MySql执行动态表达式函数

执行动态的字符串表达式

1.支持加（+）、减（-）、乘（*）、除（/）、与（&&）、或（||）、非（!）、等于（=）、不等于（!= <>）、大于（>）、大于等于（>=）、小于（<）、小于等于（<=）

2.非的优先级高于其他运算符，其他运算符优先级相同，可以通过括号来控制运算的先后顺序

3.除运算符、括号、空格外，只能包含数字和小数点

/*二目运算*/
DROP FUNCTION compute;
DELIMITER $$
CREATE FUNCTION compute(v1 DOUBLE, o CHAR(2), v2 DOUBLE) RETURNS DOUBLE
BEGIN
IF(o = '+')
THEN
RETURN v1 + v2;
ELSEIF(o = '-')
THEN
RETURN v1 - v2;
ELSEIF(o = '*')
THEN
RETURN v1 * v2;
ELSEIF(o = '/')
THEN
RETURN v1 / v2;
ELSEIF(o = '=')
THEN
RETURN v1 = v2;
ELSEIF(o = '!=')
THEN
RETURN v1 != v2;
ELSEIF(o = '&&')
THEN
RETURN v1 AND v2;
ELSEIF(o = '||')
THEN
RETURN v1 OR v2;
ELSEIF(o = '>')
THEN
RETURN v1 > v2;
ELSEIF(o = '>=')
THEN
RETURN v1 >= v2;
ELSEIF(o = '<')
THEN
RETURN v1 < v2;
ELSEIF(o = '<=')
THEN
RETURN v1 <= v2;
ELSE
RETURN 0;
END IF;
END;
$$
DELIMITER ;

/*执行表达式*/
DROP FUNCTION eval;
DELIMITER $$
CREATE FUNCTION eval(express VARCHAR(2000)) RETURNS DOUBLE
BEGIN
DECLARE hasValue TINYINT;
DECLARE r DOUBLE;/*结果*/
DECLARE l INT;
DECLARE i INT;
DECLARE lt INT;/*临时*/
DECLARE it INT;/*临时*/
DECLARE c CHAR;/*当前字符*/
DECLARE t CHAR;/*双字操作符前一个字符*/
DECLARE tt VARCHAR(200); /*临时*/
DECLARE o VARCHAR(20); /*操作符*/
DECLARE v VARCHAR(20); /*值*/
DECLARE v1 DOUBLE;/*结果*/
DECLARE v2 DOUBLE;/*结果*/

DECLARE stack VARCHAR(4000); /*堆栈*/
/*DECLARE _log VARCHAR(2000);*/ /*临时*/

DECLARE fc INT;/*搜索括号计数*/
DECLARE fi INT;/*搜索括号指针*/
SET r = 0;
SET hasValue = 0;

SET l = LENGTH(express);
SET i = 1;
SET t = '';
SET v = '';
SET o = '';
set stack = '';
/*set _log = '';*/

_loop : LOOP
IF(i > l)
THEN
SET c = '';
ELSE
SET tt = SUBSTRING(express, i, 1);
SET c = if(tt = ' ', 'S', tt);
END IF;
/*set _log = concat(_log, ',char:[', c,',', v,']');*/
IF(c = '')
THEN /*表达式结束*/
IF(v != '')
THEN
SET v2 = v;
set v = '';
IF (o != '')
THEN
IF (hasValue = 0)
THEN
IF (o = '-')
THEN
SET r = -v2;
ELSE
/*无前操作数*/
/*set _log = concat(_log, ',no v1');*/
set r = NULL;
set i = l + 1;
END IF;
SET hasValue = 1;
ELSE
SET r = compute(r, o, v2);
END IF;
ELSEIF (hasValue = 0)
THEN
SET r = v2;
SET hasValue = 1;
ELSE
/*无操作符*/
set r = NULL;
set i = l + 1;
END IF;
ELSEIF (o != '' OR t = '!' OR t = '<' OR t = '〉' OR t = '&' OR t = '|')
THEN
/*无后操作数或操作符不全*/
/*set _log = concat(_log, ',error operator');*/
set r = NULL;
set i = l + 1;
END IF;
ELSEIF (c = ')')
THEN
/*未匹配的右括号*/
set r = NULL;
set i = l + 1;
ELSE
IF (v != '' AND LOCATE(c,'0123456789.') = 0)
THEN
/*set _log = concat(_log, ',charEnd:[', v,']');*/
/*数字结束*/
SET v2 = v;
set v = '';
IF (o != '')
THEN
IF (hasValue = 0)
THEN
IF (o = '-')
THEN
SET r = -v2;
ELSE
/*无前操作数*/
/*set _log = concat(_log, ',no v1');*/
set r = NULL;
set i = l + 1;
END IF;
SET hasValue = 1;
ELSE
SET r = compute(r, o, v2);
END IF;
SET o = '';
ELSEIF (hasValue = 0)
THEN
SET r = v2;
SET hasValue = 1;
ELSE
/*无操作符*/
/*set _log = concat(_log, ',no operator');*/
set r = NULL;
set i = l + 1;
END IF;
END IF;

if(i <= l)
then
IF (t = '!' AND c != '=' OR t = '<' AND c != '>' AND c != '=' OR t = '>' AND c != '=') /*非、大于、小于*/
THEN

/*set _log = concat(_log, ',check !><');*/
if(o != '' and t != '!')
then
/*多余的操作数*/
/*set _log = concat(_log, ',otiose operator[',o,']');*/
set r = NULL;
set i = l + 1;
else
/*搜索下一个表达式或者值*/
SET fc = 0;
SET fi = i;
SET tt = '';
SET v = '';
WHILE (fi <= l AND (tt = '' OR fc > 0))
DO
SET c = SUBSTRING(express,fi, 1);
IF (c = '(')
THEN
SET tt = '(';
SET fc = fc + 1;
ELSEIF (c = ')')
THEN
SET fc = fc - 1;
ELSEIF (tt = '' AND LOCATE(c, '0123456789.'))
THEN
SET tt = '0';
SET fc = 1;
ELSEIF (tt = '0' AND LOCATE(c, '0123456789.') = 0)
THEN
SET fc = 0;
SET fi = fi - 1;
END IF;
SET fi = fi + 1;
END WHILE;

IF (fc = 0 OR tt = '0')
THEN
/*当前状态入栈，并初始化变量*/
set stack = concat(stack ,'$',hasValue,',',ifnull(r, ''),',',o,',',t,',',l,',',fi);
/*set _log = concat(_log, ',not:',substring(express, i, fi - i), ',push:[',hasValue,',',ifnull(r, ''),',',o,',',t,',',l,',',fi,']');*/
set i = i;
set l = fi - 1;
set hasValue = 0;
set r = 0;
set t = '';
SET o = '';
set v = '';

/*开始新的循环*/
ITERATE _loop;
ELSE
/*没有找到操作数*/
/*set _log = concat(_log, ',no value');*/
set r = NULL;
set i = l + 1;
END IF;
END if;
ELSEIF (c = '(')
THEN
/*寻找匹配的)*/
SET fc = 1;
SET i = i + 1;
SET fi = i;
WHILE (fi <= l AND fc > 0)
DO
SET c = SUBSTRING(express,fi, 1);
IF (c = '(')
THEN
SET fc = fc + 1;
ELSEIF (c = ')')
THEN
SET fc = fc - 1;
END IF;
SET fi = fi + 1;
END WHILE;

IF (fc = 0)
THEN

/*当前状态入栈，并初始化变量*/
set stack = concat(stack ,'$',hasValue,',',ifnull(r, ''),',',o,',','',',',l,',',fi);
/*set _log = concat(_log, ',sub:',substring(express, i, fi - 1 - i), ',push:[',hasValue,',',ifnull(r, ''),',',o,',',t,',',l,',',fi,']');*/
set i = i;
set l = fi - 2;
set hasValue = 0;
set r = 0;
set t = '';
SET o = '';
set v = '';

/*开始新的循环*/
ITERATE _loop;
ELSE /*没有找到匹配的右括号*/
/*set _log = concat(_log, ',no )');*/
set r = NULL;/*无操作符*/
set i = l + 1;
END IF;
ELSEIF (LOCATE(c, '0123456789.') > 0)
THEN
/*找到数字*/
IF (v = '')
THEN
/*set _log = concat(_log, ',char:',c);*/
SET v = c;
ELSE
/*set _log = concat(_log, ',concat:',c);*/
SET v = CONCAT(v, c);
END IF;
ELSEIF(LOCATE(c,'!<>|&=+-*/'))
THEN
SET tt = '';
IF (t = '!' AND c = '=')
THEN
SET tt = '!=';
ELSEIF (t = '<' AND c = '>')
THEN
SET tt = '!=';
ELSEIF (t = '|' AND c = '|')
THEN
SET tt = '||';
ELSEIF (t = '&' AND c = '&')
THEN
SET tt = '&&';
ELSEIF (t = '' AND c = '=')
THEN
SET tt = '=';
ELSEIF (t = '>' AND c = '=')
THEN
SET tt = '>=';
ELSEIF (t = '<' AND c = '=')
THEN
SET tt = '<=';
ELSEIF (t = '' AND c = '+')
THEN
SET tt = '+';
ELSEIF (t = '' AND c = '-')
THEN
SET tt = '-';
ELSEIF (t = '' AND c = '*')
THEN
SET tt = '*';
ELSEIF (t = '' AND c = '/')
THEN
SET tt = '/';
END IF;

IF (o != '' AND tt != '')
THEN
/*set _log = concat(_log, ',otiose operator');*/
set r = NULL; /*多个操作符*/
set i = l + 1;
ELSEIF (tt != '')
THEN
SET o = tt;
SET t = '';
ELSEIF (c = '!' OR c = '<' OR c = '>' OR c = '&' OR c = '|')
THEN
IF(t = '')
THEN
SET t = c;
ELSE
/*set _log = concat(_log, ',no operator');*/
set r = NULL; /*错误的操作符*/
set i = l + 1;
END IF;
END IF;
ELSEIF(LOCATE(c, ' S\r\n\t') = 0)
THEN
/*set _log = concat(_log, ',error char');*/
set r = NULL; /*无效字符*/
set i = l + 1;
END IF;
END IF;
END IF;

SET i = i + 1;
if(i > l + 1)
then
if (stack != '') /*堆栈未空，返回上一层*/
then
set l = 0;
repeat
set l = locate('$',stack, l + 1);
if(l != 0)
then
set i = l;
end if;
until l = 0 end repeat;

set tt = substring(stack, i + 1);
set stack = substring(stack, 1, i - 1);
/*set _log = concat(_log, ',pop:[', tt,'],stack:[',stack,']');*/
/*恢复上一层环境，并计算 concat('$',hasValue,',',v1,',',o,',',t,',',l,',',fi - 1);*/
set i = 1;
set it = 1;
set lt = 0;
repeat
set lt = locate(',',tt, lt + 1);
if(i = 1)
then
set hasValue = substring(tt, it, lt - it);
elseif(i = 2)
then
set v1 = substring(tt, it, lt - it);
elseif(i = 3)
then
set o = substring(tt, it, lt - it);
elseif(i = 4)
then
set t = substring(tt, it, lt - it);
elseif(i = 5)
then
set l = substring(tt, it, lt - it);
elseif(i = 6)
then
set i = substring(tt, it);
end if;

if(lt != 0)
then
set it = lt + 1;
set i = i + 1;
end if;
until lt = 0 end repeat;

/*set _log = concat(_log, ',parse:[',hasValue,',',v1,',',o,',',t,',',l,',',i,']');*/

if(t = '!')
then
set r = not r;
elseif(t != '')
then
set o = t;
end if;
set t = '';

IF (o != '')
THEN
IF (hasValue = 0)
THEN
IF (o = '-')
THEN
SET r = -r;
ELSE
SET r = NULL;
END IF;
SET hasValue = 1;
ELSE
SET r = compute(v1, o, r);
END IF;
SET o = '';
ELSEIF (hasValue = 0)
THEN
SET hasValue = 1;
ELSE
/*无操作符*/
set r = NULL;
set i = l + 1;
END IF;
/*set _log = concat(_log, ',r=', ifnull(r, 'null'));*/
else
LEAVE _loop;
end if;
end if;
END LOOP;

/*set _log = concat('r=',ifnull(r, 'null'),_log);*/
RETURN r;
END;
$$
DELIMITER ;