery that you put in the FROM clause, using the LATERAL keyword, and which can use data from the other tables on the left of it in the FROM clause:

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SQL> select plan_table_output from\n  (select * from v$sql where plan_hash_value>0 and module='DEMO' and parsing_schema_name='SCOTT'),\n  lateral (select * from table(dbms_xplan.display_cursor(sql_id,child_number)))\n ;\n
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which gives the following result:

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PLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------------\nSQL_ID  5aht0fch310ca, child number 0\n-------------------------------------\nselect * from EMP\n\nPlan hash value: 3956160932\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\nSQL_ID  18wrqtcj3ksap, child number 0\n-------------------------------------\nselect * from DEPT\n\nPlan hash value: 3383998547\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| DEPT |     4 |    80 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\n
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This is a 12c new feature. It existed on previous versions but not enabled by default and not documented, but you can set it with the following event:

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SQL> host oerr ora 22829\n\nSQL> alter session set events '22829 trace name context forever';\n
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12c came with a lot of nice improvement in SQL and PL/SQL and they are available in all editions.

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Update

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What is very cool about twitter is that sometimes I have to update my blog post as soon as it is published. In that case it seems that I ignored the simplest way to do that since 9i:

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@FranckPachot Why not just “from v$sql, table(dbms_xplan.display_cursor(…))”? Left correlation is official and it works since 9i

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— Vladimir Sitnikov (@VladimirSitnikv) December 14, 2014

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So here it is:

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SQL> select plan_table_output from\n  2   v$sql,\n  3   table(dbms_xplan.display_cursor(sql_id,child_number))\n  4  where plan_hash_value>0 and module='DEMO' and parsing_schema_name='SCOTT'\n  5  ;\n\nPLAN_TABLE_OUTPUT\n------------------------------------------------------------------------------------------\nSQL_ID  5aht0fch310ca, child number 0\n-------------------------------------\nselect * from EMP\n\nPlan hash value: 3956160932\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\nSQL_ID  18wrqtcj3ksap, child number 0\n-------------------------------------\nselect * from DEPT\n\nPlan hash value: 3383998547\n\n--------------------------------------------------------------------------\n| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |\n--------------------------------------------------------------------------\n|   0 | SELECT STATEMENT  |      |       |       |     3 (100)|          |\n|   1 |  TABLE ACCESS FULL| DEPT |     4 |    80 |     3   (0)| 00:00:01 |\n--------------------------------------------------------------------------\n\n\n26 rows selected.\n\n
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That does not invalidate this blog post because I wanted to show those 3 features. It’s just my example which was badly chosen because dbms_xplan returns a table expression and left correlation can be used for it.

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Thanks to Vladimir Sitnikov, I learned a 9i feature while blogging about 12c new feature 🙂

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