编译原理 lex/yacc实现简易sql解释器——词法分析，附代码

简介

SQL解释器功能：基本增删改查

基本功能基本都有，词法分析存在的问题应该不大。可以参考
终结符如下

%left OR
%left AND
%right NOT
%nonassoc '=' '>' '<'
%left '+','-'
%left '*','/'
%term CREATE TABLE CHAR INT  DATABASE USE SHOW DATABASES  
%term EXIT QUIT DROP TABLE TABLES INSERT INTO VALUES 
%term SELECT FROM WHERE FALSE TRUE AND NOT OR  DELETE UPDATE SET 
%term<yych> ID NUMBER STRING

数字以char*数组存储，用的时候转换一下

%{
#include "mysql4yacc.h"
#include
#include
char* stop;
%}
digit [0-9]
digits {digit}+
%%
[ ]+  {}
[\n]+  {}
"CREATE" {return CREATE;}
"DATABASE"  {return DATABASE;}
"USE"  {return USE;}
"SHOW"  {return SHOW;}
"DATABASES" {return DATABASES;}
"DROP"  {return DROP;}
"TABLE"  {return TABLE;}
"TABLES" {return TABLES;}
"INT"  {return INT;}
"CHAR"  {return CHAR;}
"INSERT" {return INSERT;}
"INTO"  {return INTO;}
"VALUES" {return VALUES;}
"SELECT" {return SELECT;}
"FROM"  {return FROM;}
"WHERE"  {return WHERE;}
"AND"  {return AND;}
"OR"  {return OR;}
"NOT"  {return NOT;}
"TRUE"  {return TRUE;}
"FALSE"  {return FALSE;}
"DELETE" {return DELETE;}
"UPDATE" {return UPDATE;}
"SET"  {return SET;}
"EXIT"  {return EXIT;}
"QUIT"  {return QUIT;}
"("   {return '(';}
")"   {return ')';}
","   {return ',';}
";"   {return ';';}
"+"   {return '+';}
"-"   {return '-';}
"*"   {return '*';}
"/"   {return '/';}
">"   {return '>';}
"<"   {return '<';}
"="   {return '=';}
"!"   {return '!';} 
"\'"  {return '\'';}
{digits} {
   yylval.yych=(char*)malloc(strlen(yytext)+1);
   strcpy(yylval.yych,yytext);
   return NUMBER;
   }
   
[a-zA-Z][a-zA-Z0-9_]* 
   {
   yylval.yych=(char*)malloc(strlen(yytext)+1);
   strcpy(yylval.yych,yytext);
   return ID;
   }
[a-zA-Z0-9_]* 
   {
   yylval.yych=(char*)malloc(strlen(yytext)+1);
   strcpy(yylval.yych,yytext);
   return STRING;
   }
%%

yacc中字符串应该这样写

string :   '\'' STRING '\''
   | '\'' ID '\''
   | '\'' NUMBER '\''
   ;

最好设置一下不区分大小写

https://blog.csdn.net/D1124615130/article/details/106528532

可能用到的C语言输入输出函数的简单介绍

https://blog.csdn.net/D1124615130/article/details/106785256