[20231124]奇怪的高逻辑读4.txt

[20231124]奇怪的高逻辑读4.txt

--//很长一段在生产系统看到一条逻辑读很高的sql语句,检查发现谓词使用了DBMS_LOB.SUBSTR函数.
--//开发真奇葩,我无论如何也想不出开发为什么这些写代码,当时脑子短路了,使用trunc还好理解一点.
--//我开始以为主要原因是lob类型导致fetch记录是1行1行提取,逻辑读提高,但是实测的效果要高出许多倍.当时没有继续探究,今天继续
--//探究看看,顺便尝试是否建立函数索引.
--//以前的测试链接:http://blog.itpub.net/267265/viewspace-2936071/=>[20230216]奇怪的高逻辑读3.txt.

1.环境:
SCOTT@book> @ ver1
PORT_STRING         VERSION    BANNER
------------------- ---------- ----------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

2.建立测试例子:
SCOTT@book> create table t as select * from all_objects where rownum <=100;
Table created.

--//分析略.
--//@ gts t '' ''

SCOTT@book> @ desc_proc sys  dbms_lob substr
INPUT OWNER PACKAGE_NAME OBJECT_NAME
sample : @desc_proc sys dbms_stats gather_%_stats

OWNER PACKAGE_NAME OBJECT_NAME SEQUENCE ARGUMENT_NAME DATA_TYPE IN_OUT    DEFAULTED
----- ------------ ----------- -------- ------------- --------- --------- ----------
SYS   DBMS_LOB     SUBSTR             1               RAW       OUT       N
                                      2 LOB_LOC       BLOB      IN        N
                                      3 AMOUNT        NUMBER    IN        Y
                                      4 OFFSET        NUMBER    IN        Y
                                      1               VARCHAR2  OUT       N
                                      2 LOB_LOC       CLOB      IN        N
                                      3 AMOUNT        NUMBER    IN        Y
                                      4 OFFSET        NUMBER    IN        Y
                                      1               RAW       OUT       N
                                      2 FILE_LOC      BFILE     IN        N
                                      3 AMOUNT        NUMBER    IN        Y
                                      4 OFFSET        NUMBER    IN        Y
12 rows selected.
--//dbms_lob.substr函数参数与substr不一样,第2个参数AMOUNT表示取字符串的数量,第3个参数OFFSET表示字符串的偏移量.
--//注意最后一列DEFAULTED表明可以不输入第2,3参数(Y),不知道缺省怎么值.可以根据下面的执行推断offset缺省值=1.
--//注意返回数据类型支持raw,varchar2.

3.测试:
SCOTT@book> @ sl all
alter session set statistics_level = all;
Session altered.

SCOTT@book> select * from t where dbms_lob.substr(object_name)='DEPT';
no rows selected

SCOTT@book> @ dpc '' '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  7fybpwpmd0svt, child number 0
-------------------------------------
select * from t where dbms_lob.substr(object_name)='DEPT'
Plan hash value: 1601196873
--------------------------------------------------------------------------------------------------------------------
| Id  | Operation         | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |      1 |        |       |     3 (100)|          |      0 |00:00:00.02 |    1298 |
|*  1 |  TABLE ACCESS FULL| T    |      1 |      1 |    75 |     3   (0)| 00:00:01 |      0 |00:00:00.02 |    1298 |
--------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$1 / T@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter("DBMS_LOB"."SUBSTR"(INTERNAL_FUNCTION("OBJECT_NAME"))='DEPT')
--//测试多次,最后稳定在1298逻辑读.

SCOTT@book> select * from t where dbms_lob.substr(object_name,30.0,1.0)='ICOL$';
SCOTT@book> @ pr
==============================
OWNER                         : SYS
OBJECT_NAME                   : ICOL$
SUBOBJECT_NAME                :
OBJECT_ID                     : 20
DATA_OBJECT_ID                : 2
OBJECT_TYPE                   : TABLE
CREATED                       : 2013-08-24 11:37:35
LAST_DDL_TIME                 : 2013-08-24 11:47:37
TIMESTAMP                     : 2013-08-24:11:37:35
STATUS                        : VALID
TEMPORARY                     : N
GENERATED                     : N
SECONDARY                     : N
NAMESPACE                     : 1
EDITION_NAME                  :
PL/SQL procedure successfully completed.

SCOTT@book> @ dpc '' '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  baj2g6ratkpgq, child number 0
-------------------------------------
select * from t where dbms_lob.substr(object_name,30.0,1.0)='ICOL$'
Plan hash value: 1601196873
--------------------------------------------------------------------------------------------------------------------
| Id  | Operation         | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |      1 |        |       |     3 (100)|          |      1 |00:00:00.02 |    1299 |
|*  1 |  TABLE ACCESS FULL| T    |      1 |      1 |    75 |     3   (0)| 00:00:01 |      1 |00:00:00.02 |    1299 |
--------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$1 / T@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter("DBMS_LOB"."SUBSTR"(INTERNAL_FUNCTION("OBJECT_NAME"),30,1)='ICOL$')
--//如果查询有返回值,逻辑读增加1个.

SCOTT@book> with a as (select /*+ materialize */ dbms_lob.substr(object_name) xx,t.* from t ) select * from a where a.xx='DEPT';
no rows selected

SCOTT@book> @ dpc '' '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  5x7x0rn7294bk, child number 0
-------------------------------------
with a as (select /*+ materialize */ dbms_lob.substr(object_name)
xx,t.* from t ) select * from a where a.xx='DEPT'
Plan hash value: 2328698527
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                  | Name                        | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads  | Writes |  OMem |  1Mem | Used-Mem |
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT           |                             |      1 |        |       |     5 (100)|          |      0 |00:00:00.06 |    1315 |      2 |      2 |       |       |          |
|   1 |  TEMP TABLE TRANSFORMATION |                             |      1 |        |       |            |          |      0 |00:00:00.06 |    1315 |      2 |      2 |       |       |          |
|   2 |   LOAD AS SELECT           |                             |      1 |        |       |            |          |      0 |00:00:00.06 |    1303 |      0 |      2 |   270K|   270K|  270K (0)|
|   3 |    TABLE ACCESS FULL       | T                           |      1 |    100 |  7500 |     3   (0)| 00:00:01 |    100 |00:00:00.01 |       3 |      0 |      0 |       |       |          |
|*  4 |   VIEW                     |                             |      1 |    100 |   210K|     2   (0)| 00:00:01 |      0 |00:00:00.01 |       6 |      2 |      0 |       |       |          |
|   5 |    TABLE ACCESS FULL       | SYS_TEMP_0FD9D6603_17823151 |      1 |    100 |  7500 |     2   (0)| 00:00:01 |    100 |00:00:00.01 |       6 |      2 |      0 |       |       |          |
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$2
   2 - SEL$1
   3 - SEL$1        / T@SEL$1
   4 - SEL$D67CB2D2 / A@SEL$2
   5 - SEL$D67CB2D2 / T1@SEL$D67CB2D2
Predicate Information (identified by operation id):
---------------------------------------------------
   4 - filter("A"."XX"='DEPT')

4.继续:
--//但是如果执行如下:
select t.*,dbms_lob.substr(object_name) from t;
select t.* from t;

--//两者的逻辑读都是4.
SCOTT@book> @ dpc '' '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  9s1tjxvnfwkxj, child number 0
-------------------------------------
select t.* from t
Plan hash value: 1601196873
--------------------------------------------------------------------------------------------------------------------
| Id  | Operation         | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |      1 |        |       |     3 (100)|          |    100 |00:00:00.01 |       4 |
|   1 |  TABLE ACCESS FULL| T    |      1 |    100 |  7500 |     3   (0)| 00:00:01 |    100 |00:00:00.01 |       4 |
--------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$1 / T@SEL$1

SCOTT@book> @ dpc '' '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  gxspjy1yabrmp, child number 0
-------------------------------------
select t.*,dbms_lob.substr(object_name) from t
Plan hash value: 1601196873
--------------------------------------------------------------------------------------------------------------------
| Id  | Operation         | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |      1 |        |       |     3 (100)|          |    100 |00:00:00.01 |       4 |
|   1 |  TABLE ACCESS FULL| T    |      1 |    100 |  7500 |     3   (0)| 00:00:01 |    100 |00:00:00.01 |       4 |
--------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$1 / T@SEL$1
--//这是我前面测试不能理解的地方,至少应该有一点点区别.难道这样的函数访问,在oracle的执行计划里面逻辑读不计数吗?
--//如果你看前面使用materialize也可以看出逻辑读不应该是这个数量.

5.尝试是否可以建立索引.
--//注意前面的过滤存在一个INTERNAL_FUNCTION.
   1 - filter("DBMS_LOB"."SUBSTR"(INTERNAL_FUNCTION("OBJECT_NAME"))='DEPT')

SCOTT@book> create index if_t_object_name on t(DBMS_LOB.SUBSTR(OBJECT_NAME)) ;
Index created.

--//ok,索引可以建立!!

SCOTT@book> select * from t where dbms_lob.substr(object_name)='ICOL$';
SCOTT@book> @ dpc '' '' ''
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  fxs2sk8mvtp5s, child number 0
-------------------------------------
select * from t where dbms_lob.substr(object_name)='ICOL$'
Plan hash value: 1757252843
------------------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name             | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
------------------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |                  |      1 |        |       |     2 (100)|          |      1 |00:00:00.01 |       3 |
|   1 |  TABLE ACCESS BY INDEX ROWID| T                |      1 |      1 |    75 |     2   (0)| 00:00:01 |      1 |00:00:00.01 |       3 |
|*  2 |   INDEX RANGE SCAN          | IF_T_OBJECT_NAME |      1 |      1 |       |     1   (0)| 00:00:01 |      1 |00:00:00.01 |       2 |
------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
   1 - SEL$1 / T@SEL$1
   2 - SEL$1 / T@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
   2 - access("T"."SYS_NC00016$"='ICOL$')
--//很好,可以很好地使用我建立的函数索引.

6.继续分析看看为什么前面的逻辑读是4.

SCOTT@book> drop index IF_T_OBJECT_NAME;
Index dropped.

--//开启跟踪:
SCOTT@book>  alter system set "_trace_pin_time"=1 scope=spfile;
System altered.
--//重启数据库略.

SCOTT@book> @ t
TRACEFILE
-------------------------------------------------------------
/u01/app/oracle/diag/rdbms/book/book/trace/book_ora_10291.trc

--//执行如下多次.
select t.*,dbms_lob.substr(object_name) from t;
select t.*,dbms_lob.substr(object_name) from t;
select t.*,dbms_lob.substr(object_name) from t;

$ >| /u01/app/oracle/diag/rdbms/book/book/trace/book_ora_10291.trc

select t.*,dbms_lob.substr(object_name) from t;

$ cp  /u01/app/oracle/diag/rdbms/book/book/trace/book_ora_10291.trc 20231128.txt

$ head 20231128.txt
pin ktewh26: kteinpscan dba 0x100041a:4 time 1562795234
pin kdswh11: kdst_fetch dba 0x100041b:1 time 1562795764
pin ktswh102: ktsbvini dba 0x40ce80:4 time 1562795899
pin release        26 ktswh102: ktsbvini dba 0x40ce80:4
pin ktswh100: ktsbgsp dba 0x40ce81:12 time 1562795946
pin release        15 ktswh100: ktsbgsp dba 0x40ce81:12
pin ktswh133: ktsbvopn dba 0x40ce80:4 time 1562795976
pin release        14 ktswh133: ktsbvopn dba 0x40ce80:4
pin ktswh108: ktsbbsrch dba 0x40ce82:11 time 1562796006
pin release        28 ktswh108: ktsbbsrch dba 0x40ce82:11

$ awk '{print $2}' 20231128.txt | sort | uniq -c | sort -rn
   1200 release
    300 ktswh133:
    200 ktswh102:
    100 ktswh134:
    100 ktswh123:
    100 ktswh111:
    100 ktswh110:
    100 ktswh108:
    100 ktswh100:
    100 kdlwh01:
    100 kdlwh00:
      3 kdswh11:
      1 ktewh26:
--//可以发现并不是不访问数据块,仅仅执行计划对于这类情况不计数罢了.

SCOTT@book> select min(rowid),max(rowid) from t;
MIN(ROWID)         MAX(ROWID)
------------------ ------------------
AAAWe0AAEAAAAQbAAA AAAWe0AAEAAAAQcAAL

SCOTT@book> @ rowid AAAWe0AAEAAAAQbAAA
    OBJECT       FILE      BLOCK        ROW ROWID_DBA            DBA                  TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
     92084          4       1051          0  0x100041B           4,1051               alter system dump datafile 4 block 1051

SCOTT@book> @ rowid AAAWe0AAEAAAAQcAAL
    OBJECT       FILE      BLOCK        ROW ROWID_DBA            DBA                  TEXT
---------- ---------- ---------- ---------- -------------------- -------------------- ----------------------------------------
     92084          4       1052         11  0x100041C           4,1052               alter system dump datafile 4 block 1052

$ egrep "0x100041" 20231128.txt
pin ktewh26: kteinpscan dba 0x100041a:4 time 1562795234
pin kdswh11: kdst_fetch dba 0x100041b:1 time 1562795764
pin kdswh11: kdst_fetch dba 0x100041b:1 time 1562797381
pin kdswh11: kdst_fetch dba 0x100041c:1 time 1562844412
--//扫描表对应块0x100041a,0x100041b,0x100041c, 仅仅4次逻辑读.

$ grep "pin release" 20231128.txt | awk '{print $7}' | sort | uniq -c
    600 0x40ce80:4
    200 0x40ce81:12
    300 0x40ce82:11
     50 0x40ce83:1
     50 0x40ce84:1

--//0x40ce80 = set dba 1,52864 = alter system dump datafile 1 block 52864 = 4247168
--//0x40ce84 = set dba 1,52868 = alter system dump datafile 1 block 52868 = 4247172

SYS@book> @ find_objz 1 52864  '' 1
SYS@book> @ pr
==============================
FILE_ID                       : 1
BLOCK_ID                      : 52480
BLOCKS                        : 1024
SEGMENT_TYPE                  : TABLE
OWNER                         : SYS
SEGMENT_NAME                  : IDL_UB1$
PARTITION_NAME                :
EXTENT_ID                     : 89
BYTES                         : 8388608
TABLESPACE_NAME               : SYSTEM
RELATIVE_FNO                  : 1
SEGTSN                        : 0
SEGRFN                        : 1
SEGBID                        : 1512
PL/SQL procedure successfully completed.
--//这次测试与前面的不同,访问的是SYS.IDL_UB1$.前面的测试如下,访问的是sys.ARGUMENT$.
--//以前的测试链接:http://blog.itpub.net/267265/viewspace-2936071/=>[20230216]奇怪的高逻辑读3.txt.
--//我再次重复前面的测试,不知道当时错误在那里,确实访问的是SYS.IDL_UB1$.
--//我甚至从冷备份恢复测试确实访问的是SYS.IDL_UB1$.

SYS@book>  @ o2 sys.IDL_UB1$
SYS@book> @ pr
==============================
O_OWNER                       : SYS
O_OBJECT_NAME                 : IDL_UB1$
O_OBJECT_TYPE                 : TABLE
SEG_PART_NAME                 :
O_STATUS                      : VALID
OID                           : 225
D_OID                         : 225
CREATED                       : 2013-08-24 11:37:39
LAST_DDL_TIME                 : 2013-08-24 11:37:39
PL/SQL procedure successfully completed.

SCOTT@book> @ cr_rowid 225 1 52864 0
argument list : data_object_id file# block# row#
CREATE_ROWID
------------------
AAAADhAABAAAM6AAAA

SCOTT@book> @ cr_rowid 225 1 52868 800
argument list : data_object_id file# block# row#
CREATE_ROWID
------------------
AAAADhAABAAAM6EAMg

SCOTT@book> SELECT *  FROM sys.idl_ub1$ WHERE ROWID BETWEEN 'AAAADhAABAAAM6AAAA' AND 'AAAADhAABAAAM6EAMg';
      OBJ#       PART    VERSION     PIECE#     LENGTH P
---------- ---------- ---------- ---------- ---------- -
     57638          1          0          0      38743 F

SCOTT@book> SELECT *  FROM sys.idl_ub1$ WHERE DBMS_ROWID.ROWID_BLOCK_NUMBER(rowid) between 52864 and 52868;
      OBJ#       PART    VERSION     PIECE#     LENGTH P
---------- ---------- ---------- ---------- ---------- -
     57638          1          0          0      38743 F

SYS@book> @ desc sys.idl_ub1$
           Name                            Null?    Type
           ------------------------------- -------- ----------------------------
    1      OBJ#                            NOT NULL NUMBER
    2      PART                            NOT NULL NUMBER
    3      VERSION                                  NUMBER
    4      PIECE#                          NOT NULL NUMBER
    5      LENGTH                          NOT NULL NUMBER
    6      PIECE                           NOT NULL LONG RAW
--//确实仅仅有1个对象,PIECE类型为long raw占用许多空间,38743/8000 = 4.8,占5块。

SYS@book> @ oid 57638
SYS@book> @ pr
==============================
O_OWNER                       : SYS
O_OBJECT_NAME                 : /a76131c0_XSLTErrorResources_e
O_OBJECT_TYPE                 : JAVA CLASS
SUBOBJECT_NAME                :
CREATED                       : 2013-08-24 11:45:29
LAST_DDL_TIME                 : 2013-08-24 11:45:29
O_STATUS                      : VALID
DATA_OBJECT_ID                :
OBJECT_ID                     : 57638
PL/SQL procedure successfully completed.
--//也就是调用DBMS_LOB.SUBSTR要访问oid=57638对象多次。

SCOTT@book> create index if_t_object_name on t(DBMS_LOB.SUBSTR(OBJECT_NAME)) ;
Index created.

select * from t where dbms_lob.substr(object_name)='ICOL$';
select * from t where dbms_lob.substr(object_name)='ICOL$';
select * from t where dbms_lob.substr(object_name)='ICOL$';
--//执行多次。

$ >| /u01/app/oracle/diag/rdbms/book/book/trace/book_ora_10698.trc
$ cp /u01/app/oracle/diag/rdbms/book/book/trace/book_ora_10698.trc 20231128a.txt

SCOTT@book> select * from t where dbms_lob.substr(object_name)='ICOL$';
...

$ egrep "dba 0x1000" 20231128a.txt
pin qeilwhrp: qeilbk dba 0x1000423:1 time 4238232606
pin kdswh05: kdsgrp dba 0x100041b:1 time 4238232706
pin kdiwh16: kdifxs dba 0x1000423:1 time 4238233321
--//0x1000423 应该访问的索引数据块.

$ egrep "dba " 20231128a.txt
pin qeilwhrp: qeilbk dba 0x1000423:1 time 4238232606
pin kdswh05: kdsgrp dba 0x100041b:1 time 4238232706
pin kdiwh16: kdifxs dba 0x1000423:1 time 4238233321
--//完全看不到dba 0x40ce8X的访问。

7.收尾:
SCOTT@book> alter system reset "_trace_pin_time";
System altered.

--//重启略。

> @ ashtable d DBMS_LOB.SUBSTR 1=1 &day
@ tpt/dashtop sql_id,module "1=1 and sql_id in (select sql_id from v$sqlarea where lower(sql_fulltext) like lower('%DBMS_LOB.SUBSTR%'))"  sysdate-1 sysdate

    Total
  Seconds     AAS %This    SQL_ID        MODULE                         FIRST_SEEN          LAST_SEEN
--------- ------- -------  ------------- ------------------------------ ------------------- -------------------
     2200      .0   55%    18vdbxnv6kt3f uwsgi@YDHL_100212 (TNS V1-V3)  2023-11-27 15:08:21 2023-11-28 10:47:19
     1810      .0   45%    df54kmrg2yz8t uwsgi@YDHL_100212 (TNS V1-V3)  2023-11-27 11:50:06 2023-11-28 10:57:40

> @ sql_id 18vdbxnv6kt3f
--SQL_ID = 18vdbxnv6kt3f
SELECT "V_YDHL_EMPLOYEES"."ORGAN_CODE"
     , "V_YDHL_EMPLOYEES"."ID"
     , "V_YDHL_EMPLOYEES"."USER_NAME"
     , "V_YDHL_EMPLOYEES"."PASSWORD"
     , "V_YDHL_EMPLOYEES"."USER_CODE"
     , "V_YDHL_EMPLOYEES"."STAFF_NAME"
     , "V_YDHL_EMPLOYEES"."PHONE"
     , "V_YDHL_EMPLOYEES"."USER_TYPE"
     , "V_YDHL_EMPLOYEES"."IS_VALID"
     , "V_YDHL_EMPLOYEES"."IS_ADMIN"
     , "V_YDHL_EMPLOYEES"."SIGNATURE"
     , "V_YDHL_EMPLOYEES"."AUTH"
  FROM "V_YDHL_EMPLOYEES"
 WHERE DBMS_LOB.SUBSTR("V_YDHL_EMPLOYEES"."USER_NAME") = :arg0;

> @ bind_cap 18vdbxnv6kt3f ''
SQL_ID        CHILD_NUMBER WAS NAME   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- ------ -------- ---------- ------------------- --------------- --------------
18vdbxnv6kt3f            0 YES :ARG0         1        128 2023-11-28 00:27:16 VARCHAR2(128)   5621
                         1 YES :ARG0         1         32 2023-11-28 04:59:51 VARCHAR2(32)    4560
                         2 YES :ARG0         1        128 2023-11-28 11:44:36 VARCHAR2(128)   1876

--//感觉开发写的有问题,USER_NAME应该类似名字,而查询输入的确实员工代码.
--//我仅仅想说写成这样的代码人不知道那个学校毕业的,实在想不出为什么这样写sql语句。

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