sqlite 链接
#include <sqlite3.h> #include <string> #include <stdio.h> using namespace std; void doTest() { sqlite3* conn = NULL; //1. 打开数据库 int result = sqlite3_open("D:/mytest.db",&conn); if (result != SQLITE_OK) { sqlite3_close(conn); return; } const char* createTableSQL = "CREATE TABLE TESTTABLE (int_col INT,float_col REAL,string_col TEXT)"; sqlite3_stmt* stmt = NULL; int len = strlen(createTableSQL); //2. 准备创建数据表,如果创建失败,需要用sqlite3_finalize释放sqlite3_stmt对象,以防止内存泄露。 if (sqlite3_prepare_v2(conn,createTableSQL,len,&stmt,NULL) != SQLITE_OK) { if (stmt) sqlite3_finalize(stmt); sqlite3_close(conn); return; } //3. 通过sqlite3_step命令执行创建表的语句。对于DDL和DML语句而言,sqlite3_step执行正确的返回值 //只有SQLITE_DONE,对于SELECT查询而言,如果有数据返回SQLITE_ROW,当到达结果集末尾时则返回 //SQLITE_DONE。 if (sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); sqlite3_close(conn); return; } //4. 释放创建表语句对象的资源。 sqlite3_finalize(stmt); printf("Succeed to create test table now.n"); int insertCount = 10; //5. 构建插入数据的sqlite3_stmt对象。 const char* insertSQL = "INSERT INTO TESTTABLE VALUES(%d,%f,'%s')"; const char* testString = "this is a test."; char sql[1024]; sqlite3_stmt* stmt2 = NULL; for (int i = 0; i < insertCount; ++i) { sprintf(sql,insertSQL,i,i * 1.0,testString); if (sqlite3_prepare_v2(conn,sql,strlen(sql),&stmt2,NULL) != SQLITE_OK) { if (stmt2) sqlite3_finalize(stmt2); sqlite3_close(conn); return; } if (sqlite3_step(stmt2) != SQLITE_DONE) { sqlite3_finalize(stmt2); sqlite3_close(conn); return; } printf("Insert Succeed.n"); } sqlite3_finalize(stmt2); //6. 为了方便下一次测试运行,我们这里需要删除该函数创建的数据表,否则在下次运行时将无法 //创建该表,因为它已经存在。 const char* dropSQL = "DROP TABLE TESTTABLE"; sqlite3_stmt* stmt3 = NULL; if (sqlite3_prepare_v2(conn,dropSQL,strlen(dropSQL),&stmt3,NULL) != SQLITE_OK) { if (stmt3) sqlite3_finalize(stmt3); sqlite3_close(conn); return; } if (sqlite3_step(stmt3) == SQLITE_DONE) { printf("The test table has been dropped.n"); } sqlite3_finalize(stmt3); sqlite3_close(conn); } int main() { doTest(); return 0; } //输出结果如下: //Succeed to create test table now. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //The test table has been dropped.
#include <sqlite3.h> #include <string> using namespace std; void doTest() { sqlite3* conn = NULL; //1. 打开数据库 int result = sqlite3_open("D:/mytest.db",NULL) != SQLITE_OK) { if (stmt) sqlite3_finalize(stmt); sqlite3_close(conn); return; } //3. 通过sqlite3_step命令执行创建表的语句。对于DDL和DML语句而言,sqlite3_step执行正确的返回值 //只有SQLITE_DONE,对于SELECT查询而言,如果有数据返回SQLITE_ROW,当到达结果集末尾时则返回 //SQLITE_DONE。 if (sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); sqlite3_close(conn); return; } //4. 释放创建表语句对象的资源。 sqlite3_finalize(stmt); printf("Succeed to create test table now.n"); //5. 构造查询表数据的sqlite3_stmt对象。 const char* selectSQL = "SELECT * FROM TESTTABLE WHERE 1 = 0"; sqlite3_stmt* stmt2 = NULL; if (sqlite3_prepare_v2(conn,selectSQL,strlen(selectSQL),NULL) != SQLITE_OK) { if (stmt2) sqlite3_finalize(stmt2); sqlite3_close(conn); return; } //6. 根据select语句的对象,获取结果集中的字段数量。 int fieldCount = sqlite3_column_count(stmt2); printf("The column count is %d.n",fieldCount); //7. 遍历结果集中每个字段meta信息,并获取其声明时的类型。 for (int i = 0; i < fieldCount; ++i) { //由于此时Table中并不存在数据,再有就是SQLite中的数据类型本身是动态的,所以在没有数据时 //无法通过sqlite3_column_type函数获取,此时sqlite3_column_type只会返回SQLITE_NULL, //直到有数据时才能返回具体的类型,因此这里使用了sqlite3_column_decltype函数来获取表声 //明时给出的声明类型。 string stype = sqlite3_column_decltype(stmt2,i); stype = strlwr((char*)stype.c_str()); //下面的解析规则见该系列的“数据类型-->1. 决定字段亲缘性的规则”部分,其链接如下: //http://www.cnblogs.com/stephen-liu74/archive/2012/01/18/2325258.html if (stype.find("int") != string::npos) { printf("The type of %dth column is INTEGER.n",i); } else if (stype.find("char") != string::npos || stype.find("text") != string::npos) { printf("The type of %dth column is TEXT.n",i); } else if (stype.find("real") != string::npos || stype.find("floa") != string::npos || stype.find("doub") != string::npos ) { printf("The type of %dth column is DOUBLE.n",i); } } sqlite3_finalize(stmt2); //8. 为了方便下一次测试运行,我们这里需要删除该函数创建的数据表,否则在下次运行时将无法 //创建该表,因为它已经存在。 const char* dropSQL = "DROP TABLE TESTTABLE"; sqlite3_stmt* stmt3 = NULL; if (sqlite3_prepare_v2(conn,NULL) != SQLITE_OK) { if (stmt3) sqlite3_finalize(stmt3); sqlite3_close(conn); return; } if (sqlite3_step(stmt3) == SQLITE_DONE) { printf("The test table has been dropped.n"); } sqlite3_finalize(stmt3); sqlite3_close(conn); } int main() { doTest(); return 0; } //输出结果为: //Succeed to create test table now. //The column count is 3. //The type of 0th column is INTEGER. //The type of 1th column is DOUBLE. //The type of 2th column is TEXT. //The test table has been dropped.
#include <sqlite3.h> #include <string> #include <stdio.h> using namespace std; void doTest() { sqlite3* conn = NULL; //1. 打开数据库 int result = sqlite3_open("D:/mytest.db",NULL) != SQLITE_OK) { if (stmt) sqlite3_finalize(stmt); sqlite3_close(conn); return; } //3. 通过sqlite3_step命令执行创建表的语句。对于DDL和DML语句而言,sqlite3_step执行正确的返回值 //只有SQLITE_DONE,对于SELECT查询而言,如果有数据返回SQLITE_ROW,当到达结果集末尾时则返回 //SQLITE_DONE。 if (sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); sqlite3_close(conn); return; } //4. 释放创建表语句对象的资源。 sqlite3_finalize(stmt); printf("Succeed to create test table now.n"); //5. 显式的开启一个事物。 sqlite3_stmt* stmt2 = NULL; const char* beginSQL = "BEGIN TRANSACTION"; if (sqlite3_prepare_v2(conn,beginSQL,strlen(beginSQL),NULL) != SQLITE_OK) { if (stmt2) sqlite3_finalize(stmt2); sqlite3_close(conn); return; } if (sqlite3_step(stmt2) != SQLITE_DONE) { sqlite3_finalize(stmt2); sqlite3_close(conn); return; } sqlite3_finalize(stmt2); //6. 构建基于绑定变量的插入数据。 const char* insertSQL = "INSERT INTO TESTTABLE VALUES(?,?,?)"; sqlite3_stmt* stmt3 = NULL; if (sqlite3_prepare_v2(conn,strlen(insertSQL),NULL) != SQLITE_OK) { if (stmt3) sqlite3_finalize(stmt3); sqlite3_close(conn); return; } int insertCount = 10; const char* strData = "This is a test."; //7. 基于已有的SQL语句,迭代的绑定不同的变量数据 for (int i = 0; i < insertCount; ++i) { //在绑定时,最左面的变量索引值是1。 sqlite3_bind_int(stmt3,1,i); sqlite3_bind_double(stmt3,2,i * 1.0); sqlite3_bind_text(stmt3,3,strData,strlen(strData),SQLITE_TRANSIENT); if (sqlite3_step(stmt3) != SQLITE_DONE) { sqlite3_finalize(stmt3); sqlite3_close(conn); return; } //重新初始化该sqlite3_stmt对象绑定的变量。 sqlite3_reset(stmt3); printf("Insert Succeed.n"); } sqlite3_finalize(stmt3); //8. 提交之前的事物。 const char* commitSQL = "COMMIT"; sqlite3_stmt* stmt4 = NULL; if (sqlite3_prepare_v2(conn,commitSQL,strlen(commitSQL),&stmt4,NULL) != SQLITE_OK) { if (stmt4) sqlite3_finalize(stmt4); sqlite3_close(conn); return; } if (sqlite3_step(stmt4) != SQLITE_DONE) { sqlite3_finalize(stmt4); sqlite3_close(conn); return; } sqlite3_finalize(stmt4); //9. 为了方便下一次测试运行,我们这里需要删除该函数创建的数据表,否则在下次运行时将无法 //创建该表,因为它已经存在。 const char* dropSQL = "DROP TABLE TESTTABLE"; sqlite3_stmt* stmt5 = NULL; if (sqlite3_prepare_v2(conn,&stmt5,NULL) != SQLITE_OK) { if (stmt5) sqlite3_finalize(stmt5); sqlite3_close(conn); return; } if (sqlite3_step(stmt5) == SQLITE_DONE) { printf("The test table has been dropped.n"); } sqlite3_finalize(stmt5); sqlite3_close(conn); } int main() { doTest(); return 0; } //输出结果如下: //Succeed to create test table now. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //Insert Succeed. //The test table has been dropped.
#include <sqlite3.h> #include <string> #include <stdio.h> using namespace std; void doTest() { sqlite3* conn = NULL; //1. 打开数据库 int result = sqlite3_open("D:/mytest.db",NULL) != SQLITE_OK) { if (stmt) sqlite3_finalize(stmt); sqlite3_close(conn); return; } //3. 通过sqlite3_step命令执行创建表的语句。对于DDL和DML语句而言,sqlite3_step执行正确的返回值 //只有SQLITE_DONE,对于SELECT查询而言,如果有数据返回SQLITE_ROW,当到达结果集末尾时则返回 //SQLITE_DONE。 if (sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); sqlite3_close(conn); return; } //4. 释放创建表语句对象的资源。 sqlite3_finalize(stmt); printf("Succeed to create test table now.n"); //5. 为后面的查询操作插入测试数据。 sqlite3_stmt* stmt2 = NULL; const char* insertSQL = "INSERT INTO TESTTABLE VALUES(20,21.0,'this is a test.')"; if (sqlite3_prepare_v2(conn,NULL) != SQLITE_OK) { if (stmt2) sqlite3_finalize(stmt2); sqlite3_close(conn); return; } if (sqlite3_step(stmt2) != SQLITE_DONE) { sqlite3_finalize(stmt2); sqlite3_close(conn); return; } printf("Succeed to insert test data.n"); sqlite3_finalize(stmt2); //6. 执行SELECT语句查询数据。 const char* selectSQL = "SELECT * FROM TESTTABLE"; sqlite3_stmt* stmt3 = NULL; if (sqlite3_prepare_v2(conn,NULL) != SQLITE_OK) { if (stmt3) sqlite3_finalize(stmt3); sqlite3_close(conn); return; } int fieldCount = sqlite3_column_count(stmt3); do { int r = sqlite3_step(stmt3); if (r == SQLITE_ROW) { for (int i = 0; i < fieldCount; ++i) { //这里需要先判断当前记录当前字段的类型,再根据返回的类型使用不同的API函数 //获取实际的数据值。 int vtype = sqlite3_column_type(stmt3,i); if (vtype == SQLITE_INTEGER) { int v = sqlite3_column_int(stmt3,i); printf("The INTEGER value is %d.n",v); } else if (vtype == SQLITE_FLOAT) { double v = sqlite3_column_double(stmt3,i); printf("The DOUBLE value is %f.n",v); } else if (vtype == SQLITE_TEXT) { const char* v = (const char*)sqlite3_column_text(stmt3,i); printf("The TEXT value is %s.n",v); } else if (vtype == SQLITE_NULL) { printf("This value is NULL.n"); } } } else if (r == SQLITE_DONE) { printf("Select Finished.n"); break; } else { printf("Failed to SELECT.n"); sqlite3_finalize(stmt3); sqlite3_close(conn); return; } } while (true); sqlite3_finalize(stmt3); //7. 为了方便下一次测试运行,我们这里需要删除该函数创建的数据表,否则在下次运行时将无法 //创建该表,因为它已经存在。 const char* dropSQL = "DROP TABLE TESTTABLE"; sqlite3_stmt* stmt4 = NULL; if (sqlite3_prepare_v2(conn,NULL) != SQLITE_OK) { if (stmt4) sqlite3_finalize(stmt4); sqlite3_close(conn); return; } if (sqlite3_step(stmt4) == SQLITE_DONE) { printf("The test table has been dropped.n"); } sqlite3_finalize(stmt4); sqlite3_close(conn); } int main() { doTest(); return 0; } //输出结果如下: //Succeed to create test table now. //Succeed to insert test data. //The INTEGER value is 20. //The DOUBLE value is 21.000000. //The TEXT value is this is a test.. //Select Finished. //The test table has been dropped.
callback函数 sqlite3* db; int rc; char* zErr; rc = sqlite3_open("test.db,&db); if(rc) cout<<"ERROR"<<endl; char * data = "CallBack"; char * sql = "select * from test"; rc = sqlite3_exec( db,callback,data,&zErr ); if( rc != SQLITE_OK) cout<<"ERROR"<<endl; sqlite3_close(db);
int callback(void* data,int ncols,char**values,char** headers) { for( int i=0; i<ncols; i++) cout << headers[i] <<" --> "<< values[i] <<endl; } 对sqlite3_exec执行结果中查询到的每条记录应用callback函数 每条记录的相应字段值存放于values数组,表头存放于headers数组,可以完成相应数据处理
sqlite3_get_table查询 char ** result; int nrows,ncols; char * zErr; char * sql = "select * from test;"; int rc = sqlite3_get_table( db,&result,&nrows,&ncols,&zErr ); cout<<"行数: "<< nrows<<endl; cout<<"列数: "<< ncols<<endl; for( int i = 0; i <= nrows; i++ ) { for( int j = 0; j < ncols; j++ ) cout<< result[i*ncols+j] <<"t"; cout<<endl; } sqlite3_free_table(result); sqlite3_get_table 将查询得到的结果全部存入result数组,并可得到行数和列数 注意,第一行是表头
预处理查询
int rc; sqlite3 *db; sqlite3_stmt *stmt; char *sql = "select * from episodes;"; const char *tail; rc = sqlite3_open("test.db",&db); rc = sqlite3_prepare(db,(int)strlen(sql),&tail); rc = sqlite3_step(stmt); int ncols = sqlite3_column_count(stmt); while(rc == SQLITE_ROW) //sqlite3_step() has another row ready #define SQLITE_ROW 100 { for( int i=0; i < ncols; i++ ) cout <<sqlite3_column_text(stmt,i); cout << endl ; rc =sqlite3_step(stmt); } sqlite3_finalize(stmt); sqlite3_close(db);
sqlite3_prepare()也能接受一个包括多个SQL语句的字符串,但是只处理第一个SQL 若想处理多个,可应用tail参数,如下
while( sqlite3_complete(sql) ) { rc = sqlite3_prepare(db,&tail); sql = tail; ........... } 取字段信息 sqlite3_stmt * : statement handle int iConl : 列号 const char *sqlite3_column_name( sqlite3_stmt*,int iCol ); //获取字段名称
const char *sqlite3_database_name( sqlite3_stmt*,int iCol ); //获取数据库名称 const char *sqlite3_table_name( sqlite3_stmt*,int iCol ); //获取表的名称
intsqlite3_column_type( sqlite3_stmt*,int iCol ); //SQLite本身的类型,或称存储类 返回值说明 1:SQLITE_INTEGER 2:SQLITE_FLOAT 3:SQLITE_TEXT 4:SQLITE_BLOB 5:SQLITE_NULL
const char *sqlite3_column_decltype( sqlite3_stmt*,int iCol ); //字段声明时的类型 如果结果集中的一列不是来自一个实际的字段(如来自于表达式、函数或聚合的结果),这个函数将返回NULL
sqlite3_column_xxx()函数取当前记录中每个字段的值
xxx表示你希望得到的数据类型,包括以下函数: int sqlite3_column_int(sqlite3_stmt*,intiCol); double sqlite3_column_double(sqlite3_stmt*,int iCol); long long int sqlite3_column_int64(sqlite3_stmt*,int iCol); const void*sqlite3_column_blob(sqlite3_stmt*,int iCol); const unsigned char*sqlite3_column_text(sqlite3_stmt*,int iCol); const void*sqlite3_column_text16(sqlite3_stmt*,int iCol); (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |