也只能是非查询语句， 允许非查询动态 SQL 语句内包含输入宿主变量占位符, 而且只能带固定数量的宿主变量。使用内嵌PREPARE命令准备SQL语言：
1 PREPARE语法 EXEC SQL PREPARE statement_name FROM {:host_string | string_literal}; PREPARE是一个预编译器标识符,而不是宿主变量2 USING子句 EXEC SQL EXECUTE statement_name [USING :host_variable1[:indicator1] [, :host_variable2[:indicator2] … ]demo2 #include <stdio.h> #include <string.h> #include <stdlib.h> #include "sqlca.h" #include "oraca.h" typedef char mydname[20]; typedef char myloc[20]; //库函数 extern sqlgls(char * , size_t *, size_t * ); extern sqlglmt(void *,char *,size_t *,size_t *); //定义宿主变量 EXEC SQL BEGIN DECLARE SECTION; EXEC SQL TYPE mydname is string(20); EXEC SQL TYPE myloc is string(20); char *serverid = "c##scott/root"; int deptno; dnameType dname; locType loc; char mySql[1024]; char *pSql; EXEC SQL END DECLARE SECTION; int connet(); void doerr(); int main() { int ret = 0; char inputchar; memset(mySql, 0, sizeof(mySql)); pSql = NULL; EXEC SQL WHENEVER sqlerror do doerr(); connet(); pSql = mySql; // 处理sql语言 for(;;) { printf("\n请输入要更新部门编号 "); scanf("%d", &deptno); printf("\n请输入要新loc值 "); scanf("%s", loc); //准备动态sql (2个占位符) EXEC SQL PREPARE my_pre_sql FROM 'update dept set loc = :aa where deptno = :bb'; //执行动态sql EXEC SQL EXECUTE my_pre_sql USING :loc, :deptno; // EXEC SQL COMMIT; printf("\n any key to continue? "); getchar(); printf("\n exit:n, other continue? "); scanf("%c", &inputchar); fflush(stdin); if (inputchar=='n' || inputchar=='N') { break; } } EXEC SQL COMMIT WORK RELEASE; return ret ; } int connet() { int ret = 0; //连接数据库 EXEC SQL connect :serverid; if (sqlca.sqlcode != 0) { ret = sqlca.sqlcode; return ret; } else { printf("connect ok...\n"); } return ret; } void doerr() { char szerrbuf[120]; size_t outputlen, inputlen = 120; unsigned int ret = 0; //出错时,可以把错误SQL语言给打印出来 EXEC SQL WHENEVER SQLERROR CONTINUE; ret = sqlgls(szerrbuf, &inputlen, &outputlen); printf("SQL:%.*s\n", inputlen, szerrbuf); printf("提示:%.*s\n", sqlca.sqlerrm.sqlerrml, sqlca.sqlerrm.sqlerrmc); EXEC SQL ROLLBACK WORK RELEASE; exit(1); }