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分类: SQLite/嵌入式数据库

2011-11-29 13:23:51

这几天遇到了一个问题就是在insert以及update数据的时候,总是生成一个.db-journal文件,重新启动程序后,该文件消失,前面添加修改的数据没有成功保存。关于如何解决这个问题,网上也没有人给出详细答案,但经过几天的分析,试验,最后成功了。不知道对所有出现的这个问题都能应付的过来,解决的方法很简单,如下:

程序中使用了

sqlite3_stmt *stmt;

然后通过rc = sqlite3_prepare(db, sql, strlen(sql), &stmt, &tail);将sql语句解析到stmt中,然后对数据库操作完成之后,没有释放stmt,当我调用sqlite3_finalize(stmt);将stmt释放之后,上面的问题不在出现了。

对此sqlite中还有一对匹配的用法。如下:

sqlite3_get_table( db , sql , &azResult , &nrow , &ncolumn , &zErrMsg );

sqlite3_free_table( azResult );

 

下面是一些sql语句的用法。

sprintf(sql, "INSERT INTO \"Phonebook\" VALUES((select min(ID)-1 from Phonebook where ID>1 and ID-1 not in (select ID from Phonebook)), \'%s\', \'%s\');", p->list[1], p->list[2]);

 

 char sql1[100];
sprintf(sql1, "select * from Phonebook where Username like \'%s%%\'order by Username;", buffer);

上面是关于like匹配的用法,Username like '王%'   以及 Username like '王_' ,%用来匹配任意字符,_用来匹配一个字符。而且还要注意的是,c语言中 %的转义方式是%%,而不是\%

 

上面一句话是从csdn上问的结果,插入的数据,是按照ID号从小的开始插入。也就是将中间的空缺补上

#include
#include
#include "sqlite3.h"
#define _DEBUG_

int main( void )
{
sqlite3 *db=NULL;
char *zErrMsg = 0;

int rc;

///open(create) database
rc = sqlite3_open("phonebook.db", &db);
if( rc )
{
fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
sqlite3_close(db);
return 0;
}
else printf("You have opened a sqlite3 database named zieckey.db successfully!\nCongratulations! Have fun ! ^-^ \n");

///create table
char *sql = " CREATE TABLE Call_Record(\
      Status CHAR(10),\
      Username VARCHAR(20),\
      Phonenubmer VARCHAR(20),\
      Time timestamp,\
      PRIMARY KEY (Status, Username)\
      );" ;

//上面一句用来定义两个主键
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

///create table2
sql = " CREATE TABLE Phonebook(\
      Username VARCHAR(20) PRIMARY KEY,\
      Phonenubmer VARCHAR(20)\
      );" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );


///insert database
sql = "INSERT INTO \"Call_Record\" VALUES('missed', 'Tom', '15908079860',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('answered', 'Jack', '15908079861',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('dialed','Merry', '15908079863',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('dialed', 'Zjf', '15908079864',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('dialed', 'Qcx', '15908079865',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('dialed', 'MM', '15908079866',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('answered', 'JJ', '15908079867',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('answered', 'GG', '15908079868',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('answered', 'DD', '15908079869',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('answered', 'Father', '15908079870',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Call_Record\" VALUES('missed', 'Mather', '15908079871',datetime('now','localtime'));" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

///insert database table two
sql = "INSERT INTO \"Phonebook\" VALUES('Tom', '15908079860');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('Jack', '15908079861');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('Merry', '15908079863');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('Zjf', '15908079864');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('Qcx', '15908079865');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('MM', '15908079866');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('JJ', '15908079867');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('GG', '15908079868');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('DD', '15908079869');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('Father', '15908079870');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

sql = "INSERT INTO \"Phonebook\" VALUES('Mather', '15908079871');" ;
sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

int nrow = 0, ncolumn = 0;
char **azResult;

///select database
sql = "SELECT * FROM Call_Record ";

//sql = "select * from Phonebook order by Username";   //默认为升序asc

//sql = "select * from Phonebook order by Username desc";   //降序

//sql = "select * from Phonebook order by (case Username when \"\" then \'zzzzz\' else Username end);";

//sql = "select * from Phonebook order by (case Username when null then \'zzzzz\' else Username end);";

//上面一句是处理空值情况(null 与""),sqlserver默认空值为最小,使用case可以改变它查询的值。
sqlite3_get_table( db , sql , &azResult , &nrow , &ncolumn , &zErrMsg );
int i = 0 ;
printf( "row:%d column=%d \n" , nrow , ncolumn );
printf( "\nThe result of querying is : \n" );
for( i=0 ; i<( nrow + 1 ) * ncolumn ; i++ )
printf( "azResult[%d] = %s\n", i , azResult[i] );

///select database
sql = "SELECT * FROM Phonebook ";
sqlite3_get_table( db , sql , &azResult , &nrow , &ncolumn , &zErrMsg );
printf( "row:%d column=%d \n" , nrow , ncolumn );
printf( "\nThe result of querying is : \n" );
for( i=0 ; i<( nrow + 1 ) * ncolumn ; i++ )
printf( "azResult[%d] = %s\n", i , azResult[i] );
/*
///delete database
sql = "DELETE FROM Call_Record WHERE Username = \'GG\' ;" ;

sqlite3_exec( db , sql , 0 , 0 , &zErrMsg );

///update database
char sql1[100];
sprintf(sql1,"UPDATE Call_Record SET Phonenubmer = \'%s\' WHERE Username = \'%s\'", "10111", "MM");

sqlite3_exec( db , sql1 , 0 , 0 , &zErrMsg );
*/
///select database desc (jiangxupailie)
///if no desc is default(asc)
sql = "SELECT * FROM Call_Record order by Username desc";
sqlite3_get_table( db , sql , &azResult , &nrow , &ncolumn , &zErrMsg );
printf( "\n\n\n\nrow:%d column=%d " , nrow , ncolumn );
printf( "\nAfter deleting , the result of querying is : \n" );
for( i=0 ; i<( nrow + 1 ) * ncolumn ; i++ )
printf( "azResult[%d] = %s\n", i , azResult[i] );


///free azResult
sqlite3_free_table( azResult );

///close db
sqlite3_close(db);
return 0;

}

另外一种查询获取列值的方法:

            int i, j, rc, ncols;
            char *sql;
            char *tail;
            char buff[100];
            sqlite3_stmt *stmt;

            ///about dababase select
            sql = "select * from Phonebook order by (case Username when \"\" then \'zzzzz\' else Username end);";
            rc = sqlite3_prepare(db, sql, strlen(sql), &stmt, &tail);
            if (rc !=SQLITE_OK)
            {
                break;
            }
            rc = sqlite3_step(stmt);                      //取得数据表中一行的数据
            ncols = sqlite3_column_count(stmt);  //获取数据表有多少列
            while(rc==SQLITE_ROW) {
                for (j = 0; j < ncols; j++){
                    sprintf(buff,"%s",sqlite3_column_text(stmt, j)); //获取一行中每一列的数据
                    printf("%s\n",buff);
                }
                rc= sqlite3_step(stmt);            //获取下一行数据
            }

            sqlite3_finalize(stmt);

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