Question

：d 我正在阅读sqlite（owens，allen）的权威指南，并决定在这本精美的书中试验一些代码并遇到一些编译问题。我希望能够挤出一些这些问题并同时学习一些C和SQLite！哇呀！

编译时我收到以下神秘的编译错误： gcc mo.c -o m -lsqlite3

mo.c: In function ‘main’:
mo.c:22:44: error: ‘nrows’ undeclared (first use in this function)
mo.c:22:44: note: each undeclared identifier is reported only once for each function
it appears in
mo.c:22:52: error: ‘ncols’ undeclared (first use in this function)
mo.c:22:2: warning: passing argument 3 of ‘sqlite3_get_table’ from incompatible pointer 
type [enabled by default]
/usr/local/include/sqlite3.h:2084:16: note: expected ‘char ***’ but argument is of  
type  ‘char * (*)[50]’

我最为困惑的是“警告：从不兼容的指针类型[默认启用]传递'sqlite3_get_table'的参数3”和“注意：预期'char * '但参数类型为' char *（*）[50]'

有问题的程序如下：你能不能实现stackoverflow？＆LT; ================================================ ===================================＆GT;

#include <stdio.h>
#include <sqlite3.h>
#include <stdlib.h>

int main()
{
sqlite3 *db;
char *zErr;
int rc;
char *sql;
char *result[50];
int j=0;
int i=0;
rc = sqlite3_open("foods-backup.db", &db);

if(rc) {
    fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
    sqlite3_close(db);
    exit(1);
}

rc = sqlite3_get_table(db, sql, &result, &nrows, &ncols, &zErr);

for(i; i < nrows; i++) {
  for(j; j < ncols; j++) {
    /* the i+1 term skips over the first record,
    which is the column headers */
    fprintf(stdout, "%s", result[(i+1)*ncols + j]);
  }
}



if(rc != SQLITE_OK) {
    if (zErr != NULL) {
  fprintf(stderr, "SQL error: %s\n", zErr);
        sqlite3_free(zErr);
    }
}



 /* Free memory */
sqlite3_free_table(result);
// close database connection or something and return everything is okay i guess
sqlite3_close(db);
return 0;
} // end main

Answer 1

你得到的错误是因为 1. nrows，ncols变量未声明。它们应该被声明为整数。 2. result变量应声明为char **而不是char *result[50]。

因此注释掉你的结果数组指针声明并复制到两行以下。希望这会有所帮助。

int nrows, ncols;
char **result;

http://www.sqlite.org/c3ref/free_table.html

int sqlite3_get_table(
sqlite3 *db,          /* An open database */
const char *zSql,     /* SQL to be evaluated */
char ***pazResult,    /* Results of the query */
int *pnRow,           /* Number of result rows written here */
int *pnColumn,        /* Number of result columns written here */
char **pzErrmsg       /* Error msg written here */

）;

SQLite3连接到C程序并使用内部循环来迭代结果 - 怎么办？

1 个答案: