Oracle Analytic SQL NCOUG 2008 By: Ron Warshawsky CTO DBA InfoPower, Inc.

Oracle Analytic SQL Note: “standard” name is “Window” functions When? – Starting 8i Why? – Simple Solution of Complex Problems Why Exactly? – advanced ranking, aggregation, row comparison, statistics, “what if” scenarios Order of Evaluation in SQL: Prior to “ORDER BY” clause

Oracle Analytic SQL Syntax: Analytic-Function(,,...) OVER ( ) PARTITION BY – aggregates result set into groups ORDER BY – orders data within a partition WINDOWING – rows or ranges (logical offset)

Oracle Analytic SQL More Windowing: BETWEEN... AND UNBOUNDED PRECEDING – start of partition UNBOUNDED FOLLOWING – end of partition CURRENT ROW value_expr Examples: ROWS BETWEEN 1 PRECEDING and 1 FOLLOWING ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW RANGE BETWEEN INTERVAL '7' day PRECEDING AND CURRENT ROW

Oracle Analytic SQL Major Functions: STANDARD AGGREGATE FUNCTIONS ROW_NUMBER() LAG() LEAD() RANK() DENSE_RANK() PERCENT_RANK() NTILE() FIRST_VALUE() LAST_VALUE() FIRST() LAST() STATISTICAL FUNCTIONS

Oracle Analytic SQL Practical Examples

Oracle Analytic SQL Selecting the Top n Records select sql_id, BUFFER_GETS_DELTA from ( select sql_id, BUFFER_GETS_DELTA, dense_rank() over (order by BUFFER_GETS_DELTA desc) dr from DBA_HIST_SQLSTAT ) x where dr <= 5 ;

Oracle Analytic SQL Calculate 3 period Moving Average select snap_id,sql_id,BUFFER_GETS_DELTA,avg(BUFFER_GETS_DELTA) over (order by snap_id rows between 1 preceding and 1 following ) MA_3snap_BG from DBA_HIST_SQLSTAT where sql_id = '0h6b2sajwb74n' ;

Oracle Analytic SQL Calculate 3 Day Moving Average select BEGIN_INTERVAL_TIME,sql_id,BUFFER_GETS_DELTA,avg(BUFFER_GETS_DELTA) over ( order by BEGIN_INTERVAL_TIME RANGE between interval '1' day preceding and interval '1' day following ) MA_3day_BG from DBA_HIST_SQLSTAT a,dba_hist_snapshot b where a.INSTANCE_NUMBER = b.INSTANCE_NUMBER and a.SNAP_ID = b.SNAP_ID and sql_id = '0h6b2sajwb74n' ;

Oracle Analytic SQL Sort Set by Most Frequently Occurring Items select sql_id, CNT, dense_rank() over (order by cnt desc) as rnk from ( select sql_id,count(*) as cnt from DBA_HIST_SQLSTAT group by sql_id ) x

Oracle Analytic SQL Identify Percentage of Total select distinct sql_id, (sql_bg/total)*100 as pct from ( select sql_id, sum(BUFFER_GETS_DELTA) over () total, sum(BUFFER_GETS_DELTA) over (partition by sql_id) sql_bg from DBA_HIST_SQLSTAT ) x order by 2 ;

Oracle Analytic SQL Reduce Skewing (ignore highest and lowest value within a set) select sql_id, avg(BUFFER_GETS_DELTA ) avg_bg from ( select sql_id, BUFFER_GETS_DELTA, min(BUFFER_GETS_DELTA) over (partition by sql_id) min_bg, max(BUFFER_GETS_DELTA) over (partition by sql_id) max_bg from DBA_HIST_SQLSTAT ) x where BUFFER_GETS_DELTA not in (min_bg, max_bg) group by sql_id ;

Oracle Analytic SQL Convert Rows into Columns select max(case when object_type='TABLE‘ then object_name else null end) as TAB_NAME, max(case when object_type='INDEX‘ then object_name else null end) as IDX_NAME from ( select object_type,object_name,row_number() over (partition by object_type order by object_name) rn from dba_objects where object_type in ('TABLE', 'INDEX' ) ) x group by rn order by 1 ;

Oracle Analytic SQL Create fix size “buckets” of data select segment_name ceil(row_number() over (order by segment_name)/50) grp, from DBA_SEGMENTS ;

Oracle Analytic SQL Create pre-defined number of data “buckets” select ntile(10) over (order by segment_name) grp, segment_name from DBA_SEGMENTS ;

Oracle Analytic SQL Mix Aggregates from multiple groups select sql_id, module, sum(BUFFER_GETS_DELTA ) over(partition by module) module_cnt, PARSING_SCHEMA_NAME, sum(BUFFER_GETS_DELTA ) over(partition by PARSING_SCHEMA_NAME) PARSING_SCHEMA_NAME_cnt, sum(BUFFER_GETS_DELTA ) over() total from DBA_HIST_SQLSTAT ;

Oracle Analytic SQL Aggregating across moving historical ranges select distinct x.* from ( select trunc(BEGIN_INTERVAL_TIME ) SNAP_Date,sum(BUFFER_GETS_DELTA) over (partition by trunc(BEGIN_INTERVAL_TIME ) ) snap_bg,sum(BUFFER_GETS_DELTA ) over(order by trunc(BEGIN_INTERVAL_TIME ) range between 14 preceding and current row) prior_2week_bg from DBA_HIST_SQLSTAT a,dba_hist_snapshot b where a.INSTANCE_NUMBER = b.INSTANCE_NUMBER and a.SNAP_ID = b.SNAP_ID ) x ;

Oracle Analytic SQL Identify Consecutive Ranges of Time select a.sql_id, b.BEGIN_INTERVAL_TIME snap_time, lead(b.BEGIN_INTERVAL_TIME) over (order by a.snap_id) next_snap_time from DBA_HIST_SQLSTAT a,dba_hist_snapshot b where a.INSTANCE_NUMBER = b.INSTANCE_NUMBER and a.SNAP_ID = b.SNAP_ID and sql_id = '83taa7kaw59c1'

Oracle Analytic SQL Access Future and Historical rows select snap_id,BUFFER_GETS_DELTA,nvl(lead(BUFFER_GETS_DELTA) over (order by snap_id, BUFFER_GETS_DELTA ), null ) forward,nvl(lag (BUFFER_GETS_DELTA) over (order by snap_id, BUFFER_GETS_DELTA ), null ) backward from ( select snap_id,sum(BUFFER_GETS_DELTA ) BUFFER_GETS_DELTA from DBA_HIST_SQLSTAT group by snap_id ) x order by 1 ;

Oracle Analytic SQL Select every N-th row select SNAP_ID from ( select snap_id,row_number( ) over (order by snap_id) rn from dba_hist_snapshot ) x where mod(rn,5) = 1 ;

Oracle Analytic SQL Remove Duplicate without use of Distinct select sql_id from ( select sql_id, row_number( ) over (partition by sql_id order by sql_id) rn from DBA_HIST_SQLSTAT ) x where rn = 1 ;

Oracle Analytic SQL Q&A