PLSQL_低效SQL的识别和查询汇总（案例）

SELECT   HASH_VALUE,
SQL_TEXT,
SORTS,
EXECUTIONS
FROM   V$SQLAREA
ORDER BY   SORTS DESC;

SELECT   *
FROM   (  SELECT   sql_text,
disk_reads "total disk",
executions "total exec",
disk_reads / executions "disk/exec"
FROM   v$sql
WHERE   executions > 0 AND is_obsolete = 'N'
ORDER BY   4 DESC)
WHERE   ROWNUM < 11;

SELECT   SUBSTR (TO_CHAR (s.pct, '99.00'), 2) || '%' load,
s.executions executes,
p.sql_text
FROM   (SELECT   address,
disk_reads,
executions,
pct,
RANK () OVER (ORDER BY disk_reads DESC) ranking
FROM   (SELECT   address,
disk_reads,
executions,
100 * ratio_to_report (disk_reads) OVER () pct
FROM   sys.v_$sql
WHERE   command_type != 47)
WHERE   disk_reads > 50 * executions) s, sys.v_$sqltext p
WHERE   s.ranking <= 5 AND p.address = s.address
ORDER BY   1, s.address, p.piece;

SELECT   executions,
disk_reads,
buffer_gets,
ROUND ( (buffer_gets - disk_reads) / buffer_gets, 2) Hit_radio,
ROUND (disk_reads / executions, 2) reads_per_run,
sql_text
FROM   v$sqlarea
WHERE       executions > 0
AND buffer_gets > 0
AND (buffer_gets - disk_reads) / buffer_gets < 0.8
ORDER BY   4 DESC;