在C語言中調(diào)用Oracle函數(shù)是一種常見的操作。Oracle函數(shù)是自定義的計(jì)算程序，它在Oracle數(shù)據(jù)庫中被存儲，并可以通過SQL語句來調(diào)用。在C語言中，我們可以通過Oracle提供的OCI接口來調(diào)用Oracle函數(shù)，從而實(shí)現(xiàn)對數(shù)據(jù)庫的操作。

在C語言中調(diào)用Oracle函數(shù)需要先連接數(shù)據(jù)庫，然后通過OCI接口進(jìn)行數(shù)據(jù)庫操作。下面是一個簡單的例子：

#include <stdio.h>
#include <oci.h>
int main()
{
// 連接到數(shù)據(jù)庫
OCIEnv *envhp;
OCIEnvCreate(&envhp, OCI_THREADED, (dvoid *)0,
(dvoid * (*)(dvoid *, size_t)) 0,
(dvoid * (*)(dvoid *, dvoid *, size_t))0,
(void (*)(dvoid *, dvoid *)) 0,
(size_t) 0, (dvoid **)0 );
// 初始化OCI環(huán)境
OCIError *errhp;
OCIHandleAlloc((dvoid *) envhp, (dvoid **) &errhp,
OCI_HTYPE_ERROR, (size_t) 0, (dvoid **) 0);
// 連接到數(shù)據(jù)庫
OCISvcCtx *svchp;
OCIHandleAlloc((dvoid *) envhp, (dvoid **) &svchp,
OCI_HTYPE_SVCCTX, (size_t) 0, (dvoid **) 0);
OCIString *str;
OCIStringAlloc((dvoid *) envhp, (dvoid **) &str,
(ub4) 0, (ub2) OCI_UTF16ID);
OCIAttrSet((dvoid *) svchp, (ub4) OCI_HTYPE_SVCCTX,
(dvoid *) str, (ub4) 0, (ub4) OCI_ATTR_SERVICE_NAME,
(OCIError *) errhp);
// 認(rèn)證用戶
OCISession *authp;
OCIHandleAlloc((dvoid *) envhp, (dvoid **) &authp,
OCI_HTYPE_SESSION, (size_t) 0, (dvoid **) 0);
OCIString *uidstr, *pwdstr;
OCIStringAlloc((dvoid *) envhp, (dvoid **) &uidstr,
(ub4) strlen("用戶名"), (ub2) OCI_UTF16ID);
OCIStringAlloc((dvoid *) envhp, (dvoid **) &pwdstr,
(ub4) strlen("密碼"), (ub2) OCI_UTF16ID);
OCISessionBegin(svchp, errhp, authp, OCI_CRED_RDBMS, OCI_DEFAULT);
OCIAttrSet((dvoid *) authp, (ub4) OCI_HTYPE_SESSION,
(dvoid *) uidstr, (ub4) strlen("用戶名"),
(ub4) OCI_ATTR_USERNAME, (OCIError *) errhp);
OCIAttrSet((dvoid *) authp, (ub4) OCI_HTYPE_SESSION,
(dvoid *) pwdstr, (ub4) strlen("密碼"),
(ub4) OCI_ATTR_PASSWORD, (OCIError *) errhp);
OCISessionEnd(svchp, errhp, authp, OCI_DEFAULT);
// 調(diào)用Oracle函數(shù)
OCIDefine *defhp;
OCIStmt *stmthp;
OCIParam *parmp;
OCIBind *bndhp;
OCIDescriptor *descrp;
char *output;
OCIHandleAlloc((dvoid *) envhp, (dvoid **) &stmthp,
OCI_HTYPE_STMT, (size_t) 0, (dvoid **) 0);
OCIStmtPrepare(stmthp, errhp,
"begin :result := my_function(:input); end;", 
(ub4) strlen("begin :result := my_function(:input); end;"), 
(ub4) OCI_NTV_SYNTAX, (ub4) OCI_DEFAULT);
OCIStmtGetPieceInfo(stmthp, errhp, &descrp,
(ub4 *) 0, (ub1 *) 0, (ub1 *) 0,
(ub4) OCI_HTYPE_DESCRIPTOR);
OCIDescriptorAlloc((dvoid *) envhp, &descrp, OCI_DTYPE_PARAM,
(size_t)0, (dvoid **)0);
OCIAttrSet((dvoid *) descrt, (ub4) OCI_DTYPE_PARAM,
(dvoid *) str,
(ub4) strlen("function_name"), OCI_ATTR_NAME,
errhp);
OCIParamGet(stmthp, OCI_HTYPE_STMT, errhp, (dvoid **)&parmp, 1);
OCIAttrSet((dvoid *)parmp, OCI_DTYPE_PARAM,
(dvoid *)&my_input, sizeof(my_input),
OCI_ATTR_VALUE, errhp);
OCIAttrSet((dvoid *)parmp, OCI_DTYPE_PARAM,
(dvoid *)&my_output_len, sizeof(my_output_len),
OCI_ATTR_MAXDATA_SIZE, errhp);
OCIAttrGet((dvoid *)parmp, OCI_DTYPE_PARAM,
(dvoid **)&output, (ub4 *) &my_output_len,
OCI_ATTR_DATA_SIZE, errhp);
OCIStmtExecute(svchp, stmthp, errhp, 1, (ub4) 0,
(OCISnapshot *)0, (OCISnapshot *)0,
OCI_DEFAULT);
printf("%s", output);
return 0;
}

上面代碼中的my_function和my_input是Oracle數(shù)據(jù)庫中的函數(shù)和函數(shù)參數(shù)。我們通過OCI接口將這些參數(shù)傳遞給數(shù)據(jù)庫，并將返回值保存在output中，最終在控制臺上輸出。

總之，在C語言中調(diào)用Oracle函數(shù)是一件非常有用的操作，需要對OCI接口有深入的了解才能實(shí)現(xiàn)。如果需要進(jìn)行數(shù)據(jù)庫操作，這種方法是非常方便、快捷的選擇。