oracle 中oci 关于null 的处理方法
oci中处理null，必须通过 Indicator 来完成。
使用的oracle 版本 Oracle Database 11g Enterprise Edition Release 11.1.0.6.0
#include <stdlib.h> #include <stdio.h> #include <string.h> #include "include/oci.h" #include "include/ociextp.h" #define ERRGOTO(Recode) do / { / if (Recode!=0) / { / goto ERR; / } / } while (0) void main() { int a = 0 ; OCIDefine* defhp1 = 0; OCIDefine* defhp2 = 0; int blength = 40; char b[40]; sb2 indicator; text *select_sql = (text *)"select a,b from teststmt2"; dvoid *tmp; OCIEnv *envhp; OCIServer *srvhp; OCIError *errhp; OCISvcCtx *svchp; OCISession *usrhp; OCIStmt *stmthp; char serName1[30] ="10.0.4.161:1521/orcl"; char userName1[30] = "cxy"; char pwd1[30] = "cxy"; //!如果没有数据可以使用这个测试用例创建数据表。 //test_BindArrayOfStruct(); memset(b, 0, blength); //!初始化换环境句柄 ERRGOTO(OCIEnvCreate(&(envhp), OCI_DEFAULT, NULL, NULL, NULL, NULL, 0, NULL)); //!初始化错误句柄 ERRGOTO(OCIHandleAlloc((dvoid *)envhp,(dvoid **)&errhp,OCI_HTYPE_ERROR,64,(dvoid **) &tmp)); //!分配服务上下文句柄和服务句柄 ERRGOTO(OCIHandleAlloc((dvoid *)envhp,(dvoid **)&srvhp,OCI_HTYPE_SERVER, 64,(dvoid **) &tmp)); ERRGOTO(OCIHandleAlloc((dvoid *)envhp,(dvoid **)&svchp,OCI_HTYPE_SVCCTX, 64,(dvoid **) &tmp)); //!初始化服务器句柄 ERRGOTO(OCIServerAttach( srvhp, errhp, (text *)serName1, (sb4) strlen(serName1), (ub4) OCI_DEFAULT)); //!/将服务器句柄连接到服务上下文句柄 ERRGOTO(OCIAttrSet ((dvoid *)svchp, OCI_HTYPE_SVCCTX,(dvoid *)srvhp, (ub4) 0, OCI_ATTR_SERVER, errhp)); //!分配设置会话句柄，并向里填充用户名和密码 ERRGOTO(OCIHandleAlloc ((dvoid *)envhp, (dvoid **)&usrhp,OCI_HTYPE_SESSION, 0, (dvoid **) 0)); ERRGOTO(OCIAttrSet ((dvoid *)usrhp, OCI_HTYPE_SESSION,(dvoid *)userName1, (ub4)strlen(userName1),OCI_ATTR_USERNAME, errhp)); ERRGOTO(OCIAttrSet ((dvoid *)usrhp, OCI_HTYPE_SESSION,(dvoid *)pwd1, (ub4)strlen(pwd1),OCI_ATTR_PASSWORD, errhp)); //!建立会话 ERRGOTO(OCISessionBegin (svchp, errhp, usrhp,OCI_CRED_RDBMS, OCI_DEFAULT)); //!将会话句柄连接到服务上下文句柄 ERRGOTO( OCIAttrSet ( (dvoid *)svchp, OCI_HTYPE_SVCCTX,(dvoid *)usrhp, (ub4) 0, OCI_ATTR_SESSION, errhp)); //!分配语句句柄 ERRGOTO(OCIHandleAlloc((dvoid *)envhp, (dvoid **)&stmthp, OCI_HTYPE_STMT, 0, 0)); //!开始查询并获得结果 text *delete_table = (text *)"delete from teststmt2"; ERRGOTO(OCIStmtPrepare(stmthp,errhp,(text *)delete_table,strlen((char *)delete_table),OCI_NTV_SYNTAX,OCI_DEFAULT)); ERRGOTO(OCIStmtExecute(svchp,stmthp,errhp,1,0,0,0,OCI_DEFAULT)); int aa = 8; char bb[] = "bbbbbb"; indicator = -1; text *insert_sql = (text *)"INSERT INTO teststmt2(a,b) values(:1,:2)"; OCIBind* bindhp = 0; //!准备数据，绑定参数 ERRGOTO(OCIStmtPrepare(stmthp,errhp,(text *)insert_sql,strlen((char *)insert_sql),OCI_NTV_SYNTAX,OCI_DEFAULT)); ERRGOTO(OCIBindByPos(stmthp,&bindhp,errhp,1, (dvoid *)&aa,4, SQLT_INT, (void*)&indicator, NULL, NULL,0,0,0)); //OCIBindArrayOfStruct(bindhp,errhp,sizeof(int),0,0,0); ERRGOTO(OCIBindByPos(stmthp,&bindhp,errhp,2,(dvoid *)&bb, 6, SQLT_CHR,NULL,NULL,NULL,0,0,0)); //OCIBindArrayOfStruct(bindhp,errhp,2,0,0,0); //！执行语句 ERRGOTO(OCIStmtExecute(svchp,stmthp,errhp,1,0,0,0,0)); indicator = -1; //!开始查询并获得结果 ERRGOTO(OCIStmtPrepare(stmthp,errhp,(text *)select_sql,strlen((char *)select_sql),OCI_NTV_SYNTAX,OCI_DEFAULT)); //!绑定以一个列 ERRGOTO(OCIDefineByPos(stmthp,&defhp1,errhp,1,&a,sizeof(a),SQLT_INT, (void*)&indicator,0,0,OCI_DEFAULT)); //ERRGOTO(OCIDefineArrayOfStruct(defhp1,errhp,sizeof(int),0,4,0)); //!绑定以二个列 indicator = -2; ERRGOTO(OCIDefineByPos(stmthp,&defhp2,errhp,2,&b, 20, SQLT_CHR, (void*)&indicator, 0, 0, OCI_DEFAULT)); //ERRGOTO(OCIDefineArrayOfStruct(defhp2,errhp,2,0,2,0)); //!执行语句 ERRGOTO(OCIStmtExecute(svchp,stmthp,errhp,1,0,0,0,OCI_DEFAULT)); //ERRGOTO(OCIStmtFetch(stmthp,errhp,1,OCI_FETCH_NEXT,0)); printf("%d, %s, %d", a, b, indicator); ERRGOTO(OCITransCommit(svchp,errhp,0)); //!释放各个资源 //ERRGOTO(OCIHandleFree(srvhp,OCI_HTYPE_SERVER)); //ERRGOTO(OCIHandleFree(errhp,OCI_HTYPE_ERROR)); //ERRGOTO(OCIHandleFree(envhp,OCI_HTYPE_ENV)); return ; ERR: sb4 errcod=0; OraText msgerr[200]=""; OraText msgstat[200]=""; OCIErrorGet(errhp,1,msgstat,&errcod,msgerr,200,OCI_HTYPE_ERROR); printf((char *)msgerr); return; }
官方文档中的描述
Input
For input host variables, the OCI application can assign the following values to an indicator variable:
Table 2-7 Input Indicator Values
| Input Indicator Value | Action Taken by Oracle |
|---|---|
| -1 |
Oracle assigns a |
| >=0 |
Oracle assigns the value of the input variable to the column. |
Output
On output, Oracle can assign the following values to an indicator variable:
Table 2-8 Output Indicator Values
| Output Indicator Value | Meaning |
|---|---|
| -2 |
The length of the item is greater than the length of the output variable; the item has been truncated. Additionally, the original length is longer than the maximum data length that can be returned in the sb2 indicator variable. |
| -1 |
The selected value is null, and the value of the output variable is unchanged. |
|
0 |
Oracle assigned an intact value to the host variable. |
| >0 |
The length of the item is greater than the length of the output variable; the item has been truncated. The positive value returned in the indicator variable is the actual length before truncation. |
Indicator Variables for Named Data Types and REFs
Indicator variables for most new (after release 8.0) datatypes function as described above. The only exception is SQLT_NTY (a named datatype). Data of type SQLT_REF uses a standard scalar indicator, just like other variable types. For data of type SQLT_NTY, the indicator variable must be a pointer to an indicator structure.
When database types are translated into C struct representations using the Object Type Translator (OTT), a null indicator structure is generated for each object type. This structure includes an atomic null indicator, plus indicators for each object attribute.
sb2 indicator ;
对于in
indicator = -1;
OCIBindByPos(stmthp,&bindhp,errhp,1, (dvoid *)&aa,4, SQLT_INT, (void*)&indicator, NULL, NULL,0,0,0))
当indicator = -1;无论绑定的是任何值，插入数据库的全为null
对于out
初始
indicator = 0；
OCIDefineByPos(stmthp,&defhp1,errhp,1,&a,sizeof(a),SQLT_INT, (void*)&indicator,0,0,OCI_DEFAULT);
执行完成，当indicator = -1;如数据库中的值为null，则绑定的值不修改，并且不报错，否则替换成数据库中的值，
如果没传入indicator参数，而只是指定一个空指针的话，报错，说提取的列为null,
-2 和 >0时，测试发现差不多，都是当绑定值小于数据库的值时，把indicator 置为数据库中的实际长度，用处不大
综上所述主要就是indicator = -1，可以在数据库中插入null值，或判断数据库中的是否为null
参数indp是指示符缓冲区，也是一个数组，每个元素是一个sb2类型的值。一般作输入用，如果此项动态参数会被输出，则也作输出用。在输入时，元素值为-1时表示NULL值输入，大于或等于0时是普通得值输入。在输出时，和函数OCIDefineByPos()里的指示符缓冲区作用相同，其值将会在提取数据后填入。其值标志着取到的数值的特殊信息。-2表示值的长度过大，且超过sb4类型的最大值，取出的值被截断，是部分值。-1表示值为NULL，因为C/C++没有NULL这个类型，因此这是判断取出的字段值是否是NULL的唯一方法。0表示数据被完整取出。大于0的值，表示取出的值的字节大小超过定义的每个值的字节大小，取出的值被截断，返回的值是被截断前的字节的大小。