oracle – 除非我存储值,否则Sequence不会递增

在常规SQL中,每次调用时,我的序列都会递增.NEXTVAL：

SELECT PDF_DATOS_TITULO_ID_SEQ.CURRVAL FROM DUAL; -- 54
SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL; -- 55
SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL; -- 56
SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL; -- 57
SELECT PDF_DATOS_TITULO_ID_SEQ.CURRVAL FROM DUAL; -- 57 (54+3,correct)

但是,在PL / SQL块内的动态SQL中,它不会增加：

SELECT PDF_DATOS_TITULO_ID_SEQ.CURRVAL FROM DUAL; -- 57
BEGIN
    EXECUTE IMMEDIATE 'SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL';
    EXECUTE IMMEDIATE 'SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL';
    EXECUTE IMMEDIATE 'SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL';
END;
/
SELECT PDF_DATOS_TITULO_ID_SEQ.CURRVAL FROM DUAL; -- 57

…除非我将值存储到变量中：

SELECT PDF_DATOS_TITULO_ID_SEQ.CURRVAL FROM DUAL; -- 57 (!)
DECLARE
    FOO INTEGER;
BEGIN
    EXECUTE IMMEDIATE 'SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL' INTO FOO;
    EXECUTE IMMEDIATE 'SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL' INTO FOO;
    EXECUTE IMMEDIATE 'SELECT PDF_DATOS_TITULO_ID_SEQ.NEXTVAL FROM DUAL' INTO FOO;
END;
/
SELECT PDF_DATOS_TITULO_ID_SEQ.CURRVAL FROM DUAL; -- 60 (57+3,correct)

解释是什么？它是EXECUTE IMMEDIATE的记录行为吗？

在您提出要求之前,SQL需要是动态的,因为序列名称是可变的.

解决方法

例如.：

SQL> create sequence testseq;

Sequence created.

SQL> alter session set events '10046 trace name context forever';

Session altered.

SQL> exec execute immediate 'select testseq.nextval from dual';

PL/SQL procedure successfully completed.

SQL> alter session set events '10046 trace name context off';

Session altered.

SQL> exit

我们在跟踪中看到Oracle没有对FETCH阶段感到困扰：

=====================
PARSING IN CURSOR #140341213531640 len=32 dep=1 uid=83 oct=3 lid=83 tim=1363260261727946 hv=956010684 ad='7ac66b58' sqlid='56jwk2hwgr45w'
select testseq.nextval from dual
END OF STMT
PARSE #140341213531640:c=4001,e=50473,p=0,cr=2,cu=0,mis=1,r=0,dep=1,og=1,plh=112670795,tim=1363260261727944
EXEC #140341213531640:c=0,e=219,cr=0,mis=0,tim=1363260261728249
STAT #140341213531640 id=1 cnt=0 pid=0 pos=1 obj=79530 op='SEQUENCE  TESTSEQ (cr=0 pr=0 pw=0 time=181 us)'
STAT #140341213531640 id=2 cnt=0 pid=1 pos=1 obj=0 op='FAST DUAL  (cr=0 pr=0 pw=0 time=1 us cost=2 size=0 card=1)'
CLOSE #140341213531640:c=4001,e=24391,type=3,tim=1363260261752736
EXEC #140341212444728:c=8002,e=75407,r=1,dep=0,plh=0,tim=1363260261752783

*** 2013-03-14 11:24:29.866
CLOSE #140341212444728:c=0,e=37,type=0,tim=1363260269866098
=====================

VS：

SQL> alter session set events '10046 trace name context forever';

Session altered.

SQL> var a number
SQL> exec execute immediate 'select testseq.nextval from dual' into :a;

PL/SQL procedure successfully completed.

SQL> alter session set events '10046 trace name context off';

Session altered.

现在：

PARSING IN CURSOR #139830768042232 len=32 dep=1 uid=83 oct=3 lid=83 tim=1363260428931803 hv=956010684 ad='7ac66b58' sqlid='56jwk2hwgr45w'
select testseq.nextval from dual
END OF STMT
PARSE #139830768042232:c=0,e=38,tim=1363260428931802
EXEC #139830768042232:c=0,e=86,tim=1363260428931917
FETCH #139830768042232:c=0,e=22,tim=1363260428931980
STAT #139830768042232 id=1 cnt=1 pid=0 pos=1 obj=79530 op='SEQUENCE  TESTSEQ (cr=0 pr=0 pw=0 time=39 us)'
STAT #139830768042232 id=2 cnt=1 pid=1 pos=1 obj=0 op='FAST DUAL  (cr=0 pr=0 pw=0 time=2 us cost=2 size=0 card=1)'
CLOSE #139830768042232:c=0,e=0,tim=1363260428931980
EXEC #139830768045912:c=0,e=294,tim=1363260428931980

*** 2013-03-14 11:27:13.138
CLOSE #139830768045912:c=0,e=45,tim=1363260433138490
=====================

可以看到FETCH.我认为理想情况下,Oracle应该在用户发出没有定义INTO / BULK INTO的选择的情况下抛出错误.

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