[英]how to optimize pl sql if statement with multiple OR conditions
我是pl sql的新手,請告訴我如何優化以下if語句?
IF (inSeries=‘90’) OR (inSeries=‘91’) OR (inSeries=‘92’) OR (inSeries=‘93’) OR (inSeries=‘94’) THEN
像在SQL中,我們可以使用
WHERE inSeries IN (‘90’,’91’,’92’,’93’,’94’)
在PLSQL中,“ IN”條件也可用作IF條件
declare
inSeries varchar2(2) := '90';
begin
if inseries in ('90','91','92','93','94')
then
dbms_output.put_line(inseries ||':this is within series');
else
dbms_output.put_line(inseries ||':this is out of series');
end if;
end;
-- output
90:this is within series
80:this is out of series
但是還有另一種方式取決於業務邏輯,正如我從您的問題中看到的那樣,它以系列遞增,您可以直接使用大於和小於組合...
優化程序很可能會重寫查詢,因此您的IN
仍將變為OR
。 比較查詢中的第3行和最后一行:
SQL> select job
2 from emp
3 where deptno in (10, 20, 30, 40);
JOB
---------
CLERK
SALESMAN
<snip>
14 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 14 | 154 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| EMP | 14 | 154 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("DEPTNO"=10 OR "DEPTNO"=20 OR "DEPTNO"=30 OR "DEPTNO"=40)
SQL>
您可以將SQL查詢本身與“ EXISTS”關鍵字一起使用。
IF EXISTS (SELECT * FROM <table_name> WHERE inSeries IN (‘90’,’91’,’92’,’93’,’94’))
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