[数据库]_[初级]_[sqlite3简单使用]

场景

1.sqlite3在很多小型项目都会用到, 比如用来存储Android的联系人，短信等. 这个小巧的sqlite3是文件型的数据库, 也方便做配置文件和程序打包. 使用sql查询也方面. 所以sqlite3在非结构化数据时比xml来的方便, 高效,省空间.

2.在移动开发盛行的年代, sqlite3是必备的技术了.

说明

1.以下是sqlite3常见的增删改查操作和一些注意事项.

2.比json,xml文件更小更容易查询, 可以使用软件SqliteBrowser来管理DB. 麻烦就是不能使用文本编辑器直接查看. 建议用于比较多的设置选项保存.

3.sqlite3是开源的数据库, 代码质量很高, 阅读源码也可以从中学到很多东西. 用C写代码的话有个缺点就是在增量打开资源时, 每次如果if条件不成立也需要按顺序释放. 可以使用C++的特性 std::shared_ptr 解决.

例子

#include "gtest/gtest.h"

#include <Windows.h>
#include <memory>
#include "sqlite3.h"

using namespace std;

static int PCallback(void* data,int argc,char** argv,char** err)
{
    auto count = (int*)data;
    *count = atoi(argv[0]);
    return 0;
}

bool TestSqlite3Api()
{

    sqlite3* db = NULL;
    sqlite3_stmt* query = NULL;
    int ret = 0;

    // 创建DB文件
    // 如果不需要创建db文件,使用sqlite3_open即可
    ret = sqlite3_open_v2("test.db",&db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, NULL);
    if (SQLITE_OK != ret)
        return false;

    std::shared_ptr<sqlite3> sp_db(db,[](sqlite3* db)
    {
        std::cout << "sqlite3_close" << std::endl;
        sqlite3_close(db);
    });

    // 创建表
    std::string create = "CREATE TABLE IF NOT EXISTS items (userid INTEGER PRIMARY KEY, ipaddr"
    " TEXT,username TEXT,useradd TEXT,userphone INTEGER,age INTEGER, "
                                                    "time TEXT NOT NULL DEFAULT"
                                                                             " (NOW()));";
    // 注意,如果使用了sqlite3_stmt不关闭的话调用sqlite3_close是返回 SQLITE_BUSY 失败的.
    sqlite3_stmt *create_stmt = NULL;
    ret = sqlite3_prepare(db, create.c_str(), create.size(), &create_stmt, NULL);
    if(SQLITE_OK != ret)
        return false;

    std::shared_ptr<sqlite3_stmt> create_sp(create_stmt,[](sqlite3_stmt* stmt)
    {
        std::cout << "sqlite3_finalize create_stmt" << std::endl;
        sqlite3_finalize(stmt);
    });
    if (sqlite3_step(create_stmt) != SQLITE_DONE)
        return false;

    // 插入表数据
    string insert = "INSERT INTO items (time, ipaddr,username,useradd,userphone,age) "
        "VALUES ('7:30', '192.187.27.55','vivekanand','kolkatta','04456823948',74);"; // WORKS!
    sqlite3_stmt *insert_stmt = NULL;
    ret = sqlite3_prepare(db, insert.c_str(), insert.size(), &insert_stmt, NULL);
    if(SQLITE_OK != ret)
        return false;

    std::shared_ptr<sqlite3_stmt> insert_sp(insert_stmt,[](sqlite3_stmt* stmt)
    {
        std::cout << "sqlite3_finalize insert_stmt" << std::endl;
        sqlite3_finalize(stmt);
    });
    ret = sqlite3_step(insert_stmt);
    if (ret != SQLITE_DONE)
        return false;

    // 查询表数据
    string select = "select count(0) from items;";
    sqlite3_stmt *select_stmt = NULL;
    ret = sqlite3_prepare(db, select.c_str(), select.size(), &select_stmt, NULL);
    if(SQLITE_OK != ret)
        return false;

    std::shared_ptr<sqlite3_stmt> select_sp(select_stmt,[](sqlite3_stmt* stmt)
    {
        std::cout << "sqlite3_finalize selectStmt" << std::endl;
        sqlite3_finalize(stmt);
    });

    //1. 查询方式1
    ret = sqlite3_step(select_stmt);
    int count = 0;
    while(ret == SQLITE_ROW )
    {
        count+= sqlite3_column_int(select_stmt,0);
        break;
    }
    std::cout << "frist select count: " << count << std::endl;

    //2. 查询方式2
    count = 0;
    ret = sqlite3_exec(db,"select count(0) from items;",PCallback,&count,NULL);
    if(ret != SQLITE_OK)
        return false;

    std::cout << "second select count: " << count << std::endl;
    return true;
}

TEST(test_sqlite3,TestSqlite3)
{
    ASSERT_TRUE(TestSqlite3Api(),SQLITE_OK);
}

输出

Note: Google Test filter = test_sqlite3.TestSqlite3
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from test_sqlite3
[ RUN      ] test_sqlite3.TestSqlite3
frist select count: 1
second select count: 1
sqlite3_finalize selectStmt
sqlite3_finalize insert_stmt
sqlite3_finalize create_stmt
sqlite3_close
[       OK ] test_sqlite3.TestSqlite3 (296 ms)
[----------] 1 test from test_sqlite3 (312 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (328 ms total)

参考

SQLite C/C++ Tutorial

C-language Interface Specification for SQLite

An Introduction To The SQLite C/C++ Interface

quickstart