使用正则表达式解析一般sql语句（C++）

趁这个时候把之前写过的代码都贴上来吧。
正则表达式一用，整个人都感觉神清气爽了，会了正则表达式，表示字符串解析什么的，顿时轻松了不少啊。不过C和C++现存的大部分编译器是不支持正则表达式的，最新出来的C++10标准（貌似是C++10）中新加入了正则表达式，但是支持最新标准的编译器较少，VS最新版本的应该是支持的。不过博主一直对CodeBlocks情有独钟，忠心不二啊。这就得给编译器装boost函数库了， 这是一项浩大且繁琐的工程，以至于现在想想都会痛哭流涕，当时装了一整天，失败了好多次才装好。
如果你时间实在紧迫，或则怕麻烦，那博主还是建议你使用VS或则放弃C++,C投靠JAVA吧，JAVA中可以直接使用正则表达式很方便的。怎么安装正则表达式我就不详细说了，你得先去boost官网下载boost函数库，然后安装到电脑，最后还得配置到编译器上。有很多详细的介绍，还麻烦大家查一查。
当然，安装好boost库后还得学一学怎么使用正则表达式，正则表达式是有单独的语法的，不过不难，几个小时就能学会吧，给大家推荐一个链接，里面介绍得很详细http://www.jb51.net/tools/zhengze.html
学好了之后就可以应用了，其实之前写的计算器如果用正则表达式可能会方便很多，这里用正则表达式来解析部分的SQL语句，不过只是较为简单的形式，不支持复杂形式如语句嵌套。

C++代码，这个没有代码注释的习惯我以后一定改….另外，如果大家运行不成功，可能是main函数出了问题，因为main函数之前有修改过，其他两个文件是不会有问题的

//头文件，语句解析类#ifndef SQLEXPRESSION_H_INCLUDED#define SQLEXPRESSION_H_INCLUDED#include <string.h>#include <vector>#include <boost/regex.hpp>#include<algorithm>#include<iostream>using namespace std;using namespace boost;class SqlEx{public:    SqlEx(string ex);    ~SqlEx();    bool check();    vector<vector<string>> getResult();private:    bool ForUpdate();    bool ForDelete();    bool ForInsert();    bool ForCreate();    bool ForSelect();    bool ForDrop();    string sql(string str);    vector<vector<string>> result;    string Ex;};#endif // SQLEXPRESSION_H_INCLUDED

#include <fstream>#include "SQLexpression.h"using namespace std;using namespace boost;SqlEx::SqlEx(string ex){    Ex = ex;}SqlEx::~SqlEx(){    //delete Vresults;}bool SqlEx::check(){    transform(Ex.begin(),Ex.end(),Ex.begin(),towlower);    Ex=sql(Ex);    Ex=Ex+"END";    string sqlupdate="update\.+set\.+(where\.+)?END";    string sqldelete="delete\.+from\.+where\.+END";    string sqlinsert="insert\.+into\.+(\(\.+/)\.*)?values\(.+\)END";    string sqlcreate="create table\.+\\(\.+\\)END";    string sqlselect="select\.+from\.+(where\.+)?((group by)?|(order by)?|(having)?)END";    string sqldrop  ="drop table\.+END";    regex Pupdate(sqlupdate);    regex Pdelete(sqldelete);    regex Pinsert(sqlinsert);    regex Pcreate(sqlcreate);    regex Pselect(sqlselect);    regex Pdrop(sqldrop);    if(regex_match(Ex,Pupdate)){       return  ForUpdate();    }    else if(regex_match(Ex,Pdelete)){       return  ForDelete();    }    else if(regex_match(Ex,Pinsert)){        return ForInsert();    }    else if(regex_match(Ex,Pcreate)){        return ForCreate();    }    else if(regex_search(Ex,Pselect)){        return ForSelect();    }    else if(regex_match(Ex,Pdrop)){        return ForDrop();    }    else{            cout<<"请检查你的语句是否正确，不支持该语句！！"<<endl;            return false;    }    return true;}bool SqlEx::ForUpdate(){    vector<vector<string>> Vupdate;    string str[3];    smatch sm[3];    regex re1("(?<=update )\.+(?= set)");    regex re2("((?<=set )\.+(?= where))|((?<=set )\.+(?=END))");    regex re3("(?<=where )\.+(?=END)");    if(regex_search(Ex,sm[0],re1)){        vector<string>update1;        str[0]=sm[0].str();        update1.push_back(str[0]);        cout<<"update:"<<endl;        cout<<str[0]<<endl;        cout<<endl;        Vupdate.push_back(update1);    }else{        cout<<"请检查update与set语句间是否存在错误!!"<<endl;        return false;    }    if(regex_search(Ex,sm[1],re2)){            vector<string>update2;        str[1]=sm[1].str();         update2.push_back(str[1]);         cout<<"set:"<<endl;        cout<<str[1]<<endl;        cout<<endl;    Vupdate.push_back(update2);    }else{        cout<<"请检查set字段是否存在错误！！"<<endl;        return false;    }    if(regex_search(Ex,sm[2],re3)){        vector<string>update3;        cout<<"where:"<<endl;        str[2]=sm[2].str();        regex rr("(\.+?and )|(\.+?or )");        smatch rrsm;        string::const_iterator st=str[2].begin();        string::const_iterator en=str[2].end();        bool flag=false;        while(regex_search(st,en,rrsm,rr)){            flag =true;            cout<<rrsm.str()<<endl;            update3.push_back(rrsm.str());            st=rrsm[0].second;        }        if(flag){                regex_search(st,en,rrsm,regex("\.+"));                cout<<rrsm.str()<<endl;                update3.push_back(rrsm.str());        }        else{                cout<<str[2]<<endl;                update3.push_back(str[2]);        }        Vupdate.push_back(update3);    }    result=Vupdate;    return true;}bool SqlEx::ForDelete(){    vector<vector<string>> Vdelete;    regex re1("(?<=delete from )\.+(?=where )");    regex re2("(?<=where )\.+(?=END)");    string dstr[2];    smatch dsm[2];    string::const_iterator st = Ex.begin();    string::const_iterator en = Ex.end();    if(regex_search(Ex,dsm[0],re1)){        vector<string>vdelete1;        dstr[0]=dsm[0].str();        vdelete1.push_back(dstr[0]);        cout<<"delete from:"<<endl;        cout<<dstr[0]<<endl;        cout<<endl;        Vdelete.push_back(vdelete1);    }else{        cout<<"检查delete from与where之间是否存在错误"<<endl;    }    if(regex_search(Ex,dsm[1],re2)){        vector<string>vdelete1;        cout<<"where:"<<endl;        dstr[1]=dsm[1].str();        regex rr("(\.+?and )|(\.+?or )");        smatch rrsm;        string::const_iterator st=dstr[1].begin();        string::const_iterator en=dstr[1].end();        bool flag=false;        while(regex_search(st,en,rrsm,rr)){            flag =true;            cout<<rrsm.str()<<endl;            vdelete1.push_back(rrsm.str());            st=rrsm[0].second;        }        if(flag){                regex_search(st,en,rrsm,regex("\.+"));                cout<<rrsm.str()<<endl;                vdelete1.push_back(rrsm.str());        }        else{                cout<<dstr[1]<<endl;            vdelete1.push_back(dstr[1]);        }        Vdelete.push_back(vdelete1);    }else{        cout<<"检查where语句后是否存在错误！！"<<endl;    }    result=Vdelete;    return true;}bool SqlEx::ForInsert(){    vector<vector<string>> Vinsert;    regex re1("(?<=insert into )\.+(?=values)");    regex re2("(?<=values\\()\.+(?=\\)END)");    string istr[2];    smatch ism[2];    if(regex_search(Ex,ism[0],re1)){        vector<string>vinsert1;        istr[0]=ism[0].str();        regex rr("(?<=\\()\.+(?=\\))");        smatch rsm;         cout<<"Insert into:"<<endl;        if(regex_search(istr[0],rsm,rr)){            regex rr2("\.+?(?=\\()");            smatch rsm2;            regex_search(istr[0],rsm2,rr2);            cout<<rsm2.str()<<endl;            cout<<endl;            vinsert1.push_back(rsm2.str());            string rstr=rsm.str();            smatch rsm1;            regex rr1("(?<=')\.+?(?=')") ;            string::const_iterator st=rstr.begin();            string::const_iterator en=rstr.end();            while(regex_search(st,en,rsm1,rr1)){                if(rsm1.str()!=","){                    cout<<rsm1.str()<<endl;                    vinsert1.push_back(rsm1.str());                }                st=rsm1[0].second;            }        }else{                vinsert1.push_back(istr[0]);                cout<<istr[0]<<endl;        }        Vinsert.push_back(vinsert1);        cout<<endl;    }else{        cout<<"检查insert into语句后是否存在错误！！！"<<endl;        return false;    }    if(regex_search(Ex,ism[1],re2)){            vector<string>vinsert2;        istr[1]=ism[1].str();        cout<<"Values:"<<endl;        smatch rsm3;        regex rr3("(?<=')\.+?(?=')") ;        string::const_iterator st=istr[1].begin();        string::const_iterator en=istr[1].end();        while(regex_search(st,en,rsm3,rr3)){            if(rsm3.str()!=","){                cout<<rsm3.str()<<endl;                vinsert2.push_back(rsm3.str());            }            st=rsm3[0].second;        }        Vinsert.push_back(vinsert2);    }else{        cout<<"检查values语句后是否存在错误！！！"<<endl;        return false;    }    result=Vinsert;    return true;}bool SqlEx::ForCreate(){    vector<vector<string>> Create;    regex re1("(?<=create table )\.+?(?=\\()");    regex re2("(?<=\\()\.+(?=\\))");     smatch csm1;     smatch csm2;     string cstr[2];     if(regex_search(Ex,csm1,re1)){        vector<string>create1;        cstr[0]=csm1.str();        cout<<"create table:"<<endl;        cout<<cstr[0]<<endl;        cout<<endl;        create1.push_back(cstr[0]);        Create.push_back(create1);     }else{        cout<<"检查create table语句后是否存在错误！！！"<<endl;        return false;    }     if(regex_search(Ex,csm2,re2)){        cstr[1]=csm2.str();        regex rer("(\.+?,)|(\.+)");        smatch rsm;        string::const_iterator st=cstr[1].begin();        string::const_iterator en=cstr[1].end();        while(regex_search(st,en,rsm,rer)){            string ss=rsm.str();            bool isname=true;            bool isatt=false;            bool iscap=false;            string name="";            string attribute="";            string capacity="";            vector<string> create1;            for(int i=0;i<ss.length();i++){                if(isname==true&&ss[i]!=' '){                    name = name+ss[i];                }                if(isname==true&&name!=""&&ss[i]==' '){                    isname=false;                    isatt=true;                    cout<<name<<endl;                    create1.push_back(name);                }                if(isatt==true&&ss[i]!=' '&&ss[i]!='('){                    attribute=attribute+ss[i];                }                if(isatt==true&&attribute!=""&&ss[i]=='('){                    isatt=false;                    iscap=true;                    cout<<attribute<<endl;                    create1.push_back(attribute);                }                if(iscap==true&&ss[i]!=' '&&ss[i]!='('&&ss[i]!=')'){                    capacity=capacity+ss[i];                }                if(iscap==true&&ss[i]==')'&&capacity!=""){                    iscap=false;                    cout<<capacity<<endl;                    create1.push_back(capacity);                }            }            Create.push_back(create1);            cout<<endl;            st=rsm[0].second;        }     }else{            cout<<"检查括号中语句是否存在错误！！！"<<endl;            return false;        }    result=Create;    return true;}bool SqlEx::ForSelect(){    vector<vector<string>> Select;    regex reg1("(?<=select )\.+?(?= from)");    regex reg2("((?<=from )\.+?(?= where))|((?<=from )\.+?(?=END))");    regex reg3("(?<=where )\.+?(?=END)");    smatch ssm[3];    if(regex_search(Ex,ssm[0],reg1)){            cout<<"select:"<<endl;        vector<string> attribute;        string stt="";        string ss=ssm[0].str();        for(int i=0;i<ss.size();i++){            if(ss[i]!=' '&&ss[i]!=','){                stt=stt+ss[i];            }            if((ss[i]==','||i==ss.size()-1)&&stt!=""){                cout<<stt<<endl;                attribute.push_back(stt);                stt="";            }        }        Select.push_back(attribute);    }else{            cout<<"检查select from语句后是否存在错误！！！"<<endl;            return false;        }    if(regex_search(Ex,ssm[1],reg2)){            cout<<"from:"<<endl;        vector<string> tablename;        string stt="";        string ss=ssm[1].str();        for(int i=0;i<ss.size();i++){            if(ss[i]!=' '&&ss[i]!=','){                stt=stt+ss[i];            }            if((ss[i]==','||i==ss.size()-1)&&stt!=""){                cout<<stt<<endl;                tablename.push_back(stt);                stt="";            }        }        Select.push_back(tablename);    }else{            cout<<"检查from语句后是否存在错误！！！"<<endl;            return false;        }    if(regex_search(Ex,ssm[2],reg3)){        vector<string>condition;        cout<<"where:"<<endl;        string sst =ssm[2].str();        regex sr("(\.+?and )|(\.+?or )");        smatch srsm;        string::const_iterator st=sst.begin();        string::const_iterator en=sst.end();        bool flag=false;        while(regex_search(st,en,srsm,sr)){            flag =true;            cout<<srsm.str()<<endl;            condition.push_back(srsm.str());            st=srsm[0].second;        }        if(flag){                regex_search(st,en,srsm,regex("\.+"));                cout<<srsm.str()<<endl;                condition.push_back(srsm.str());        }        else{                cout<<sst<<endl;                condition.push_back(sst);        }        Select.push_back(condition);    }    result=Select;    return true;}bool SqlEx::ForDrop(){    vector<vector<string>>drop;    regex dre("(?<=drop table )\\w+(?=END)");    smatch dsm;    cout<<"drop table:"<<endl;    if(regex_search(Ex,dsm,dre)){        cout<<dsm.str()<<endl;        vector<string> name;        name.push_back(dsm.str());        drop.push_back(name);    }else{            cout<<"检查drop语句后是否存在错误！！！"<<endl;            return false;        }    result=drop;    return true;}vector<vector<string>>SqlEx::getResult(){    return result;}string SqlEx::sql(string sql)//语句预处理{        const int count=sql.size();        string b="";        int flag=0;//标记        int n=0;        for(int i=0;i<count;i++)        {                if(sql[i]!=' ')                {                        b+=sql[i];                        n++;                        flag=1;                }                else if(sql[i]==' '&&flag==1)                {                        b+=sql[i];                        n++;                        flag=0;                }        }        if(b[n-1]==' ')              b.erase(n-1,1);        return b;}

#include <iostream>#include <fstream>#include <string>#include <vector>#include "SQLexpression.h"//#define otherint main(){    #ifndef other    std :: string str="";    do{        getline(std :: cin,str);        SqlEx se(str);        if(se.check()){            vector vec = null;                    string vec=se.getResult();                     for(int i=0;i<vec.size();i++){                for(int j=0;j<vec[i].size();j++){                    cout<<vec[i][j]<<endl;                }                cout<<endl;            }*/        }    }while(str!="#");    return 0;}