MySQL入门之一次函数调用执行多条语句
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2022-04-06 12:57:30
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支持在单个字符串中指定的多语句的执行。要想与给定的连接一起使用该功能,打开连接时,必须将标志参数中的CLIENT_MULTI_STATEMENTS选项指定给mysql_real_connect()。也可以通过调用mysql_set_server_option(MYSQL_OPTION_MULTI_STATEMENTS_ON),为已有的连接设置它。
常用套路:
/* Connect to server with option CLIENT_MULTI_STATEMENTS */ mysql_real_connect(..., CLIENT_MULTI_STATEMENTS); /* Now execute multiple queries */ mysql_query(mysql,"DROP TABLE IF EXISTS test_table;\ CREATE TABLE test_table(id INT);\ INSERT INTO test_table VALUES(10);\ UPDATE test_table SET id=20 WHERE id=10;\ SELECT * FROM test_table;\ DROP TABLE test_table"); do { /* Process all results */ ... printf("total affected rows: %lld", mysql_affected_rows(mysql)); ... if (!(result= mysql_store_result(mysql))) { printf(stderr, "Got fatal error processing query\n"); exit(1); } process_result_set(result); /* client function */ mysql_free_result(result); } while (!mysql_next_result(mysql));
具体看代码:
#include <stdio.h> #include <stdlib.h> #include <string.h> #include <dlfcn.h> #include <mysql/mysql.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <errno.h> #include <termios.h> #include <mysql/mysql.h> void process_result_set(MYSQL *mysql, MYSQL_RES *result) { int i =0; unsigned int fieldnum; //从结果集,获取表头信息 MYSQL_FIELD *fields = mysql_fetch_fields(result); fieldnum = mysql_field_count(mysql); for (i=0; i<fieldnum; i++) { printf("%s\t", fields[i].name); } printf("\n"); //从结果集, 按照行获取信息信息 MYSQL_ROW row = NULL; //从结果集中一行一行的获取数据 while ( row = mysql_fetch_row(result)) { fieldnum = mysql_field_count(mysql); //优化,我的行有多少列。。。。查找这样的api函数 for (i=0; i<fieldnum; i++) //经过测试 发现 不是以0结尾的指针数组。。 { printf("%s\t", row[i]); } printf("\n"); } } int main() { int ret = 0, status = 0; MYSQL *mysql; MYSQL_RES *result; MYSQL_ROW row; char *query; mysql = mysql_init(NULL); mysql =mysql_real_connect(mysql, "localhost", "root", "123456", "mydb2", 0, NULL, CLIENT_MULTI_STATEMENTS); if (mysql == NULL) { ret = mysql_errno(mysql); printf("func mysql_real_connect() err\n"); return ret; } else { printf(" ok......\n"); } /* execute multiple statements */ status = mysql_query(mysql, "DROP TABLE IF EXISTS test_table;\ CREATE TABLE test_table(id INT);\ INSERT INTO test_table VALUES(10);\ UPDATE test_table SET id=20 WHERE id=10;\ SELECT * FROM test_table;\ DROP TABLE test_table"); if (status) { printf("Could not execute statement(s)"); mysql_close(mysql); exit(0); } /* process each statement result */ do { /* did current statement return data? */ result = mysql_store_result(mysql); if (result) { /* yes; process rows and free the result set */ process_result_set(mysql, result); mysql_free_result(result); } else /* no result set or error */ { if (mysql_field_count(mysql) == 0) { printf("%lld rows affected\n", mysql_affected_rows(mysql)); } else /* some error occurred */ { printf("Could not retrieve result set\n"); break; } } /* more results? -1 = no, >0 = error, 0 = yes (keep looping) */ if ((status = mysql_next_result(mysql)) > 0) printf("Could not execute statement\n"); } while (status == 0); mysql_close(mysql); }
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